Clinical activity of pembrolizumab in refractory MDM2-amplified advanced intimal sarcomas

Intimal sarcoma (InS) is an ultra-rare and aggressive subtype of soft tissue sarcoma (STS). It usually arises in large mediastinal arteries and the heart. In the advanced setting, sequential cytotoxic chemotherapy is often used, mainly based on retrospective studies and case series but with modest benefit. The use of immune checkpoint inhibitors is a promising strategy for some STS, but identifying biomarkers of response remains challenging due to disease rarity and heterogeneity. A reactive and pro-inflammatory tumor microenvironment (TME) is believed to be associated with better outcomes for patients receiving anti-PD-1-based regimens, generating the rationale to explore this strategy in malignancies with this characteristic, such as InS. We report three cases of advanced InS patients experiencing partial response to pembrolizumab-based therapy despite low tumor mutational burden and absence of mismatch-repair deficiency. We hypothesize that TME-related characteristics such as PD-L1 expression and the presence of tertiary lymphoid structures might explain this phenomenon.

Clinico-demographic characteristics and outcomes of radiation-induced sarcomas (RIS): a CanSaRCC study

Background

Radiation-induced sarcomas (RIS) tend to have aggressive behaviour and because of their rarity, the most appropriate management for these malignancies is uncertain.

Objectives

Using the Canadian Sarcoma Research and Clinical Collaboration (CanSaRCC) database, a national sarcoma registry, we aimed to investigate prognostic factors and outcomes for RIS.

Design

Retrospective study of RIS patients treated from 1996 to 2021 at three Canadian centres.

Methods

RIS was defined as a sarcoma arising in a previously irradiated field following a 3+ year latency period, whose histology was distinct from the initially irradiated tumour. Clinicopathologic and treatment-related information was extracted from the CanSaRCC database. Overall survival (OS) was defined as the time from RIS diagnosis to death from any cause. Response rate (RR) to neoadjuvant chemotherapy (NACT) was based on physician assessment. Time-to-event analyses were estimated using the Kaplan-Meier method, with Cox regression for multivariate analysis. We considered a two-tailed p-value of <0.05 as statistically significant.

Results

One hundred seven tumours met the criteria for RIS and were divided into three subgroups: breast angiosarcoma (BAS, n = 54), osteosarcoma (OST, n = 16), and other soft-tissue sarcomas (STS, n = 37). Patients were mostly female (n = 85, 79%), treated initially for breast carcinomas (n = 54, 50.5%), and diagnosed with high-grade tumours (n = 61/71, 86%). None had evidence of synchronous metastasis. Patients with OST were younger (median age: 48 years, p < 0.001), and BAS had the shortest latency interval (8 versus 18 years for OST/STS, p < 0.001). Most patients underwent surgery, 76% (n = 76/100) R0; 24% (n = 26) received radiation therapy, mostly (n = 15, 57.7%) neoadjuvant. Among those receiving chemotherapy, 30 (75%) underwent NACT; among patients with documented response assessment, the RR was 68% (n = 17/25), being even higher in the BAS population (89.5%, n = 13/17). Median OS was 53 months (95% CI 34-101), with a 5-year OS of 47.6%; larger tumour size, high histologic grade and older age were independent prognostic factors for worse OS.

Conclusion

Surgery is standard, and NACT might be useful to downsize large lesions, especially in BAS patients. Raising RIS awareness is fundamental to promoting appropriate management and fostering research through multi-institutional collaborations.

Mutational heterogeneity of imatinib resistance and efficacy of ripretinib vs sunitinib in patients with gastrointestinal stromal tumor: ctDNA analysis from INTRIGUE

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Background: Ripretinib, a switch-control tyrosine kinase inhibitor (TKI), is indicated for patients (pts) with gastrointestinal stromal tumor (GIST) who received prior treatment with ≥3 TKIs, including imatinib. Sunitinib is approved for advanced GIST after imatinib failure. Circulating tumor DNA (ctDNA) analysis may provide insight into the efficacy of these agents in second-line advanced GIST. Here, we present exploratory baseline ctDNA results from INTRIGUE. Methods: INTRIGUE is an open-label, phase 3 study that enrolled adult pts with advanced GIST who progressed on or had intolerance to imatinib (NCT03673501). Randomization was 1:1 to ripretinib 150 mg once daily (QD) or sunitinib 50 mg QD (4 wks on/2 wks off). Baseline peripheral whole blood was analyzed by Guardant360, a 74-gene ctDNA next-generation sequencing (NGS)-based assay. Only KIT mutations are reported here. Results: Of 453 pts in the overall intent-to-treat (ITT) population, 362 (80%) samples were analyzed. ctDNA was detected in 280/362 (77%), with KIT mutations detected in 213/280 (76%). Common resistance mutations were in the KIT activation loop (AL; exons 17/18; 89/213, 42%) and ATP-binding pocket (ATP-BP; exons 13/14; 81/213, 38%). Efficacy in pts with detectable ctDNA in the KIT exon 11 and overall ITT populations was consistent with the primary analysis based on tumor data used for randomization. Pts with KIT exon 11 + 17/18 (−9/13/14) mutations had superior progression-free survival (PFS), objective response rate (ORR), and overall survival (OS) with ripretinib vs sunitinib, whereas pts with exon 11 + 13/14 (−9/17/18) mutations had better PFS, ORR, and OS with sunitinib vs ripretinib (Table). Subgroup safety profiles were consistent with the primary analysis. Conclusions: While KIT ATP-BP mutations predicted clinical benefit from sunitinib vs ripretinib, pts harboring resistance mutations in the KIT AL derived meaningful clinical benefit from ripretinib but not sunitinib. This study demonstrates the value of ctDNA NGS-based sequencing of the complex landscape of KIT mutations to predict the clinical benefit of ripretinib or sunitinib as second-line therapy in pts with advanced GIST. Clinical trial information: NCT03673501 . [Table: see text]

Abstract A038: Enrollment of pediatric and adolescent patients with MAGE-A4+ advanced synovial sarcoma into cohort 2 of SPEARHEAD-1: a phase 2 trial of afamitresgene autoleucel (“afami-cel” [formerly ADP-A2M4])

Background: Afami-cel is an autologous, specific peptide enhanced affinity receptor T-cell therapy genetically engineered to target MAGE-A4+ solid tumors in HLA-A*02+ patients. SPEARHEAD-1 (NCT04044768) is a Phase 2, two-cohort, single-arm, open-label trial evaluating afami-cel in patients with advanced/metastatic synovial sarcoma or myxoid/round cell liposarcoma (MRCLS) and is the largest trial in metastatic synovial sarcoma to date. Preliminary data from Cohort 1 in 47 heavily pre-treated patients aged 16–75 years from 22 centers in North America and Europe, showed an overall response rate (ORR) per independent review of 34.0% (14/39 [35.9%] in synovial sarcoma; 2/8 [25%] in MRCLS) and a favorable benefit–risk profile with mainly low-grade cytokine release syndrome and tolerable/reversible hematologic toxicities.1 The reported ORR in synovial sarcoma in Cohort 1 was higher than reported ORRs for current standard-of-care therapies, such as pazopanib and trabectedin, in the second-line metastatic setting.2 As synovial sarcoma is the most common malignant nonrhabdomyosarcoma soft-tissue sarcoma in children and adolescents with few treatment options, especially for recurrent disease, the trial opened a second cohort to allow enrollment of pediatric patients with MAGE-A4+ synovial sarcoma who experienced disease progression post first-line chemotherapy, and to better understand MAGE-A4 tumor expression in children. Methods: Cohort 2 of the SPEARHEAD-1 trial is enrolling patients with advanced synovial sarcoma who are at least 10 years old and weigh at least 40 kg. The planned enrollment is 45 patients, including up to 13 children, to enable a pooled analysis of ORR in &gt;90 patients across Cohorts 1 and 2. HLA and MAGE-A4+ screening in Cohort 2 is conducted at a central laboratory using the same method as Cohort 1; MAGE-A4 testing is done using a clinical trial assay. All patients enrolled in Cohort 2 undergo apheresis and their isolated T-cells are then transduced with the MAGE-A4c1032 TCR using a lentivirus vector, followed by ex vivo expansion. Prior to afami-cel infusion of 1–10 × 109 transduced T-cells, patients will receive lymphodepleting chemotherapy consisting of fludarabine (30 mg/m2/day for 4 days) and cyclophosphamide (600 mg/m2/day for 3 days). Disease will be assessed by independent review per RECIST v1.1 using computerized tomography or magnetic resonance imaging at weeks 4, 8, 12, 16, 24, and every 2 months thereafter until confirmed disease progression. Patients enter long-term follow-up for 15 years. 1. Van Tine BA, et al. Paper 30: CTOS 2021; Virtual 2. Carroll C, et al. Cancer Res 2021;81(13_Suppl): Abstract nr 2630.

Citation Format: Colin Lunt, Sandra P. D’Angelo, Albiruni Ryan Abdul Razak, Michael J. Wagner, Brian A. Van Tine, Kristen Ganjoo, Jean-Yves Blay, Dejka M. Araujo, Mark Agulnik, John W. Glod, Erin Van Winkle, Erica Elefant, Swethajit Biswas, Dennis Williams, Axel Le Cesne. Enrollment of pediatric and adolescent patients with MAGE-A4+ advanced synovial sarcoma into cohort 2 of SPEARHEAD-1: a phase 2 trial of afamitresgene autoleucel (“afami-cel” [formerly ADP-A2M4]) [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr A038.

Circulating tumor DNA (ctDNA) detection of molecular residual disease (MRD) as a potential biomarker in localized soft tissue sarcoma (STS)

11547

Background: Surgery and (neo)adjuvant radiotherapy are the mainstay curative treatments for localized STS. Despite treatment, approximately 50% of STS patients (pts) experience metastatic relapse and routine use of adjuvant systemic therapy (AST) remains controversial. The presence of ctDNA following curative treatment of STS is a potential biomarker for MRD and may identify patients who benefit from AST. Given the genomic heterogeneity of STS, a histology-agnostic approach to ctDNA detection in this population is desirable. Methods: Pts with localized, high risk (size ≥ 5cm, grade ≥ 2) disease were enrolled prior to (neo) adjuvant radiotherapy and surgery. Blood for ctDNA was collected at diagnosis; post-radiotherapy, post-surgery and every 3 months for up to 2 years. Whole exome sequencing (WES) of archival tumor- and matched buffy coat-DNA were carried out to identify somatic variants. Personalized and tumor-informed, multiplex PCR next generation sequencing-based ctDNA assay (Signatera™ assay) was performed on plasma obtained at the serial timepoints. A sample level positive call required ≥ 2 variants above a confidence calling threshold. Absolute ctDNA levels were expressed as mean tumor molecules per milliliter (MTM/ml) of plasma, based on variant allele frequencies and quantity of cell free DNA. Standard radiologic surveillance (every 3 months) was performed following surgery. The primary endpoint was a ctDNA detection rate of 70% at diagnosis. Secondary endpoints included MRD detection and correlation of ctDNA levels with disease relapse. Results: Seventy-six plasma samples from 10 pts [8 males and 2 females; median age 64 years (range 46–84)] were obtained prospectively. STS subtypes were undifferentiated pleomorphic sarcoma (n = 4), myxofibrosarcoma (n = 2), dedifferentiated liposarcoma (n = 2), myxoid liposarcoma (n = 1), and pleomorphic liposarcoma (n = 1). All tumors successfully underwent WES with adequate data quality for Signatera™ assay design. The personalized ctDNA assay was performed on a median of 7 plasma samples per patient (range: 5 – 10). ctDNA was detected in 7 pts (70%) at diagnosis, with median ctDNA level of 1.6 MTM/ml (range: 0.2 – 137.8), achieving the study primary endpoint. Immediate post-surgery samples were negative in all pts. However, ctDNA was detected in 2 out of 2 pts who developed metastatic disease during follow-up. Conclusions: Personalized tumor-informed ctDNA assays in localized high-risk STS at diagnosis are feasible. In this series, all patients had undetectable levels of ctDNA post-surgery and patients who experienced disease relapse demonstrated a detectable rise in ctDNA levels. Further interrogation of this approach for detection of post-treatment MRD as a possible biomarker of benefit from AST is ongoing.

Early circulating tumor DNA (ctDNA) kinetics using a tumor-naïve assay as a predictive biomarker in early-phase immunotherapy (IO) clinical trials

2546

Background: ctDNA kinetics with tumor-informed assays can predict treatment outcome in patients (pts) treated with anti-PD1 IO ( Bratman et al, Nature Cancer 2020). We evaluated whether early ctDNA kinetics with a tumor-naïve assay were associated with clinical outcomes in advanced solid tumor patients treated on early phase IO trials. Methods: Advanced solid tumor pts treated with investigational IO agents at the Princess Margaret Phase I program were enrolled. Baseline (B) and pre-cycle 2 (C2) (3-4 weeks after first dose) plasma samples were prospectively collected via an institutional liquid biopsy program (LIBERATE, NCT03702309). ctDNA was assessed using the tumor-naïve 425-gene Geneseeq Prime panel in a clinical laboratory. Mutations in each gene detected in ctDNA were measured as Variant Allele Fraction (VAF). Mean VAF from all mutations was calculated. Radiological response was measured per RECIST criteria and correlated using ROC curves. Hyperprogression (HPD) was defined using VHIO criteria ( Matos et al, CCR 2020). Survival outcomes were estimated using the Kaplan Meier method. Results: From 12/2017 to 3/2020, 162 plasma samples from 81 pts with 25 different tumor types were collected. Pts were treated within 25 different IO phase I/II trials, 72% of which involved a PD-1/PD-L1 inhibitor. Median age was 58y (range 21 – 79), 54% female, 76% ECOG1. Sarcoma and colorectal (11%, each) followed by breast (8%) and melanoma (7%) were the most frequent tumors. Median follow up was 10.3 months (m) (1.8-46.9). CR 4% (n = 3), PR 6% (n = 5), HPD 11% (n = 9). Clinical benefit (CB) rate (CR+PR+SD > 6 months) was 20% (n = 16). ctDNA was detected in 122/162 samples (75.3%) (60 at B, 62 at C2). The most frequent mutations were TP53 (32%), PI3KCA (12%), PKHD1 (11%), and KRAS (9%). Mean VAF at B below median was not associated with OS (HR = 0.68 95%CI 0.4-1.16; p = 0.16) or PFS (HR = 0.93 95%CI 0.56-1.54; p = 0.77). Mean VAF change (difference between mean VAF at B and at C2) was associated with response (AUC = 0.99) and CB (AUC = 0.86). A decrease in mean VAF from B to C2 was seen in 24 pts (37.5%) and was associated with longer PFS (median PFS 2.7 vs 1.8 m; HR: 0.43, 95%CI 0.24-0.77; p < 0.01) and OS (median OS 10.8 vs 9.1 m; HR: 0.54; 95%CI 0.3-0.96; p = 0.03) compared to an increase in mean VAF. These differences were more marked if there was > 50% decrease in mean VAF from B to C2 (n = 11, 17%) compared to decrease < 50% or increase: median PFS 3.6 vs 1.8 m (HR: 0.29, 95%CI 0.13-0.62; p < 0.01) and median OS not reached vs 9.6 m (HR: 0.23, 95%CI 0.09-0.6; p < 0.01). No differences in mean VAF change were seen between HPD and PD pts. Conclusions: In a pan-cancer solid tumor early phase trial IO cohort, a decrease in ctDNA within 4 weeks of treatment was associated with increased CB, OS and PFS. HPD pts did not show greater increases in ctDNA. Tumor-naïve ctDNA assays may be useful to identify early treatment benefit in phase I/II trials with IO.

Do early phase trials predict clinical efficacy in subsequent phase III biomarker-enriched randomized trials?

3152

Background: Efficacy endpoints of randomized controlled trials (RCT) are commonly used as the basis of regulatory drug approvals. Recently, promising results in early phase trials have resulted in approval of biomarker-targeted therapies. We examined if early phase trial results were associated with efficacy in subsequent biomarker-enriched RCTs. Methods: All cancer drug RCTs conducted between January 2006 and March 2021 were identified through Clinicaltrials.gov. Trials were eligible if a biomarker was used to select a patient population for treatment with a targeted agent. Associated early phase trials were included if they matched the RCT in treatment setting and patient population. Trials pairs were compared using objective response rate (ORR) and progression-free survival (PFS). We assessed difference in endpoints using summary measures (e.g., average, range). We examined whether early phase trials results were associated with RCT results using logistic regression. Results: The search yielded 2,157 unique phase III RCTs and 27 RCTs met eligibility criteria pairing with associated early phase trials, where 17 RCTs met their primary endpoint. The most common biomarkers were EGFR+ (n = 8), HER2+ (n = 5) and PD-L1 (n = 5). Based on average difference of trial pairs, ORR was similar between trials (1.59%, 95% CI = -2.5-5.6, p = 0.50) and median PFS was slightly higher in early phase trials (1.95 months, 95% CI = 0.91-2.99, p < 0.05). On an individual pair basis, there was large range of variability in the difference between early phase trials and RCTs for ORR (range = -23.9-20.2%) and median PFS (range = -0.8-7.4 months). The probability of the RCT meeting its primary endpoint is 50% or 95%, when the early phase trial ORR is 41.2% (95% CI = 35.2-47.1%) or 77.7% (95% CI = 71.7-83.6%), respectively. Conclusions: Through comparison of early phase trials and subsequent phase III RCT, we found that, overall, ORR has minimal bias in early phase trials, and median PFS appears to be slightly overestimated. Substantial variability in results for trial pairs suggests that, on an individual basis, results in early phase trial can be inconsistent with results in subsequent RCT. Early phase trial results may be associated with RCTs meeting their primary endpoint when ORR is very high; however, caution must be exercised when using early phase trials as representative of RCTs for decision-making as the predictive ability of early phase trials is limited.

Results of a phase I dose escalation and expansion study of tegavivint (BC2059), a first-in-class TBL1 inhibitor for patients with progressive, unresectable desmoid tumor

11523

Background: Desmoid tumors are known to have increased nuclear β-catenin levels. Tegavivint selectively disrupts the interaction of β-catenin and TBL1/ TBLR1, resulting in specific degradation of nuclear β-catenin. The primary objectives of this study were to determine the maximum tolerated dose (MTD), safety, and preliminary efficacy of tegavivint in patients (pts) with desmoid tumors. Methods: This study ( NCT03459469) utilized an accelerated dose escalation schema for the first two dose levels followed by a 3+3 design to determine the MTD/recommended phase 2 dose (RP2D) of tegavivint, followed by a dose expansion phase. The study included adult pts with sporadic desmoid tumors that were progressive (20% increase in tumor volume, recurrent in one year from surgery, or symptomatic), unresectable, and measurable via WHO criteria. Tegavivint was administered IV weekly (three weeks on, one week off) up to two years. Results: 24 pts were enrolled. Dose escalation enrolled 17 pts in six dose levels from 0.5 - 5 mg/kg. In dose expansion, 7 additional pts were enrolled. Dose expansion cohort also included 6 pts in dose escalation that were escalated to RP2D and 3 pts treated at RP2D in dose escalation (n = 16 total). Median age was 43 years (18-66). Median time from diagnosis was 3.1 years with median of one prior systemic treatment (range 0-6). Median time on study was 9.4 months; 3 pts remain on study at data cut-off. No dose-limiting toxicities were observed; MTD was not determined. RP2D was declared at 5 mg/kg based on pharmacologically relevant plasma concentrations and preliminary efficacy. Trough plasma concentrations (Cmin) exceeded in vitro IC50 efficacy estimates at 4 mg/kg and 5 mg/kg. Median half-life was 38 hours supporting once weekly administration. Treatment-related adverse events (TRAEs) occurring in ≥20% of pts included fatigue (71%), headache (38%), nausea (33%), constipation (21%), decreased appetite (21%), and dysgeusia (21%), mostly Grade 1-2. Grade 3 TRAEs of hypophosphatemia, stomatitis, increased ALT, diarrhea, and headache occurred in 5 separate pts. There were no grade 4-5 adverse events (AEs). One serious AE of Grade 2 extravasation occurred. Objective response rate (ORR) of 17% across all dose levels and 25% at RP2D (WHO and RECIST criteria) were observed. Median duration of response was 8.1 months (range 6 to 11.8 months) with all responses ongoing. The 9-month progression free survival rate was 76% (95% CI: 54 - 90%) among all pts and 79% (95% CI: 51 – 93%) among those treated at RP2D. Patient reported outcomes and correlative science will be included in the presentation. Conclusions: Tegavivint is well tolerated with mostly Grade 1/2 AEs and no serious toxicity associated with WNT inhibition. The ORR of 25% at the RP2D warrants continued development of tegavivint in desmoid tumors. Clinical trial information: NCT03459469.

Patient reported outcomes and tolerability in patients receiving ripretinib versus sunitinib after imatinib treatment in INTRIGUE: A phase 3 open-label study

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Background: Ripretinib (R) is a switch-control tyrosine kinase inhibitor (TKI) indicated for the treatment of patients (pts) with advanced gastrointestinal stromal tumor (GIST) after prior treatment with ≥3 TKIs. In the INTRIGUE study (NCT03673501) there was no significant difference in median PFS (primary endpoint) between R and sunitinib (S). We present exploratory analyses of tolerability data and selected pt reported outcomes (PROs). Methods: Pts were randomized 1:1 to R 150 mg QD or S 50 mg QD 4 weeks on/2 weeks off.Dose modification was allowed for toxicity management. The event of interest was severe or life-threatening (grade ≥3) treatment-related adverse event prior to progression (sTRAE). Days with at least one sTRAE were summed for all treated pts and for pts with ≥1 sTRAE event. PROs were assessed using questions from EORTC QLQ-C30 and Dermatology Life Quality Index (DLQI) at cycle 1 (C1) day 1 (D1), D15, and D29; D1 and D29 of all other cycles; as well as at end of treatment. Differences in PRO scores between baseline and later assessments were calculated across visits. Long-term data will be presented. Results: Pts receiving R (n = 223) versus (vs) S (n = 221) experienced fewer sTRAEs (24% vs 51%, respectively). For all treated pts, the mean time with sTRAEs was 11 days for R and 42 days for S (ratio 0.27, P<0.0001). For pts with ≥1 sTRAE, the mean number of days with a sTRAE was 48 days for R vs 81 days for S (ratio 0.59, p = 0.037). Completion of PRO assessments across the two treatment arms was similar (baseline: R [n = 199], S [n = 199]; C1 D29: R [n = 167], S [n = 177]). Significant differences in self-reported functioning and symptoms were observed by C1 D29. For PROs relating to commonly reported sTRAEs, except constipation, pts in the R arm reported better outcomes than pts in the S arm. Pts in the R arm reported significantly (p<0.05) less decline compared to baseline in pt-reported role function as well as less increase, or improvement, in symptoms of fatigue, appetite loss, diarrhea, nausea/vomiting, and pain vs pts in the S arm. Moderate or severe effect of skin toxicity on pt life, as measured by DLQI in the R arm (n = 165) and in the S arm (n = 175), was observed in 6.6% of pts in the R arm vs 14.8% of pts in the S arm (p = 0.015). Conclusions: In the INTRIGUE study the total number of days with sTRAEs was fewer for pts receiving R vs S. Pts in the R arm also reported significantly less decline in pt-reported role function and less increase in symptoms related to commonly reported sTRAEs, except constipation, vs pts in the S arm. Medical writing provided by Costello Medical. Clinical trial information: NCT03673501.

Customized autoantibodies (autoAbs) profiling to predict and monitor immune-related adverse events (irAEs) in patients receiving immune checkpoint inhibitors (ICI)

2528

Background: Using a customized microarray, we previously reported that patients (pts) who develop irAEs grade (G)≥2 and those who do not, have different median fluorescent intensity (MFI) levels of specific autoAbs at baseline (pre-ICI). Leveraging a larger dataset, we evaluated whether overall baseline autoAbs elevation and early increases in autoAbs after ICI can predict irAEs as well as if steroid treatment can reduce autoAbs. Methods: Plasma was obtained from pts receiving ICI in two clinical trials (MET4-IO, NCT03686202 and INSPIRE, NCT02644369) and from healthy controls (hc). Collection time points in MET4-IO and INSPIRE studies included: baseline, 3-4 weeks (w), 6-8 w, 24 w and at the end of treatment and baseline and 6 w respectively. Arrays with 162 autoAg customized for frequent irAEs were incubated with plasma and probed with Abs to detect IgG and IgM reactivity. AutoAbs with MFI >500 per individual were compared between hc and pts with and without irAEs G≥2 by the Student-t test. Results: Samples from 114 pts and 14 hc were analyzed (pts characteristics are summarized in the Table). G≥2 irAEs included: hypothyroidism (13), pneumonitis (10), colitis (7), hepatitis (4), skin toxicity (7), infusion reaction (2), pancreatitis (2), meningitis (1), hypophysitis (1), corneal ulcer (1), high creatinine (1), myocarditis (1), myositis (1), diabetes (1), mucositis (1), myasthenia (1) and adrenal failure (1). Hc had less autoAbs with MFI >500 as compared to pts at baseline (median 32 vs 62 p<0.001). IgG with MFI >500 were higher at baseline in pts who developed G≥2 irAEs vs those without G≥2 irAEs (median 39 vs 33, p=0.03). In 23 pts with plasma collected at the time of irAEs, we observed a significant increase of autoAbs with MFI>500 from baseline (median 84 vs 77 p= 0.009). Paired samples at the time of irAEs and after steroids were available for 9/23 pts, showing lower autoAbs after steroid treatment (54 vs 79 p=0.006). No differences in autoAbs with MFI>500 pre and post ICI were seen in pts without G≥2 irAEs (baseline vs first post ICI collection median 58 vs 60, p=0.13). Conclusions: We observed a higher number of IgG with MFI >500 at baseline and a greater increase after ICI administration in individuals with irAEs compared to those without irAEs. Steroid treatment resulted in a decrease in autoAbs. A prospective study is ongoing to validate the potential role of autoAbs for risk stratification and monitoring of irAEs. [Table: see text]

External validation of the VIGex gene-expression signature (GES) as a novel predictive biomarker for immune checkpoint treatment (ICT)

2510

Background: VIGex is a 12- gene GES classifier initially developed on the Nanostring platform and validated for RNA-seq. VIGex classifies samples into Hot, intermediate-Cold (I-Cold) and Cold subgroups. The Hot subgroup as defined by VIGex has been associated with better (PFS) in patients (pts) treated on phase 1 ICT trials at Vall D’Hebron Hospital (VH) (ESMO2020). We investigated the performance of VIGex in pts treated with Pembrolizumab (P) in the INSPIRE clinical trial (NCT02644369) at Princess Margaret Cancer Centre (PM) and compared VIGex with other predictive ICT biomarkers. Methods: Pts with advanced solid tumors were treated with P 200 mg IV Q3wks. RNA-seq from baseline biopsies was performed using the Illumina NextSeq550 platform. Tumor RNA-seq data were transferred from PM to VH and classified by the VIGex algorithm blinded to clinical data. Bespoke circulating tumor DNA (ctDNA) was assayed at baseline (B) and start of cycle 3 (C3) using a pt-specific amplicon-based NGS assay (Signatera). Tumor mutational burden (TMB) was defined as the number of non-synonymous mutations per megabase and PD-L1 was assessed by immunohistochemistry (22C3). Hot subgroup (HOT) was compared to I-Cold + Cold (COLD). We defined 4 groups based on the combination of VIGex subgroups and the change in ctDNA at cycle 3 from baseline (ΔctDNA). Survival times were calculated with the Kaplan–Meier method and Cox proportional-hazard models were constructed. Results: Out of 76 pts, median age was 55y (range 21-81y), M:F 31:45, all ECOG 0-1, 16 High-grade serous ovarian, 12 triple negative breast, 12 head and neck, 10 melanoma and 26 other. Median no. of P cycles was 3 (range 1–35); follow up was 14m (range 1-67); Median PFS 10.9m and median overall survival (OS) 14m. Overall response rate (RECIST 1.1) was 24% in HOT and 10% in COLD (p = 0.22 two-sided Fisher's exact test). The HOT subgroup was significantly associated with higher OS and PFS when included in a multivariate model adjusted by tumor histology, TMB and PD-L1 (HR 0.43; 95%CI 0.23-0.81; p = 0.009) and (HR: 0.48; 95%CI 0.25-0.95; p = 0.036) respectively. A total of 57 pts had both VIGex and ΔctDNA data. The addition of ΔctDNA further improved the predictive performance of VIGex for OS (Table). Conclusions: VIGex maintained its predictive power for ICT outcomes when applied to an independent external dataset using RNA-seq. The predictive information provided by VIGex was independent of PD-L1 and TMB. Our data indicates that the addition of ΔctDNA to baseline VIGex may refine prediction for ICT outcomes. [Table: see text]

Identification of response stratification factors from pooled efficacy analyses of afamitresgene autoleucel (“Afami-cel” [Formerly ADP-A2M4]) in metastatic synovial sarcoma and myxoid/round cell liposarcoma phase 1 and phase 2 trials

11562

Background: Afami-cel is an autologous, HLA-A*02-restricted, specific peptide enhanced affinity receptor, T-cell therapy engineered to target MAGE-A4+ solid tumors. The pivotal, 2-cohort, single-arm, Phase 2, SPEARHEAD-1 trial (NCT04044768) with afami-cel met its primary endpoint based on Cohort 1 data. As of September 1, 2021, in 47 patients (pts) with metastatic synovial sarcoma (SyS) or myxoid/round cell liposarcoma (MRCLS), the overall response rate (ORR) per independent review was 34% with encouraging durability (Van Tine, et al. Paper 30: CTOS 2021; Virtual). To identify potential stratification factors for response and assess whether response is a proxy for progression-free survival (PFS), we present pooled analyses using data from the prior Phase 1 trial (NCT03132922) and Cohort 1 of the SPEARHEAD-1 trial. Methods: Eligible pts (16–75 years) were HLA-A*02+ with MAGE-A4+ tumors. Pts received afami-cel after lymphodepleting chemotherapy. The pooled analyses evaluated ORR per RECIST v1.1 by investigator review, stratified by 7 factors, and safety. Results: In the pooled data, 69 pts received afami-cel (2.12–9.99×109 transduced T-cells) and were evaluable for response (Phase 1, n = 18; Phase 2, n = 51); all expressed one eligible HLA-A*02 allele. Median (range) for: age was 42 years (19–76), number of prior lines of therapy was 2 (1–12), and tumor MAGE-A4 H-score was 230 (60–300). Median (range) H-score was higher in SyS (256 [60–300]) than in MRCLS (180 [112–230]). The pooled investigator-assessed ORR was 36.2% (40.7% in SyS; 10.0% in MRCLS). Responses occurred across a wide MAGE-A4 H-score range (134–300). Median (range) duration of response was 52 weeks (8.29–75.14). Response rate was higher in the 59 pts with SyS: with ≤2 vs ≥3 prior lines of therapy (55.2% vs 26.7%), baseline target lesion sum of longest diameters <10cm vs ≥10cm (53.1% vs 25.9%), MAGE-A4 H-score ≥200 vs <200 (46.3% vs 27.8%), without vs with bridging therapy (48.6% vs 29.2%), who were female vs male (46.4% vs 35.5%), aged ≥40 vs <40 years (45.7% vs 33.3%), and from North America vs Europe (42.6% vs 33.3%). In responders vs non-responders with SyS, respectively, median PFS was 58.3 vs 11. 0 weeks (log-rank p-value <0.0001); the probability of being progression-free at 24 weeks was 0.8 vs 0.2. The pooled benefit:risk profile of afami-cel was similar to that in the SPEARHEAD-1 trial (Van Tine, et al. Paper 30: CTOS 2021; Virtual.). Conclusions: We show that baseline tumor burden, prior systemic treatment history, and MAGE-A4 tumor expression levels are potential factors associated with response to afami-cel, although their true predictive value for response status awaits confirmation. Our findings will inform the ongoing clinical development of afami-cel in sarcoma, especially for prognostic studies with PFS or overall survival endpoints. Clinical trial information: NCT04044768, NCT03132922.

Methylated circulating tumor DNA (cfMeDIP) as a predictive biomarker of clinical outcome in pan-cancer patients (pts) treated with pembrolizumab (P)

2550

Background: Bespoke mutation-based circulating tumor DNA (ctDNA) predicts response to P but relies on availability of tumor tissue and presence of mutations. Cell-free methylated immunoprecipitation and high-throughput sequencing (cfMeDIP-seq) may overcome these limitations and be applied to more pts. Methods: Pts with mixed solid tumors divided into 5 cohorts received P 200 mg Q3wks in the investigator-initiated INSPIRE trial (NCT02644369). cfMeDIP-seq was performed at baseline (B), pre cycle 3 (C3) and later cycles. Methylation probability was inferred from read depths in 300 bp bins. cfMeDIP score was the probability-weighted sum of 3270 pan-cancer differentially-methylated regions in the TCGA PanCanAtlas. ctDNA concentration was assayed using tissue-informed bespoke targeted NGS (Signatera). ΔctDNA and ΔcfMeDIP denote the change in ctDNA or cfMeDIP between B and C3, respectively. Association with OS or PFS was assessed using Cox proportional hazards model, adjusting for cohort (aHR). Multivariable analysis (MVA) also included tumor mutation burden and PD-L1 status. Results: 194 plasma samples from 87 pts were analysed with cfMeDIP-seq (84 at B, 55 at C3, 55 at later cycles). Demographics: male 33%; median age = 61 yrs (34–82); Cohorts: triple negative breast (26%), ovarian (25%), head & neck (21%), melanoma (12%), others (15%). Median follow-up = 10.6m (0.6–64.4); Median PFS = 1.9m; Median OS = 10.6m. cfMeDIP at B below median was associated with better OS (aHR = 0.51, 95%CI 0.29-0.91; p = 0.02) in MVA. ΔcfMeDIP was evaluable in 53 pts; any decrease in ΔcfMeDIP was predictive for OS (aHR = 0.36, 95%CI 0.18-0.72; p < 0.01) and PFS (aHR = 0.42, 95%CI 0.22-0.82; p = 0.01). Both ΔctDNA and ΔcfMeDIP were evaluable in 51 pts; decrease in ΔctDNA and ΔcfMeDIP predicted for longer OS (aHR = 0.45, 95%CI 0.23-0.86; p = 0.02 vs aHR = 0.39, 95%CI 0.19-0.80; p = 0.01); and PFS (aHR = 0.44, 95%CI 0.23-0.83; p = 0.01 vs aHR = 0.5, 95%CI 0.25-0.99; p = 0.04), respectively. When both ΔctDNA and ΔcfMeDIP are integrated in MVA, ΔcfMeDIP was predictive for OS (aHR = 0.48, 95%CI 0.23-1; p = 0.05). A decrease in ΔcfMeDIP and/or ΔctDNA was associated with longer OS (aHR = 0.2, 95%CI 0.09-0.45) and PFS (aHR = 0.27, 95%CI 0.13-0.58) compared to an increase in both assays (p < 0.01) (Table). Conclusions: We applied for the first time cfMeDIP-seq and mutation-based ctDNA analysis concurrently in pan-cancer pts treated with checkpoint blockade. ΔcfMeDIP correlated strongly with OS and PFS, representing a promising plasma-based predictive epigenetic biomarker in pts treated with P. ΔctDNA and ΔcfMeDIP can complement each other to predict outcomes, demonstrating that they may capture different biological changes. Clinical trial information: NCT02644369. [Table: see text]

Phase 1b study of weekly split-dose selinexor in soft tissue sarcoma (STS)

11563

Background: Selinexor has demonstrated clinical activity in a variety of tumors including STS. Selinexor dosing at 60mg twice a week or 80mg once a week in later phase trials was associated with gastrointestinal and hematologic toxicities requiring frequent dose interruption and reduction. Preclinical in vivo studies show that selinexor use in a split-dose regimen or sustained-release formula is associated with less toxicity. This phase 1b study aimed to evaluate the safety and tolerability of split-dose selinexor in patients (pts) with advanced STS. Methods: Eligible pts with advanced STS of any histologic subtype, and ECOG performance status (PS) ≤ 1 were treated with split-dose selinexor (40mg, 20mg, 20mg in the morning, afternoon, and evening, respectively) on days 1, 8, 15 and 22 of a 28-day cycle, until unacceptable toxicity or disease progression. Antiemetic prophylaxis (oral dexamethasone and ondansetron) was given to all pts. The primary endpoint was the rate of grade ≥ 3 treatment-related adverse events (TRAE) by CTCAE v5.0. The secondary endpoint was assessment of quality of life (QoL) using the EORTC QLQ-c30 tool v3. Descriptive analyses of Global Health Status (GHS) QoL scores at screening (baseline) and cycle 2 day 1 (C2D1) were performed. Radiologic tumor assessments (by RECIST v1.1) were performed every 8 weeks while on treatment. Results: Nineteen pts [12 female and 7 male; ECOG 0/1, 8/11; median age 61 years (range 41 – 83)] were enrolled. The most frequent of 12 STS subtypes was leiomyosarcoma (n = 7, 37%). Among 18 patients evaluable for toxicity, there were no grade ≥ 3 TRAE. The most common grade ≤ 2 TRAE were dysgeusia (n = 11, 61%), nausea (n = 11, 61%), fatigue (n = 10, 56%) and vomiting (n = 10, 56%). Grade ≤ 2 hematologic TRAE were thrombocytopenia (n = 6, 33%), neutropenia (n = 4, 22%) and anemia (n = 1, 6%). Dose reduction was required in 3 pts (17%) due to intolerable grade 2 TRAE (fatigue, nausea, thrombocytopenia). No serious adverse event due to selinexor was noted. QoL scores were evaluable for 15 pts. The mean (± SEM) change in GHS QoL score from baseline to C2D1 was -10.6 (± 4.8). Among 16 pts evaluable for radiologic response, the best response was stable disease (SD) in 10 pts (63%), and progressive disease (PD) in 6 pts (37%). Durable clinical benefit (SD for > 16 weeks) was seen in 5 pts (31%; 95%CI 11.0 – 58.7%) The median PFS was 3.6 months (95%CI 1.7 – 7.3). Conclusions: Split-dose selinexor was well tolerated in this heterogeneous group of pts with advanced STS and warrants further interrogation. Updated toxicity, safety, efficacy and QoL data will be presented at the meeting. Clinical trial information: NCT04811196.

Real-world experience of tyrosine kinase inhibitors in patients (pt) with recurrent bone tumours (BT): A CanSaRCC study

11530

Background: Survival after relapse in osteosarcoma (OST), Ewing Sarcoma (ES) and chondrosarcoma (CS) remains dismal. Recent reports suggest a role of tyrosine kinase inhibitors (TKI) including regorafenib (R) and cabozantinib (C). We conducted a retrospective multi-centre pan-Canadian study to assess real-word outcomes with these novel treatments in recurrent BT. Methods: After ethics approval, data from pts treated in 7 different institutions was extracted from the CanSaRCC (Canadian Sarcoma Research and Clinical Collaboration) Database. Pt characteristics, treatment and outcomes were analyzed. Response was assessed per RECIST 1.1. PFS, OS were estimated using Kaplan-Meier. TTP was defined as time from TKI start to progression. Results: From June 2018-Dec 2021, 44 pts received R or C and best response by histology are listed in Table, with an overall clinical benefit rate of 63.6%. Median time to best response was 2.3 mo (range 1 – 17). 15 pts (34.1%) required dose reduction; most common reasons were hand-foot syndrome (13.6%), mucositis (9.1%) and hypertension (9.1%). At median FU of 6.4 mo (range 1.6 – 29), 25 pts (56.8%) died, 19 (43.2%) were alive with disease (AWD). Median PFS was 4.1 mo (95%CI 2.9 – 5.7), for OST was 5.0 (N = 25, 95%CI 2.6 – 10.6), for ES was 4.1 (N = 10, 95%CI 2-5.9), and for CS 4.0 (N = 9, 1 Progressed). Median OS was 10.5 mo (95%CI 7 – 14). By univariate analysis, age, line of therapy, gender, location of primary, or R vs. C did not correlate with PFS. Conclusions: Consistent with previous published studies, our pan-country real-world analysis shows that TKI have meaningful activity in the setting of recurrent BT with acceptable toxicities. Inclusion in earlier lines of treatment and/or maintenance therapy could be questions for future research. [Table: see text]

A phase 2 study of anti-PD-L1 antibody (atezolizumab) in grade 2 and 3 chondrosarcoma

11528

Background: Chondrosarcoma is one of the most common bone malignancies in adults, and the third most common in pediatric patients (pts). The most prevalent subtype, conventional chondrosarcoma, is a slow growing tumor that is historically known to be refractory to chemotherapy. Anecdotal reports indicated a role for anti-PD-(L)1 in the treatment of this disease. This is the first prospective report on the efficacy of the PD-L1-targeting agent, atezolizumab, in this rare disease. Methods: Patients (pts) ages 2 and older with unresectable grade 2 or 3 conventional chondrosarcoma were eligible. No prior anti-PD-(L)1 treatment was allowed, otherwise pts were eligible irrespective of prior therapies as long as protocol-specified washout period requirements were met. Pts received atezolizumab 1200 mg (15 mg/kg with 1200 mg cap in pediatric pts) once every 21 days. Imaging was carried out at end of cycle 3, and then every two cycles. Research biopsies were collected from adult pts prior to C1D1, prior to C3D1, and at progression. Immuno-pharmacodynamic (IO-PD) studies were performed on paired tumor samples and circulating immune cells to help elucidate signaling pathways mediating the immune response, with focus on subsets of effector cells in the tumor microenvironment. Results: A total of 9 pts (7 males, 2 females) were enrolled in 6 centers across the US and Canada. Six pts were Caucasian/White, 1 Asian, 1 Hispanic, and 1 unknown. Median age was 49 years (42-72). No objective responses were seen. Three pts (33%) experienced disease stability (SD) per RECIST 1.1, for a median duration of 21 weeks as of data cutoff (January 2022). A patient with SD remains on active treatment (tx) for 35 weeks. Three patients had no tx-related adverse events (AEs). Six pts (67%) experienced at least one tx-related AE. Two patients experienced > G2 AEs, but only one was considered tx-related (lymphopenia). Immune-related AEs were all G1/2 and included hepatitis (2), hypothyroidism (1), hyperthyroidism (1), and maculopapular rash (1). IO-PD studies are ongoing and will be reported at the conference if available. Conclusions: Atezolizumab was well-tolerated but demonstrated limited activity in this cohort of pts with few treatment options. Ongoing IO-PD studies will provide insight into atezolizumab’s effect upon immune cell content and activation in the tumor microenvironment that will help design future immunotherapy trials in this disease and other sarcoma types. The study was funded by NCI Contract HHSN261201500003I. Clinical trial information: NCT04458922.

The effect of circadian rhythm on clinical outcome in patients receiving pembrolizumab in the INSPIRE pan-cancer trial

2589

Background: The molecular networks comprising circadian rhythm are expressed in immune cells where they affect immune-related processes. Within the emerging field of chrono-immunotherapy, it has been proposed that immunotherapies should be applied at certain times of day to optimize efficacy. Two recent reports have suggested that earlier administration of immune checkpoint inhibitors (ICIs) in non-small cell lung cancer and melanoma may offer improved survival outcomes (Karaboué et al. ASCO 2021, PMID 34780711). Whether this observation applies to other tumour types, or occurs in geographic regions with differing seasonality, is not known. Methods: We retrospectively analyzed the time of administration data from the INSPIRE single-centre, phase II, multi-cohort study of pembrolizumab (200 mg IV over 1 hour, q3w to maximum 35 cycles) in patients with advanced solid tumours (NCT02644369). Kaplan-Meier methods were used to estimate PFS and OS. Cox proportional hazards models were fitted to assess the association between time of administration and PFS or OS, adjusting for cohort. Fisher’s exact test was used to test for association with immune-related adverse events (irAEs). Results: A total of 106 patients (19 head and neck squamous cell, 22 triple negative breast, 21 epithelial ovarian, 12 melanoma, 32 other solid tumours) were accrued between March 21, 2016, and May 9, 2018. Median time of follow-up was 11.5 months. Start of infusion times were obtained for 806 total doses. The median time of administration was 15h06 for the first dose and 15h11 for all doses (range 09h19 – 18h34). No differences in PFS or OS were observed between patients who received their first dose before or after noon, or before or after 15h06. Furthermore, no differences in PFS or OS were observed between patients who received ≥ 50% of their doses before or after noon, or before or after 15h11. There was also no difference in PFS or OS between patients who did or did not have a significant proportion of doses (≥ 20%) after 16h30 (“evening” in previous reports). There were no differences in the frequency of grade ≥ 2 irAEs amongst the various groups. No differences in efficacy were found when individual cohorts were evaluated separately. Finally, no differences in PFS or OS were observed when participants were grouped by season of first dose. Conclusions: Despite previous reports of improved survival with earlier ICI dosing, we did not identify any association of time of pembrolizumab administration with clinical outcomes. Our analysis is limited by small sample size and patient heterogeneity which may hinder identification of smaller associations. It is also unclear whether lower response rates in a pan-cancer population (relative to prior reports in lung cancer and melanoma) might impact correlation analysis. Further studies will be necessary to interrogate this phenomenon and ensure that ICI are optimally applied.

INT230-6 monotherapy and in combination with ipilimumab (IPI) across a broad spectrum of refractory soft tissue sarcomas (STS) [Intensity IT-01; BMS#CA184-592]

11515

Background: INT230-6 is a novel intratumoral (IT) agent with a dual anti-cancer mechanism (tumor cytoreduction while stimulating antigen presentation and recruitment of T-cells). The drug is comprised of cisplatin (CIS) and vinblastine (VIN) co-formulated with an amphiphilic molecule that enables drug dispersion throughout tumors and passive diffusion into cancer cells following IT delivery. In the neoadjuvant setting, a single injection can cause necrosis in > 95% of the tumor and recruit TILs. Combining with anti-CTLA-4 improved responses in preclinical models. Methods: INT230-6 dose is set by the tumor’s longest diameter and is proportional to the injected disease volume. INT230-6 is administered IT Q2W for 5 treatment sessions followed by maintenance every 9 weeks as monotherapy or with IPI 3mg/kg IV Q3W for 4 doses. Biopsies from injected tumors are obtained pretreatment and Day 28 for immunoprofiling. Results: 22 subjects with various advanced STS histologies with a median age of 64 and a median of 3 prior systemic therapies were enrolled (11 INT230-6 alone, 11 IPI combination). There were 178 image-guided IT INT230-6 injections (107 to deep tumors) at INT230-6 doses ranging from 5 to 242 mL (121mg CIS, 24.2mg VIN, doses which vastly exceed the usual IV doses of these drugs). PK analysis showed that > 95% of drug agents remain in the tumor. The most common (> 25%) all-grade related adverse events (AEs) in evaluable monotherapy subjects (n = 10) were pain (80%), decreased appetite (40%), nausea (40%), anemia (30%), fatigue (30%) and vomiting (30%). Tolerability was similar for the combination with IPI. Most events were low grade. The incidence of grade 3 AEs for the INT230-6 arm was 30% and for the IPI combination was 10%. There were no related grade 4 or 5 AEs in either cohort. RECIST metrics may not accurately reflect clinical benefit with this treatment given large volumes of INT230-6 is repeatedly injected into a tumor and local inflammation may occur. Paired biopsies showed reduction in proliferating tumor cells and an increase in T-cell infiltrates. The disease control rate at the first imaging timepoint for evaluable INT230-6 subjects (n = 9) was 56% and for evaluable IPI combination (n = 5) was 80%. Abscopal effects were seen in 2 monotherapy subjects, though most uninjected tumors were not tracked. The estimated 1-year overall survival was 88% for the IPI combo and 60% for the monotherapy cohort. Conclusions: IT INT230-6 is well tolerated as monotherapy and combined with IPI. STS, which is typically not sensitive to immunotherapy, may be amenable to INT230-6 or IPI combo to create antigens and promote a systemic immune response. Preliminary efficacy using INT230-6 alone is encouraging and will be evaluated in a global phase 3 trial. Further evaluation is needed to determine whether the addition of IPI may improve patient outcomes. Clinical trial information: NCT03058289.

Synergistic activity of PARP inhibitors (PARPi) in combination with standard chemotherapy (CTx) in leiomyosarcoma

11560

Background: Leiomyosarcomas (LMS) are genetically heterogeneous tumors that arise from smooth muscle. Currently, the mainstay of systemic treatment for patients with advanced/metastatic disease is doxorubicin (Dox) based CTx. Several genomic analyses of LMS reveal defects in homologous recombination (HR) DNA repair pathway in about half of patients, consistent with a druggable “BRCAness” phenotype. Thus, we sought to determine which combinations of standard CTx and PARPi might be synergistic promising therapeutic strategies for LMS. Methods: Dox, Docetaxel (Doc), Temozolomide (Tmz) were evaluated in combination with PARPi (Olaparib [Ola], Niraparib [Nira] and Talazoparib [Tala]) at 12 different drug concentrations. Four LMS cell lines of different origins (gynecological - GY, abdominal - A, extremity - E) were tested in a high throughput manner. All drug concentrations were chosen according to EC50. Cells were incubated with each combination for 7 days. Viability was assessed by ATPlite Luminescence Assay System.Evaluation of drug combination effect was performed using a Bliss synergy score. This system quantifies the degree of synergy as multiplicative effect of single drugs as if they acted independently. With a synergy score of -5 to 5, the interaction between two drugs is considered as additive; <-5 antagonistic and > 5 synergistic, and therefore a promising combination. Results: Anticancer activity, ranging from additive to synergistic was seen with all combinations. Results were consistent among all cell lines, independent of site of cell line origin (Table) Most synergistic combination in the majority of LMS cell lines were Dox or Tmz when combined with Tala, reaching up to 15 % and 27% above Bliss respectively. In contrast, Doc showed only additive effect with all analyzed PARPi. Conclusions: The data suggest that the combination of Dox or Tmz with PARPi may represent promising treatment options for LMS patients. Recent clinical studies support this notion in uterine LMS. Importantly these results suggest that such approach may be extended to all sites of LMS. Pre-clinical studies are underway to identify the most promising combinations for future clinical trial design. [Table: see text]

INTRIGUE: A phase III, randomized, open-label study to evaluate the efficacy and safety of ripretinib versus sunitinib in patients with advanced gastrointestinal stromal tumor previously treated with imatinib

359881

Background: Sunitinib is approved for advanced gastrointestinal stromal tumor (GIST) after imatinib failure. Ripretinib, a broad-spectrum KIT and PDGFRA switch-control tyrosine kinase inhibitor (TKI), is indicated for the treatment of adult patients (pts) with GIST who received prior treatment with 3 or more TKIs, including imatinib. We compared the efficacy and safety of ripretinib vs sunitinib in pts with advanced GIST who progressed on or were intolerant to imatinib. Methods: This multicenter, global, randomized, open-label phase 3 study (NCT03673501) enrolled adult pts with GIST who progressed on or had intolerance to imatinib. Pts were randomized 1:1 to ripretinib 150 mg once daily (QD) or sunitinib 50 mg QD (4 wks on/2 wks off). Randomization was stratified by KIT mutational status and imatinib intolerance. The primary endpoint was progression-free survival (PFS) by independent radiologic review (IRR) using modified RECIST version 1.1. Key secondary endpoints were objective response rate (ORR) by IRR and overall survival (OS). Hierarchical testing was performed for primary and key secondary endpoints in a prespecified sequence; testing pts with a KIT exon 11 primary mutation (Ex11 intention-to-treat [ITT] population) preceded the all-patient (AP) ITT population. Data cutoff was 1 Sep 2021; final analyses of PFS and ORR and the first interim analysis of OS were conducted. Results: A total of 453 pts were randomized to ripretinib (n = 226; Ex11 ITT, n = 163) or sunitinib (n = 227; Ex11 ITT, n = 164). Median age was 60 yrs (range 18–88) and most pts were white (66.2%) males (62.0%). PFS was not statistically different between ripretinib and sunitinib in the Ex11 ITT (hazard ratio [HR] 0.88, 95% CI 0.66, 1.16; P = 0.36; median 8.3 vs 7.0 mos) or in the AP populations (HR 1.05, 95% CI 0.82, 1.33; P = 0.72; median 8.0 vs 8.3 mos). ORR was numerically higher for ripretinib vs sunitinib in the Ex11 ITT (23.9% vs 14.6%; difference 9.3%, 95% CI 0.7, 17.8; nominal P = 0.03) and AP ITT populations (21.7% vs 17.6%; difference 4.2%, 95% CI −3.2, 11.5; nominal P = 0.27). OS data was highly immature; median OS was not reached in either arm. Fewer pts in the ripretinib arm experienced Grade 3-4 (G3-4) treatment-emergent adverse events (TEAEs) vs sunitinib (41.3% vs 65.6%). Among G3-4 TEAEs with a difference ≥5% between arms, ripretinib had fewer events vs sunitinib (hypertension [8.5% vs 26.7%], palmar-plantar erythrodysesthesia [1.3% vs 10.0%], neutropenia [0% vs 6.3%], and neutrophil count decreased [0% vs 7.2%]). Conclusions: The PFS in both arms was longer than PFS achieved by sunitinib in its pivotal phase 3 trial. While the PFS for ripretinib did not meet the primary endpoint of superiority vs sunitinib, meaningful clinical activity and fewer G3-4 TEAEs were observed in pts with advanced GIST treated with ripretinib after imatinib failure. Clinical trial information: NCT03673501.

Epithelioid hemangioendothelioma, an ultra-rare cancer: a consensus paper from the community of experts

Epithelioid hemangioendothelioma (EHE) is an ultra-rare, translocated, vascular sarcoma. EHE clinical behavior is variable, ranging from that of a low-grade malignancy to that of a high-grade sarcoma and it is marked by a high propensity for systemic involvement. No active systemic agents are currently approved specifically for EHE, which is typically refractory to the antitumor drugs used in sarcomas. The degree of uncertainty in selecting the most appropriate therapy for EHE patients and the lack of guidelines on the clinical management of the disease make the adoption of new treatments inconsistent across the world, resulting in suboptimal outcomes for many EHE patients. To address the shortcoming, a global consensus meeting was organized in December 2020 under the umbrella of the European Society for Medical Oncology (ESMO) involving >80 experts from several disciplines from Europe, North America and Asia, together with a patient representative from the EHE Group, a global, disease-specific patient advocacy group, and Sarcoma Patient EuroNet (SPAEN). The meeting was aimed at defining, by consensus, evidence-based best practices for the optimal approach to primary and metastatic EHE. The consensus achieved during that meeting is the subject of the present publication.

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This consensus paper provides key recommendations on the management of epithelioid hemangioendothelioma (EHE).

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Recommendations followed a consensus meeting between experts and a representative of the EHE advocacy group and SPAEN.

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Authorship includes a multidisciplinary group of experts from different institutions from Europe, North America and Asia.

The impact of multimodality therapies in marginally inoperable soft tissue sarcomas (STS): The Toronto Sarcoma Program (TSP) experience

11548

Background: The mainstay therapy of operable STS remains surgery, which may include (neo)adjuvant therapies. Within the TSP, marginally inoperable STS are often treated with sequential chemo (CTX) and radiation (RT) therapy, followed by surgery (SX). Herein we present our experience of multi-modality therapies for marginally inoperable STS patients (pts). Methods: This was a dual-center, single program, retrospective review. Pts were included if deemed to have marginally inoperable primary or recurrent STS, as determined at the TSP tumor board. Pts included must have had CTX with the intent of having RT and SX after. Pts demographics, treatment details and clinical outcomes data were collected. Relapse free survival (RFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Multivariate analysis of the influence of disease characteristics and treatment on outcomes was assessed using Cox regression. Results: From June 2005 to May 2019, 75 pts were identified. Median age was 52 years (range 16-72). Pts were predominantly male (55%). Histological subtypes included dedifferentiated liposarcoma (29%), leiomyosarcoma (27%), synovial sarcoma (19%) and others (25%). Primary tumor was located in the retroperitoneum (48%), extremity (23%), pelvis (12%), thorax (9%), and other sites (8%). All pts had doxorubicin and ifosfamide CTX (median 4 cycles; range 1-6), while RT dose delivered was 50.4Gy/28 fractions in 58 (77%) of cases. Twenty three pts (31%) achieved partial response, 40 pts (53%) had stable disease and 12 pts (16%) had progression of disease (PD) on CTX, of which half (8%) did not undergo further treatment. Nine pts (12%) underwent CTX followed by SX due to significant response, 9 pts (12%) underwent CTX and RT without SX due to persistent tumor unresectability or PD. The final 50 pts (67%) completed multi-modality treatment (CTX, RT & SX). Overall, 59 pts (79%) had SX; negative margins were achieved in 53 (71%). 19 pts (25%) had postoperative complications, causing death in 2 pts (2.7%). With a median follow-up of 72 months, median RFS and OS were 26.9 months (95% CI: 0-86.0), and 65 months (95% CI: 13.5-116.4). Extremity location was associated with superior RFS (median not reached [NR], HR 0.28 95% CI 0.09-0.83, p = 0.022), and OS (median NR, HR 0.29 95% CI 0.09-0.90, p = 0.032). Receipt of RT was associated with superior RFS (median NR, HR 0.23 95% CI 0.10-0.52, p < 0.001); and OS (median NR, HR 0.21 95% CI 0.09-0.50, p < 0.001). Pts who had PD after CTX were associated with poor outcomes - RFS (median 4.7 months, HR 2.03 95% CI 0.61-6.76, p = 0.24); and OS (median 21.9 months, HR 2.48 95% CI 0.73-8.47, P = 0.144). Conclusions: Multi-modality approach resulted in successful resection for most pts with marginally inoperable STS. Extremity location and RT administration were associated with better RFS and OS, while progression on CTX confers worse survival outcomes.

Immune Resistance Interrogation Study (IRIS): A prospective comprehensive multi-omic analysis in patients with intrinsic and acquired resistance to immunotherapy

TPS2679

Background: Immune checkpoint inhibitors (ICI) have demonstrated efficacy in a wide variety of cancers. Nevertheless, only a small proportion of patients derive a durable benefit. Mechanisms underlying primary and acquired resistance are still incompletely understood. They comprise tumor-intrinsic factors such as genomic and transcriptomic changes; upregulation of immunosuppressive subsets; T cell exhaustion; and promotion of an immune-tolerant tumor microenvironment. The collection of tumor biopsy at disease progression (PD) is challenging both in clinical and research settings as this often occurs at the time of treatment discontinuation. However, the analysis of these samples can lead to novel strategies to prevent or reverse immune resistance. Thus, the current approach to begin a profiling study with patients at the time of PD on ICI enables access and interrogation of such samples. Methods: IRIS is a prospective, investigator-initiated trial at the Princess Margaret Cancer Centre that aims to extensively characterize the genomic, transcriptomic, epigenetic and immunophenotypic profiles of tumors with primary versus acquired resistance to ICI-based therapy. Primary resistance is defined as PD at the first on-treatment imaging, whereas acquired resistance is defined as PD occurring after an initial partial or complete response or following disease stability lasting ≥6 months. Additional objectives include the evaluation of radiomic parameters on standard radiological imaging, investigation of fecal microbiome, generation of patient-derived organoids and facilitation of data and sample sharing with the research community. The planned samples size is 100 patients. A one-time fresh tumor biopsy, blood and stool samples and archival tissue (when available) are collected at the time of PD on ICI (baseline) from all the participants. Longitudinal blood samples are obtained every 2-3 months (around the time of tumor imaging) until PD in patients receiving a subsequent treatment. Subjects who are not amenable for therapy undergo blood collections at the time of further PD. Molecular characterization of tumor samples includes: DNA/RNA sequencing, Assay of Transposase Accessible Chromatin (ATAC)-sequencing, Cellular Indexing of Transcriptomes and Epitopes (CITE)-sequencing, multiplexed immunohistochemistry and flow cytometry. Results of NGS performed on the first biopsy core are returned to patient and physician. Key eligibility criteria include diagnosis of solid tumor, progression to ICI as the most recent line of treatment and disease amenable to core needle biopsy. The IRIS trial, activated in October 2020, is currently open to enrollment. As of January 2021, 21 patients have been enrolled and a total of 92 tissue cores, 42 blood and 20 stool samples have been collected. Clinical trial information: NCT04243720.

IGNYTE-ESO: A master protocol to assess safety and activity of letetresgene autoleucel (lete-cel; GSK3377794) in HLA-A*02+ patients with synovial sarcoma or myxoid/round cell liposarcoma (Substudies 1 and 2)

TPS11582

Background: Letetresgene autoleucel (lete-cel; GSK3377794) is an autologous T-cell product using a genetically modified T-cell receptor to target cancer cells expressing the cancer testis antigen New-York esophageal squamous cell carcinoma 1 (NY-ESO-1). Lete-cel is currently being investigated alone and in combination in multiple tumor types [1,2]. NY-ESO-1 is expressed in 70‒80% of synovial sarcoma (SS) and 80‒90% of myxoid/round cell liposarcoma (MRCLS) tumors [3,4], suggesting these tumors may be prime lete-cel targets. This master protocol design (IGNYTE-ESO; NCT03967223) enables evaluation of multiple cell therapies in multiple tumor types and treatment stages in separate substudies, beginning with lete-cel in Substudies 1 and 2 for SS and MRCLS. Methods: Substudy 1 is a single-arm study assessing lete-cel in treatment-naïve patients (pts; ie, anthracycline therapy-naïve for metastatic disease) with advanced (metastatic/unresectable) NY-ESO-1+ SS or MRCLS as a first line of therapy (n=10 planned). Substudy 2 is a pivotal, single-arm study assessing lete-cel in pts with NY-ESO-1+ SS or MRCLS who progressed after anthracycline therapy (n=70 planned). Key eligibility criteria are age ≥10 y and NY-ESO-1 and HLA-A*02 positivity. Exclusion criteria include prior NY-ESO-1–specific/gene therapy, allogeneic stem cell transplant, and central nervous system metastases. Screened pts undergo leukapheresis for lete-cel manufacture, lymphodepletion, lete-cel infusion, and follow-up (FU). Long-term FU (15 y) may be done under a separate protocol. The Substudy 2 primary endpoint is overall response rate (ORR) per RECIST v1.1 assessed by central independent review. Substudy 1 is not testing any formal hypotheses; statistical analysis will be descriptive. Substudy 2 is comparing ORR with the historical control assuming at least 90% power with 0.025 one-sided type I error. Secondary endpoints include efficacy (time to/duration of response, disease control rate, progression-free survival), safety (adverse event [AE] frequency/severity, serious AEs, AEs of special interest), and pharmacokinetic (maximum transgene expansion [Cmax], time to Cmax, area under the time curve from zero to time t as data permit). Enrollment began in December 2019. References: 1. Reckamp KL, et al. Ann Oncol 2019;30(Suppl_5):v602–v660. 2. Rapoport A, et al. J Clin Oncol 2020 38:15_suppl, TPS8555. 3. D’Angelo SP, et al. Cancer Discov 2018;8(8):944–957. 4. D’Angelo SP, et al. J Clin Oncol 2018 36:15_suppl, 3005. Funding: GSK. Editorial support was provided by Eithne Maguire, PhD, of Fishawack Indicia, part of Fishawack Health, and funded by GSK. Previously presented at BSG 2021 (P914542). Clinical trial information: NCT03967223.

ESMO Magnitude of Clinical Benefit Scale (MCBS): An evaluation of systemic treatment trials for soft tissue sarcomas (STS)

11553

Background: Patients with STS have poor prognosis in the metastatic setting. Although some treatment options are associated with improved outcomes, such as progression-free (PFS) or overall survival (OS), the overall magnitude of clinical benefit can be unclear. The ESMO MCBS is a validated and reproducible tool developed to quantify the clinical benefit of treatments evaluated in trials ( www.esmo.org/guidelines/esmo-mcbs ). Herein, we report the application of ESMO MCBS to systemic treatment trials involving metastatic STS patients. Methods: A systematic search of Medline, Embase and Cochrane databases for adult phase II and III trials in advanced STS (01/1998 to 12/2020) was carried out. Gastrointestinal stromal tumor trials were excluded. Outcomes, including but not limited to OS, PFS, objective response rate (ORR), toxicity and quality of life (QoL) data were extracted and analyzed. Studies with outcomes that met the criteria for ESMO MCBS v1.1 were evaluated to generate a score of 1 to 5 (score of ≥ 4: substantial benefit). MCBS scoring of each study was performed by at least 2 co-authors for consensus. Results: Among 3454 abstracts screened, a total of 140 Phase II and 28 phase IIII trials were identified. A total of 41 studies fulfilled the criteria for ESMO MCBS scoring. These include 5 phase III studies, as well as 9 randomized and 27 single-arm phase II trials. Fifteen studies involved specific histology, while remaining 26 studies were of all STS subtypes. Chemotherapy, alone or in combination was evaluated in 29 trials, while molecular-targeted agents (MTA) and immune checkpoint inhibitors (IO) were evaluated in 11 and 3 studies, respectively (Table). The median MCBS score was 2 (range 1-4), regardless of drug class or combination. Only 3 studies, all randomized in design, had a MCBS score of 4. All three trials were in the 2nd line setting or beyond, where there is no standard control treatment. None of the trials, irrespective of drug class had a score of 5 and no study showed evidence of significant improvement in QoL. The observed MCBS scores were low, partly because the trials evaluated mainly comprise single-arm studies without QoL assessments, restricting to a maximum MCBS score of 3. Conclusions: Most systemic therapy trials in advanced STS did not confer substantial clinical benefit when evaluated using MCBS. Although randomized phase 3 trials remain the gold standard of treatment evaluation, clinical benefit evaluation of STS trials using tools such as MCBS may be useful. Incorporation of QoL evaluation, even in single-arm studies should be prioritized in metastatic STS trials.[Table: see text]

A first-in-human study of mirzotamab clezutoclax as monotherapy and in combination with taxane therapy in relapsed/refractory solid tumors: Dose escalation results

3015

Background: Mirzotamab clezutoclax (ABBV-155) is a first-in-class antibody drug conjugate comprised of a BCL-XL (B-cell lymphoma - extra long) inhibitor, solubilizing linker, and a monoclonal anti-B7H3 antibody. Methods: Patients (pts) with relapsed and/or refractory (R/R) solid tumors were administered mirzotamab clezutoclax with or without paclitaxel. Dose escalation of mirzotamab clezutoclax was guided by Bayesian continual reassessment. Primary outcomes were to determine the maximum tolerated dose (MTD) and the recommended phase 2 dose (RP2D). Secondary outcomes: safety, pharmacokinetics, and overall response rate per RECIST v1.1. Results: As of November 6, 2020, 31 pts received mirzotamab clezutoclax monotherapy (monoTx) and 28 pts received combination therapy with paclitaxel (comboTx). Overall demographics: median age 62 years (range 25–79); 61% female; 86% white; 24% ECOG 0, 76% ECOG 1; 51% had > 3 prior systemic therapies. The median duration of mirzotamab clezutoclax exposure was 3 cycles (range 1–14) for monoTx and 5 cycles (range 1–14) for comboTx. There were no dose limiting toxicities (DLT) reported with monoTx. In comboTx, 2 pts experienced a DLT: Grade 4 neutrophil count decreased and Grade 3 lymphocyte count decreased considered related to paclitaxel. 97% of all pts had adverse events (AEs). The most common AEs (in ≥20% of pts) overall were fatigue (39%), nausea (25%), diarrhea and arthralgia (22% each), vomiting and hypokalemia (20% each). AEs in ≥5 pts related to mirzotamab cleuzutoclax were fatigue (27%), diarrhea (12%), and nausea (9%). Related Grade 3/4 AEs overall (in > 1 patient) included anemia, lymphocyte count decreased, fatigue, and diarrhea (3% each). One patient on monoTx experienced a fatal cardiac arrest. No fatal AEs occurred on comboTx. Responses were observed with comboTx as shown in the Table. Conclusions: Mirzotamab clezutoclax as monotherapy and with paclitaxel demonstrates a tolerable safety profile (MTD not reached) with anti-tumor activity in R/R solid tumors. Further investigation in prospectively-selected B7H3 positive tumors as monoTx in pts with R/R small cell lung cancer and with paclitaxel in pts with R/R breast cancer and docetaxel in pts with R/R non-small cell lung cancer in the dose expansion phase is ongoing. Clinical trial information: NCT03595059. [Table: see text]

Analysis of homologous recombination DNA repair gene mutation status in patients with metastatic small cell lung cancer treated with cediranib and olaparib on NCI 9881 study

8563

Background: Cediranib, a pan-vascular endothelial growth factor receptor tyrosine kinase inhibitor, suppresses expression of homologous recombination DNA repair (HRR) genes and increases sensitivity of tumors to a poly-(ADP-ribose) polymerase (PARP) inhibitor in vitro and in vivo models of breast and ovarian cancer. Olaparib, a PARP inhibitor, demonstrated clinical efficacy in patients with advanced solid tumor with a deleterious mutation in HRR genes. We hypothesized that cediranib induces HRR deficient phenotype by suppressing expression of HRR genes and cediranib and olaparib combination (C+O) results in an objectives response in patients with HRR proficient (HRP) advanced solid tumors. Herein, we report the biomarker data from analyses of targeted sequencing of 84 DNA repair (DR) genes with BROCA-HR assay in patients with metastatic small cell lung cancer (mSCLC). Methods: This multi-institutional phase 2 trial enrolled patients with mSCLC previously treated with a platinum-based chemotherapy. Patients received cediranib 30mg orally (po) daily plus olaparib 200mg po twice daily until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) by RECIST v1.1. A tumor biopsy was obtained from the patients with safely accessible metastatic tumor. HRR deficiency (HRD) was defined as presence of a deleterious mutation in any of the 10 key HRR-related genes per BROCA-HR assay including: ATM, BARD1, BRCA1, BRCA2, BRIP1, CDK12 (somatic mutations only), NBN, PALB2, RAD51C, or RAD51D. Otherwise, the tumors were defined as HRR proficiency (HRP). Results: A total of 25 patients with SCLC received the study treatment. Fourteen patients had available tumor biopsy samples and/or germline available for BROCA-HR. One patient (7%) was determined to have a HRD tumor by a presence of PALB2 mutation. This patient had stable disease as a best overall response but came off study due to unequivocal clinical progression. Thirteen patients (93%) had a HRP tumor. Six of these (46%) patients had PR. Median PFS in patients with HPR tumors was 122 days. The most common gene alterations detected by BROCA-HR assay was TP53 (93%) and RB1 (79%). Other DR gene alterations noted from our study samples were MRE11, CKD12 PALB2, ERCC4, FANCB, and BAP1. Conclusions: HRD was infrequent in our mSCLC samples. C+O resulted in objective responses in 46% of mSCLC patients with HRP tumors. Mutations in TP53 and RB1 were the most common gene alterations. Further investigation in warranted to confirm this observation. Clinical trial information: NCT02498613.

Early results of intratumoral INT230-6 alone or in combination with ipilimumab in subjects with advanced sarcomas

11557

Background: Patients have limited treatment options following initial chemotherapy failure. INT230-6, a novel formulation of cisplatin (CIS) and vinblastine (VIN) with an amphiphilic cell penetration enhancer, is designed for intratumoral (IT) administration. Study IT-01 (BMS # CA184-592, NCT 03058289) evaluates INT230-6 alone or in combination with ipilimumab (IPI), an antibody to CTLA-4. INT230-6 dosing is set by a % of the volume of the tumor to be injected. The product has been shown to disperse throughout an injected tumor and diffuse into cancer cells. Cell death leads to recruitment of dendritic and T cells, the effect of which may be augmented by CTLA-4 inhibition as evidenced by increased efficacy of the combination in preclinical models. Historically, checkpoint inhibitors have limited activity in sarcoma. Considering the large volume of drug injected and retained in the tumor, coupled with immune infiltration on biopsies, RECIST response methodology may not capture the benefits of INT230-6 treatment. Methods: IT-01 is an open-label phase 1/2 study that is enrolling adult subjects with locally advanced, unresectable or metastatic sarcoma. INT230-6 was administered IT Q2W for 5 doses alone or with IPI 3mg/kg IV Q3W for 4 doses. The study objectives are to assess the safety and efficacy of IT INT230-6 alone and in combination with IPI. Results: 16 heterogenous sarcoma subjects (13 monotherapy, 3 IPI combination) having a median of 3 prior therapies (0, 8) were enrolled to date. The INT230-6 dose was up to 145 mL (72.5 mg of CIS, 14.5 mg VIN) in a single session (an amount of each agent in excess of standard IV doses). The most common ( > 20%) related TEAEs in sarcoma subjects (n = 16) were localized pain (63%), fatigue (38%), decreased appetite (31%), nausea (31%), and vomiting (25%) most of which were low grade; with only grade 3 TEAE above 5% being anemia (13%). There were no related grade 4 or 5 TEAEs. In 11 evaluable monotherapy subjects, the disease control rate (DCR = CR+PD+SD) was 82%. Basket studies of sarcomas, including chordoma, with Royal Marsden Hospital index (RMHI) scores of 2 or higher report median overall survival (mOS) of 4 months. In this study 75% of monotherapy subjects had a RMHI score of 2 and preliminary estimates of mOS was 21.3 (4.67, NA) months. Pilot immunohistochemistry analysis of 5 paired (pre- and 28 days post-dose) biopsy samples showed substantial tumor necrosis, reduction of viable cancer, a decreased cancer proliferation as measured by Ki67, and increased TILs. Conclusions: Preliminary data shows that INT230-6 administered intratumorally alone or in combination with ipilimumab is well-tolerated in this small, heterogenous sarcoma population. The preclinical cancer cell death and immune infiltration mechanism of action appears to translate to sarcoma subjects. There are early signs of efficacy, DCR and potentially OS, that need to be confirmed in randomized studies. Clinical trial information: 03058289.

Preliminary results of BEAVER: An investigator-initiated phase II study of binimetinib and encorafenib for the treatment of advanced solid tumors with non-V600E BRAF mutations (mts)

e15038

Background: Recurring oncogenic non-V600E BRAF mts have been identified in many cancer types. Preclinical data indicate that some BRAF non-V600E mts can be targeted with BRAF + MEK inhibitors. BEAVER is an investigator-initiated study designed to test the safety and efficacy of binimetinib and encorafenib (B+E) in patients (pts) with non-V600E BRAF mts. Methods: Key eligibility criteria are: pts with advanced solid tumors with BRAF non-V600E activating (class 1 and 2) or inhibitory (class 3) mts, and no prior BRAF/MEK inhibitors. Pts receive binimetinib (45mg PO BID) and encorafenib (450mg PO daily) on a 28-day cycle until intolerable toxicity or progression. The primary objective is OR rate (ORR) as per RECIST 1.1. In this Simon 2-stage trial, ≥1 of 7 pts need to have an objective response (OR) before commencing second stage of study (26 pts total). Secondary objectives include: safety, DCR, PFS, and OS. Exploratory objectives include: genomic profiling of tumors, evaluating circulating tumor DNA dynamics and development of patient derived xenograft (PDX) models. Results: From June 2019 to Feb 2021, 12 pts were screened and 9 pts enrolled; 9 are evaluable for safety and 8 for efficacy. Tumor types were melanoma and colon (n=2 each), as well as gallbladder, lung, breast and uterine cancers (n=1 each). Median age was 62 yrs (range 40-72). Median number of prior treatments was 2 (range 0-6). 1 pt had a class 1, 3 pts had class 2, and 5 pts had class 3, non-V600E BRAF mts. The median number of cycles was 2 (range: 1-7). Common treatment-related adverse events were mostly grade ≤ 2, and included: Blurred vision (78%), fatigue (67%), nausea (44%), vomiting (33%), and rash (33%). Dose reductions were required in 4/9 pts (44%) due to: blurred vision (22%), central serous retinopathy (11%), malaise (11%) and increased lipase (11%). Drug-related grade 3 AEs occurred in 2/9 pts and included: malaise (11%), confusion (11%), fatigue (11%) and increased lipase (11%). All eye toxicities were reversible with dose interruption. ORR was 12.5% (1/8) with one unconfirmed PR in a melanoma pt (BRAF G469S), treated for 6.5 months. One gallbladder cancer pt (BRAF D594N) had SD, and 6 pts had PD as best response. Genomic profiling was performed on archival tumors for 8 pts. Two PDX models were established. Responses to B+E in PDX models mirrored responses in 2 corresponding pts who had PD. Genomic and molecular profiling of pt tumors and corresponding PDXs identified multiple potential mechanisms of B+E resistance including: activation of EGFR and Akt pathways and inactivation of NF1 and Rb1. Conclusions: Preliminary data confirmed the safety of B+E and showed preliminary evidence of anti-tumor activity in advanced cancer pts with non-V600E BRAF mts. This study met the criterion for advancing to stage 2. Enrolment in the BEAVER trial and correlative biomarker analyses are ongoing. Clinical trial information: NCT03839342.

A phase II, open-label, randomized trial of durvalumab (D) with olaparib (O) or cediranib (C) in patients (pts) with leiomyosarcoma (LMS)

11522

Background: The use of immune checkpoint blockade (ICB) in non-inflamed (cold) tumors is associated with limited clinical efficacy. Combination of ICB with certain molecularly targeted agents (MTA) is hypothesized to increase tumor immunogenicity by recruiting tumor infiltrating lymphocytes in cold tumors, such as LMS. Here, we present the results of LMS cohort treated on the DAPPER study (NCT03851614). Methods: LMS pts with ECOG 0-1 were randomized to either D+O (arm A), or D+C (arm B). In a 28-day cycle, D 1500mg i.v. q4w with either O 300mg bid po qd or C 20mg po qd 5d/week were administered. Overall response rates (ORR) were determined using RECISTv1.1. Evaluation of tumor kinetics (TK) was performed by calculating tumor growth rate (TGR) of target lesions on CT images at baseline and on-treatment, adjusted to account for the time difference between scans. TGR is expressed as % tumor growth/week (Ferte C et al. CCR, 2014). Additionally, paired FFPE samples (from baseline and on-treatment biopsies) were assessed using multispectral fluorescent immunohistochemistry (IHC) panel: CD3, CD8, CD20, CD68, FOXP3 and cytokeratin. Tumor areas were identified by a pathologist and immune cells were quantified using InForm image analysis software. Results: 25 metastatic LMS pts were randomized to arm A (n = 11) or B (n = 14) over 21 months. Median age was 53 years, 96% were females and 60% of pts had ≥3 lines of therapy. In 23 evaluable pts, no responses were seen, 7 pts had stable disease (SD) while 16 has progressive disease (PD). TK analysis was evaluable for 18 pts (arm A = 8, B = 10). 5/8 pts (62.5%) in arm A and 6/10 pts (60%) in arm B showed decreased TK (defined as TGRbaseline > TGRon-treatment). In 4/5 (80%) pts who had deceleration of TK in arm A, SD was maintained for ≥6 months. The reduction in TGR on treatment, compared to baseline was significant in arm A but not in arm B (measured as median % tumor growth/week of 0.5 vs 5.1, 95% CI 0.2-4.3, p = 0.035 in arm A; and 1.3 vs 2.9, 95% CI 0.2-2.7, p = 0.088 in arm B). The median PFS of arm A and B were 9 (95% CI 3-12.8) and 4 (95% CI 2.2-4.6) months respectively. There were no statistically significant differences in tumor-infiltrating immune cells when comparing baseline and on-treatment biopsies from arm A or B. In arm A, one pt with SD > 6 months had a 2.5-fold increase in CD8 (CD3+CD8+) T cells and a 7.6-fold increase in macrophages (CD68+). Conclusions: D+O or D+C resulted in stable disease in 30% of pts, mostly on arm A (D+O). TK analysis may identify pts with prolonged SD on treatment. Although a cold-to-hot immunophenotype change was not generally seen, changes in tumor infiltrating immune cell subsets were observed in one patient with prolonged stable disease. These findings support further molecular and immunophenotype characterization in LMS patients treated with D+O or D+C. Clinical trial information: NCT03851614.

SPEARHEAD-1: A phase 2 trial of afamitresgene autoleucel (Formerly ADP-A2M4) in patients with advanced synovial sarcoma or myxoid/round cell liposarcoma

11504

Background: This phase 2, open-label trial (SPEARHEAD-1; NCT04044768) is designed to evaluate the efficacy, safety, and tolerability of afamitresgene autoleucel in 45 patients (pts) with advanced/metastatic synovial sarcoma or Myxoid/Round Cell Liposarcoma (MRCLS). Methods: Eligible pts are HLA-A*02 positive with MAGE-A4-expressing tumors. Pts undergo leukapheresis for collection of autologous T-cells for processing and manufacture into afamitresgene autoleucel cells. Pts were treated with afamitresgene autoleucel doses between 1–10 × 109 transduced T-cells after receiving lymphodepleting chemotherapy. The primary endpoint is overall response rate per RECIST v1.1 by independent review. An independent Data Safety Monitoring Board reviews ongoing safety and benefit: risk during the interventional phase. Results: As of Feb 4, 2021, 32 pts received afamitresgene autoleucel. Of these pts, 59% were male, 87.5% had synovial sarcoma, the median age was 43 yrs (range: 24–73), and they had a median of 3 prior systemic lines of therapy. The MAGE-A4 antigen expression level (histoscore) ranged from 112–300, and the transduced cell dose ranged from 2.7–9.9 x 109. At the data cutoff, 25 pts were evaluable for preliminary efficacy (23 with synovial sarcoma and 2 with MRCLS) and 7 pts (5 with synovial sarcoma and 2 with MRCLS) had insufficient follow-up (<8 weeks follow-up and/or awaiting first scan). Of the 25 evaluable pts, the investigator-assessed responses were: complete response (2 pts), partial response (8 pts), stable disease (11 pts), and progressive disease (4 pts). All responses were confirmed. Nine of the 10 responders had ongoing response at the data cutoff and 3 responders had MAGE-A4 antigen histoscores <200. The most common AEs of any grade (>30% pts) were neutropenia, lymphopenia, nausea, cytokine release syndrome, leukopenia, fatigue, pyrexia, and anemia. Cytokine release syndrome of any grade occurred in 19/32 pts; 95% of those events were ≤Grade 2. No immune effector cell-associated neurotoxicity syndrome (ICANS) has been reported to date. Cytopenia (≥G3) at 4 wks post-infusion was observed in 6 pts (anemia 3 pts, neutropenia 2 pts, and thrombocytopenia 1 pt). Conclusion: These preliminary data demonstrate afamitresgene autoleucel is efficacious and well tolerated in heavily pre-treated pts. Objective responses are reported across a wide range of MAGE-A4 antigen levels and deep responses have been observed. Initial durability data is encouraging. Preliminary response data in SPEARHEAD-1 is comparable to the findings of the prior Phase 1 trial [1]. To date, the safety profile of afamitresgene autoleucel has been favorable, with mainly low-grade cytokine release syndrome and tolerable/reversible hematologic toxicities. [1]. Van Tine BA, et al. CTOS; November 18-21, 2020; Virtual. Clinical trial information: NCT04044768.

Patient experience of early high grade symptomatic adverse events on early phase clinical trials using the PRO-CTCAE

12051

Background: There are limited data describing the patients’ experience of symptomatic adverse events (syAEs) on early phase clinical trials. This information is critical to understand the tolerability of experimental agents. The patient reported outcome version of the CTCAE (PRO-CTCAE) evaluates syAE components such as severity and interference in daily life. The aim of this study was to correlate clinician reported early, high grade (grade 3-4) AEs with patients’ reported experience of these toxicities. Methods: Advanced solid tumor patients (pts) enrolled on early phase clinical trials at Princess Margaret Cancer Centre were surveyed electronically using the full library of 78 items for PRO-CTCAE v1.0, which was administered at baseline (prior to therapy), mid-cycle 1, and mid-cycle 2. AEs on study were recorded by physicians using the CTCAE v4.0. Worst responses for severity items are ‘severe’ and ‘very severe’ and for interference items are ‘quite a bit’ and ‘very much’. A logistic regression model was used to assess the association between CTCAE grade and PRO-CTCAE severity and interference. Results: A total of 292 pts were approached in phase 1 clinics from May 2017 to January 2019, and 219 pts were included in the analysis: median age 60 years (range 18-82), 111 (51%) were male; all were ECOG ≤1. A total of 140 pts (64%) received combination therapy (immunotherapy and targeted therapy), and 73 pts (33%) had received ≥3 previous lines of treatment. In terms of patient reported syAEs, a total of 114 pts (52%) reported a symptomatic AE as either severe or very severe at any timepoint and 79 pts (36%) reported a syAE with an interference that was either ‘quite a bit’ or ‘very much’. With regards to clinician reported AEs, a total of 82 pts (37%) had a clinician reported grade 3 or 4 syAE, and of these 34 pts (41%) reported these as either severe or very severe; and 26 pts (32%) found these AEs interfered with daily life either ‘quite a bit’ or ‘very much’. Additionally 137 pts (66%) had a clinician reported grade 1 or 2 syAE, and of these 39 pts (28%) reported these as either severe or very severe; and 19 (14%) found these AEs interfered with daily life either ‘quite a bit’ or ‘very much’. Higher grade clinician reported syAEs (CTCAE grade 3-4 vs 1-2) was associated with higher patient reported severity levels (odds ratio, OR = 1.78, 95% CI 1-3.16, p = 0.049), and was associated with higher patient reported interference levels (OR = 2.88, 95% CI 1.47-5.64, p = 0.002). Conclusions: A majority of patients had a very negative experience of syAEs on a phase I trial. Higher grades of clinician reported AEs correlated with greater severity and interference with daily living. Future phase I studies could incorporate the PRO-CTCAE and other PRO tools which could inform the tolerability of experimental regimens and enhance the description of symptomatic AEs.

An evaluation of administrative data linkage for measurement of real-world outcomes of large clinical panel sequencing for advanced solid tumors

283

Background: There is limited real-world evidence of impact of large clinical panel sequencing on treatment-matching for patients with advanced solid tumors. The province of Ontario has a single payer, publicly funded health care system. We linked genomic testing results from a prospective province-wide trial, OCTANE (Ontario-Wide Cancer TArgeted Nucleic Acid Evaluation), to administrative data to determine the feasibility of this approach for evaluating survival and the impact of sequencing on treatment matching. Methods: We linked all Ontario patients from Princess Margaret (PM) with panel testing results (tumor-only 555-gene panel) to province-wide administrative data on treatments and outcomes. Patients were recruited from August 2016 to August 2018. Only clinically actionable variants based upon OncoKB annotation (Level 1 and 2) were assessed for genotype-informed treatment matching. Results: All 888 eligible patients were successfully linked to administrative data. Mean age was 58 (±13) years, 635 (71.5%) were female. Most common disease sites were ovary (26.4%), uterus (14.0%), colorectal (11.8%) and breast (9.5%). Administrative data vital status was more complete than trial collected data with 262 of 476 deaths only recorded in administrative data. Median survival was 1.70 years (95% confidence interval 1.50-1.91). 247 (27.8%) had actionable mutations, most commonly PIK3CA (54.7%), BRCA1 (15.8%), BRCA2 (15.0%) and BRAF (8.9%). 37 (15.0%) and 42 (17.0%) patients with actionable mutations received targeted therapy within 6 and 12 months of test report date, respectively. Conclusions: This is the first known feasibility study of linked administrative data to measure outcomes of large clinical panel sequencing for patients with advanced solid tumors. Vital status was more complete with administrative data compared to trial-collected data, and treatment data was successfully linked. About one in twenty-one enrolled patients received genome-informed treatments within 12 months, or about one in six of all patients with actionable mutations. This may be due to short interval follow up, trial and drug access, successful standard of care treatments, early patient deterioration or limited alterations covered by the panel, among other causes.

An increase in serum choline levels to predict progression-free survival (PFS) in patients (pts) with advanced cancers receiving pembrolizumab

3102

Background: Recent work from our laboratory demonstrated that T cell-derived acetylcholine induces vasodilation and increases T cell migration to infected tissues in response to viral infection (Cox et al. Science 2019). Choline acetyltransferase catalyzes the production of acetylcholine from choline and acetyl-CoA, however acetylcholine is challenging to quantify due to its extremely short half-life while choline is stable. This study is the first reported attempt to correlate serum choline levels in patients (pts) with advanced solid tumors receiving pembrolizumab with treatment outcomes. Methods: Blood samples were collected pre-treatment in 106 pts treated with pembrolizumab 200 mg IV Q3W in the investigator-initiated INSPIRE study (NCT02644369). Of these, 81 pts had on-treatment blood samples collected at week 7 (pre-cycle 3). Serum choline was analyzed with an HPLC-tandem mass spectrometry assay. PD-L1 staining was performed in baseline tumor tissues using 22C3 antibody and scored using modified proportion score. Tumor mutational burden (TMB) was calculated based on number of nonsynonymous mutations detected using whole exome sequencing. Multivariable Cox models were used to assess the impact of choline on PFS and OS, while adjusting for cohort, PD-L1 expression and TMB. Results: This pan-cancer group of 106 pts (median age 55, 62% females) comprised of 5 cohorts: squamous cell carcinoma of the head and neck = 19 pts, triple negative breast cancer = 22, high grade serous ovarian cancer = 21, melanoma = 19, mixed solid tumors = 32. With a median follow-up of 11 months, the median PFS = 1.9 months and median OS = 13.9 months for the entire cohort. In univariable analysis adjusted by cohort, baseline serum choline levels in 106 pts did not correlate with PFS or OS. However, an increase in serum choline level at week 7 compared to pre-treatment (D choline) in 81 pts was significantly associated with a better PFS (aHR 0.49, 95% CI 0.28-0.85, p = 0.01), and a trend towards a better OS (aHR 0.57, 95% CI 0.32-1.03, p = 0.064). In multivariable analysis, D choline remains significantly associated with an improved PFS (p = 0.0087) after adjustment for cohort, PD-L1 and TMB. Conclusions: This is the first exploratory report of serum choline levels in pan-cancer pts receiving pembrolizumab. The association between improved PFS and D choline suggests a possible role for the cholingeric system in the regulation of antitumor immunity. Further nonclinical and clinical studies are required to validate this finding.

An evaluation of administrative data linkage for measurement of real-world outcomes of large clinical panel sequencing for advanced solid tumors

e19303

Background: There is limited real-world evidence of impact of large clinical panel sequencing on treatment-matching for patients with advanced solid tumors. The province of Ontario has a single payer, publicly funded health care system. We linked genomic testing results from a prospective province-wide trial, OCTANE (Ontario-Wide Cancer TArgeted Nucleic Acid Evaluation), to administrative data to determine the feasibility of this approach for evaluating survival and the impact of sequencing on treatment matching. Methods: We linked all Ontario patients from Princess Margaret (PM) with panel testing results (tumor-only 555-gene panel) to province-wide administrative data on treatments and outcomes. Patients were recruited from August 2016 to August 2018. Only clinically actionable variants based upon OncoKB annotation (Level 1 and 2) were assessed for genotype-informed treatment matching. Results: All 888 eligible patients were successfully linked to administrative data. Mean age was 58 (±13) years, 635 (71.5%) were female. Most common disease sites were ovary (26.4%), uterus (14.0%), colorectal (11.8%) and breast (9.5%). Administrative data vital status was more complete than trial collected data with 262 of 476 deaths only recorded in administrative data. Median survival was 1.70 years (95% confidence interval 1.50-1.91). 247 (27.8%) had actionable mutations, most commonly PIK3CA (54.7%), BRCA1 (15.8%), BRCA2 (15.0%) and BRAF (8.9%). 37 (15.0%) and 42 (17.0%) patients with actionable mutations received targeted therapy within 6 and 12 months of test report date, respectively. Conclusions: This is the first known feasibility study of linked administrative data to measure outcomes of large clinical panel sequencing for patients with advanced solid tumors. Vital status was more complete with administrative data compared to trial-collected data, and treatment data was successfully linked. About one in twenty-one enrolled patients received genome-informed treatments within 12 months, or about one in six of all patients with actionable mutations. This may be due to short interval follow up, trial and drug access, successful standard of care treatments, early patient deterioration or limited alterations covered by the panel, among other causes.

Mapping PRO-CTCAE responses to clinician-graded adverse events, dose reductions, interruptions, and discontinuations in phase I cancer trials

2014

Background: Typically symptomatic adverse events (sy-AEs) on clinical trials are reported by clinicians using the CTCAE. To complement clinician collected sy-AEs and understand tolerability better, the patient report outcome version of the CTCAE (PRO-CTCAE) has been developed to provide the patient (pt) perspective on severity of AEs (graded scale 0-4) and their interference in daily life (scale 0-4). The aim of this study was to correlate PRO responses with the grade (G) of AEs, dose interruptions/reductions and dose limiting toxicities (DLTs). Methods: Pts enrolled on phase 1 clinical trials at Princess Margaret were surveyed electronically on tablet using the full library of items for PRO-CTCAE. The PRO-CTCAE was administered at baseline (prior to therapy), mid-cycle 1, and mid-cycle 2. AEs on study were recorded by physicians using the CTCAE. The electronic medical records were analyzed for an association between reported sy-AEs and PRO score. Summary statistics were used to describe patient and disease characteristics, as well as the outcomes. Spearman’s method was used to correlate PRO severity and interference responses. Logistic regression was used to assess which factors were associated with CTCAE G 3-4 vs G 2 AEs. Results: We analyzed 158 pts: median age 60yrs, 77 (49%) were male; all were ECOG ≤1 and 22, 55 and 81 pts completed 1, 2 and 3 surveys, respectively. Clinician reported G2, 3 and 4 sy-AEs occurred in 81, 47 and 3 pts, respectively and all of these were related to a PRO item except 5% (4/81), 9% (4/47) and 33% (1/3), respectively because either the AE occurred after 3rd time point or patient not able to complete the PRO (encephalitis). Sy-AEs causing dose interruptions, reductions, DLTs and discontinuations occurred in 45 (28%), 12 (7.5%), 5 (3%) and 12 (7.5%) pts, respectively; with a corresponding PRO item in 40 (89%), 12 (100%), 4 (80%) and 11(92%) pts, respectively. For patients who had CTCAE G2, G3/4 AEs, interruptions and discontinuations, their severity and inference levels were positively correlated (coefficient 0.49, p < 0.001; 0.45, p < 0.001 0.59, p < 0.001, 0.86, p < 0.001). Dose interruptions (p = 0.0027) and reductions (p = 0.0061) were significantly associated with G3-4 compared to G2 AEs. Conclusions: This is the first time an association between PRO-CTCAE severity and interference; and CTCAE G2, 3, 4 AEs, dose interruptions and discontinuations has been demonstrated. Additional modelling and more patient data are being analyzed to explore the relationship.

Preliminary efficacy data of triple-negative breast cancer cohort of NCI 9881 study: A phase II study of cediranib in combination with olaparib in advanced solid tumors

1077

Background: Cediranib, a pan-vascular endothelial growth factor receptor tyrosine kinase inhibitor, suppresses expression of BRCA1, BRCA2, and RAD51 and increases sensitivity of tumors to poly-(ADP-ribose) polymerase (PARP) inhibitors in vitro. Olaparib, a PARP inhibitor, demonstrates clinical efficacy in patients with germline BRCA1/2 mutations and HER2-negative metastatic breast cancer. We therefore tested the anti-tumor activity of the combination of cediranib and olaparib in patients (pts) with metastatic triple-negative breast cancer (TNBC). Methods: This multi-institutional, two-stage, phase II study enrolled patients with metastatic TNBC previously treated with a minimum of one prior line of systemic therapy in the advanced setting. Patients were treated with cediranib 30mg po daily plus olaparib 200mg po BID until disease progression or unacceptable toxicity. The primary endpoint was objective response rate by RECIST v1.1. Baseline tumor biopsies were obtained for biomarker analyses. Results: Baseline characteristics of the 37pts enrolled are summarized below. The overall objective response rate was 14% (95% CI: 0.025, 0.2453). Median duration of response was 2.0 months (mos) with a range of 1.8 to 6.3 mos. Disease control rate ((# of pts with CR, PR or SD)/(# of evaluable pts)) was 81% (95% CI: 0.6846, 0.937). Median PFS was 3.7 mos (95% CI: 2.1, 4.3). Grade 3/4 adverse events (G3/4 AEs), irrespective of attribution, occurred in 25 of 38 (66%).G3/4 AEs occurring in > 5% of pts were hypertension (24%) and dyspnea (11%), diarrhea (8%) vomiting (8%). Conclusions: The cediranib/olaparib combination resulted in promising objective responses in 14% of biomarker-unselected patients with heavily pre-treated, metastatic TNBC. The regimen required prompt initiation of antihypertensives, but AEs were overall manageable. Analyses of mutation status in homologous recombination DNA repair genes are ongoing and will be correlated with clinical outcome. Clinical trial information: NCT02498613 . [Table: see text]

Circulating tumor DNA dynamics as prognostic and predictive biomarkers of response to pembrolizumab in patients with virally-related tumors (VRT) treated within the INSPIRE study

3068

Background: We previously showed a correlation between circulating tumor DNA (ctDNA) dynamics and response to pembrolizumab in a cohort of mixed tumors treated in the INSPIRE study (Yang et al, ESMO 2019). We investigated the prognostic and predictive value of ctDNA dynamics in patients (pts) with VRT. Methods: Pts with VRT (HPV+ squamous cell carcinoma (SCC), EBER+ nasopharyngeal carcinoma (NPC) and MCPyV+ Merkel carcinoma (MC)) and a control cohort of non-VRT (HPV- head and neck SCC) treated with single-agent pembrolizumab were selected for the analysis. ctDNA was assayed at baseline and start of cycle 3 using a pt-specific amplicon-based NGS assay (Signatera). Samples were considered ctDNA positive if ≥2 of 16 pt-specific targets met the qualifying confidence score threshold. Whole exome sequencing (WES) performed in baseline tumor tissue; presence of HPV, EBV and MCPyV in tumor determined through bioinformatic analysis of WES data (VirusFinder, PMID23717618). Changes in tumor size (mm) and response data using RECIST 1.1 were collected. Progression-free survival (PFS) and overall survival (OS) were estimated by Kaplan-Meier method. Results: Twenty pts with VRT (HPV+ head and neck = 8, cervical = 2 and anal = 2 SCC; EBER+NPC = 2; MC = 6) and 11 pts with non-VRT were included. Median follow-up: 11 months (0,5-11). Treatment response: VRT 6 responders (CR + PR + SD > 18weeks) and 14 non-responders (SD < 18 weeks + PD); non-VRT 3 responders and 8 non-responders. Median OS and PFS for all pts were 10.61 and 3.2 months, respectively. No differences in PFS (p = 0.60) nor OS (p = 0.66) were observed among responders between VRT and non-VRT. Among non-responders, VRT had significantly higher OS but not PFS when compared to non-VRT (HR 0.30, p = 0.01 and HR 0.82 p = 0.62, respectively). VRT had quantitatively higher ctDNA at baseline vs non-VRT (Mean 7.9 vs 0.4 ng, p < 0.001). ΔctDNA (Change in ctDNA between baseline and cycle 3) strongly correlated with changes in tumor measurements and response by RECIST 1.1 (Spearman Rho = 0.75) and was associated with survival regardless of viral status (Table). Conclusions: ΔctDNA strongly correlated with changes in tumor response and survival in both VRT and non-VRT. Higher baseline ctDNA was found in VRT. Correlation with circulating viral DNA and radiomics analyses is on-going. [Table: see text]

Safety and activity of autologous T cells with enhanced NY-ESO-1–specific T-cell receptor (GSK3377794) in HLA-a*02+ previously-treated and -untreated patients with advanced metastatic/unresectable synovial sarcoma: A master protocol study design (IGNYTE-ESO)

TPS11571

Background: T cells modified to target NY-ESO-1 have shown encouraging activity in HLA-A*02+ patients with NY-ESO-1–positive synovial sarcoma. NY-ESO-1 is a cancer/testis antigen that is expressed across multiple tumor types and highly expressed in synovial sarcoma. NY-ESO-1 TCR T (GSK3377794) are autologous polyclonal T cells transduced by a self-inactivating lentiviral vector to express an affinity-enhanced TCR able to recognize NY-ESO-1 epitope in complex with HLA-A*02. Ongoing trials are evaluating GSK3377794 in multiple solid tumors and multiple myeloma. Methods: This study (NCT03967223) uses a Master Protocol design that allows investigation of GSK3377794 in multiple tumor types under the same protocol in separate substudies. The first two are single-arm substudies in patients with advanced metastatic or unresectable synovial sarcoma: treatment-naïve (1st line [1L], substudy 1; n = 10 planned) and progressing after anthracycline-based chemotherapy (2L+, substudy 2; n = 55 planned). Patients must be aged ≥10 years, have adequate organ function, ECOG performance status 0–1, measurable disease, and no central nervous system metastases. Excluded prior treatments include gene therapy with an integrating vector or NY-ESO-1–specific T cells, vaccine or targeting antibody, or allogeneic stem cell transplant. Patients will undergo leukapheresis and manufacture of GSK3377794; lymphodepletion then GSK3377794 infusion, followed by safety and disease assessments; and long-term follow-up for 15 years (under a separate protocol). The primary objective of substudy 2 is overall response rate per RECIST v1.1 by central independent review. Secondary objectives include time to response, duration of response, disease control rate, progression-free survival, overall survival, plus safety and tolerability. Exploratory objectives include assessment of the correlation of T-cell persistence with safety, clinical responses, and infused T-cell phenotype. Evaluation of quality of life and daily functioning of patients will also be assessed. Enrollment began in December 2019. These data are presented on behalf of the original authors with their permission. A similar presentation (P453) was presented at the SITC Annual Meeting, National Harbor, MD, USA, Nov 6–10, 2019. Funding: GlaxoSmithKline (208467) Clinical trial information: NCT03967223 .

Phase II basket trial of olaparib and durvalumab in patients (pts) with isocitrate dehydrogenase (IDH) mutated solid tumors

TPS3167

Background: Somatic IDH mutations are common in low grade gliomas, and rare in other solid tumors with the exception of intrahepatic cholangiocarcinoma (ICA) and certain subtypes of chondrosarcoma. IDH mutations confer a gain-of-function neomorphic activity, such that mutant IDH enzymes preferentially convert αKG to 2-hydroxyglutarate (2HG), resulting in abnormal accumulation of 2HG. 2HG competitively inhibits αKG-dependent dioxygenases, many of which are involved in DNA repair. Preclinical studies show that IDH mutated cancer cells have defective homologous recombination repair and are exquisitely sensitive to poly (adenosine 5’-diphophate-ribose) polymerase (PARP) inhibition. Methods: This is a single arm phase II basket study (NCT03991832). Pts with IDH mutated solid tumors are divided into three cohorts; A: low-grade glioma; B: cholangiocarinoma; C: all other solid tumors. Pts are treated with olaparib 300 mg twice daily continuously and durvalumab 1500 mg every 4 weeks until progression, intolerable toxicity or consent withdrawal. Radiological assessment is performed after every 2 cycles of study treatments. Major eligibility criteria include IDH mutation by immunohistochemistry or sequencing, up to 2 lines of systemic therapy for advanced disease, performance status 0 – 2 and adequate organ function. Pts are excluded if they received prior PARP inhibitors and anti-PD-1/PD-L1 antibody. The Simon’s optimal 2-stage design is applied for Cohorts A and B. 10 pts will be enrolled in each of Cohort A and B initially. If 2 or more partial responses (PR) are seen in these 10 pts, additional 19 pts will be enrolled for a total of 29 pts in that cohort. The combination is considered to be of clinical interest for further development if ≥ 6 PRs are seen in each cohort. Cohort C will enroll 20 pts. Archival tumor tissues and serial blood samples will be collected on study. 2HG levels will be measured and correlated with responses. The study was activated in December 2019. 3 pts have been enrolled into Cohort B. Clinical trial information: NCT03991832 .

SPEARHEAD-1: A phase II trial of ADP-A2M4 SPEAR T cells in patients with advanced synovial sarcoma or myxoid/round cell liposarcoma

TPS11569

Background: ADP-A2M4 specific peptide enhanced affinity receptor (SPEAR) T-cells are genetically engineered to target MAGE-A4+ tumors in the context of HLA-A*02. MAGE-A4 has been described as having high expression in synovial sarcoma (SS) and myxoid/round cell liposarcoma (MRCLS) [1, 2]. This Phase 2 trial was initiated based on the favorable benefit:risk profile of ADP-A2M4 observed in a Phase 1 trial (NCT03132922) of ADP-A2M4 which demonstrated compelling clinical responses in patients with SS. Methods: This Phase 2, open-label trial (SPEARHEAD-1; NCT04044768) is designed to evaluate the efficacy, safety and tolerability of ADP-A2M4 in patients with advanced/metastatic SS or MRCLS who are HLA-A*02 positive and whose tumors express the MAGE-A4 protein. Enrolled patients are to undergo apheresis, and their isolated T-cells are then transduced with the MAGE-A4c1032 TCR, and expanded. Prior to ADP-A2M4 infusion, patients are to receive lymphodepleting chemotherapy consisting of fludarabine (30 mg/m2/day x 4 days) and cyclophosphamide (600 mg/m2/day x 3 days). Patients are to receive 1 – 10 × 109 transduced T-cells. An independent Data Safety Monitoring Board will review ongoing safety and benefit:risk during the interventional phase of the study. Disease will be assessed by independent review per RECIST v1.1 by CT/MRI at weeks 4, 8, 12, 16, 24, and every 2 months thereafter until confirmed disease progression. As of 24 Jan 2020, there were 17 clinical sites open in the US, one in Canada, and two in Spain. References: 1. Iura K, et al. Cancer-testis antigen expression in synovial sarcoma: NY-ESO-1, PRAME, MAGEA4, and MAGEA1. Human Pathology 2017; 61:130-139. 2. Iura K, et al. MAGEA4 expression in bone and soft tissue tumors: its utility as a target for immunotherapy and diagnostic marker combined with NY-ESO-1. Virchows Archiv 2017;471:383–392. Clinical trial information: NCT04044768 .

Preliminary efficacy data of platinum-pretreated small cell lung cancer (SCLC) cohort of NCI 9881 study: A phase II study of cediranib in combination with olaparib in advanced solid tumors

9065

Background: Cediranib, a pan-vascular endothelial growth factor receptor tyrosine kinase inhibitor, suppresses expression of BRCA1, BRCA2, and RAD51 and increases sensitivity of tumors to poly-(ADP-ribose) polymerase (PARP) inhibitors in vitro. Olaparib, a PARP inhibitor, demonstrated clinical efficacy in patients with advanced solid tumors carrying a germline BRCA mutation. We therefore tested the anti-tumor activity of cediranib and olaparib combination in patients (pts) with advanced solid tumors. Here, we report the data from the SCLC cohort. Methods: This multi-institutional, two-stage, phase 2 study enrolled pts with metastatic SCLC previously treated with a minimum of one prior line of platinum-based chemotherapy in advanced setting. Patients were treated with cediranib 30mg po daily plus olaparib 200mg po BID until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) by RECIST v1.1. Baseline tumor biopsies were obtained for biomarker analyses. Results: Baseline characteristics of the 25 pts enrolled are summarized below. The overall ORR rate was 28% (95% CI: 0.104,0.456). Median duration of response was 3.8 months (mos). Six of 8 pts had an objective response lasting longer than 3 mos up to 10.3 months. Disease control rate (# of pts with CR, PR or SD / # evaluable pts) was 88% (95% CI: 0.75,1.01). Median progression free survival was 4.1 mos (95% CI: 2.3, 6.2). Median OS was 5.5 mos (95% CI: 3.4, NA). Grade 3/4 adverse events (G3/4 AEs), irrespective of attribution, occurred in 14 of 25 (56%). G3/4 AEs occurring in > 10% of pts were hypertension (21%), fatigue (17%) and weight loss (13%). Conclusions: The cediranib/olaparib combination resulted in promising clinical activity with ORR of 28% in biomarker-unselected pts with platinum-pretreated SCLC. The regimen required prompt initiation of antihypertensives, but AEs were overall manageable. Analyses of mutation status in homologous recombination DNA repair genes are going and will be correlated with clinical activity. Clinical trial information: NCT02498613. [Table: see text]

Characterization and outcomes of patients enrolled to multiple phase I cancer trials

PURPOSE

Some patients who participate in early phase cancer trials enroll to more than one trial. Whether these patients have different characteristics or outcomes than patients who enroll to a single phase I trial is unknown.

METHODS

The study included all patients who participated in the solid tumor drug development program of the Princess Margaret Cancer Centre, a specialized academic cancer center, from July 2014 to January 2017. Patients sequentially enrolled to multiple phase I trials were compared to those enrolled in a single trial according to demographics, clinical characteristics, reported toxicities and prognosis.

RESULTS

The study cohort included 328 patients, including 61 (19%) enrolled to multiple phase I trials and 267 (81%) enrolled to a single phase I trial. Demographics, comorbidities, performance status, cancer site and time between initial diagnosis and initial enrollment to the phase I program were comparable between both groups. Patients enrolled to multiple phase I trials received more previous non-trial treatment lines (median 3 versus 2, p < 0.001) and had a higher average response rate on phase I trials (18% versus 10%, p = 0.03). Toxicity data, including number of any adverse events (AEs), grade 3/4 AEs, serious AEs and dose-limiting toxicities were comparable between both groups. Time to disease progression and time to last documented follow-up were also comparable between both groups.

CONCLUSIONS

Patients enrolled to multiple phase I trials and those enrolled to a single trial had similar toxicity and prognostic profiles. These patients do not introduce bias into early-phase cancer trials results.

ANNOUNCE: A randomized, placebo (PBO)-controlled, double-blind, phase (Ph) III trial of doxorubicin (dox) + olaratumab versus dox + PBO in patients (pts) with advanced soft tissue sarcomas (STS)

LBA3

Background: Dox is standard therapy in STS. In a Ph 2 trial, olaratumab (a human IgG1 antibody targeting PDGFRα) + dox improved overall survival (OS) and progression-free survival (PFS) vs dox. ANNOUNCE aimed to confirm the OS benefit in advanced STS. Methods: Adult pts with unresectable locally advanced or metastatic STS, anthracycline-naïve, and ECOG PS 0-1 were eligible. Pts were randomized 1:1 to olaratumab (20mg/kg Cycle 1, 15mg/kg subsequent cycles) or PBO on Days 1 and 8 of each 21-day cycle combined with dox (75mg/m2) on Day 1 for up to 8 cycles. After 8 cycles, pts with disease control continued olaratumab or PBO until progression or toxicity. Randomization was stratified by histology, prior systemic therapy, ECOG PS, and geographic region. Dexrazoxane use was allowed to mitigate dox-related cardiotoxicity. Primary endpoints were OS in the intent-to-treat (ITT) population and/or leiomyosarcoma (LMS) subset of the ITT population; the study was designed to be positive if either primary endpoint was met. Secondary endpoints included PFS, response/disease control rates, safety, and pharmacokinetics. Results: 509 pts were randomized: 258 in the investigational and 251 in the control arm. Baseline pt characteristics were well balanced. Dexrazoxane was received by 63.0% vs 65.1% of pts (investigational vs control arm, respectively, for all data). In the ITT population, median OS was 20.4 vs 19.8 months (m) (HR=1.05, 95% CI: 0.84-1.30; p = 0.69) and was 21.6 vs 21.9 m in LMS pts (HR=0.95, 95% CI: 0.69-1.31; p = 0.76). Median PFS was lower in the investigational arm in the ITT population (5.4 vs 6.8 m; HR=1.23, 95% CI: 1.01-1.50; p = 0.04) and in LMS pts (4.3 vs 6.9 m, HR=1.22, 95% CI: 0.92-1.63; p = 0.17). Median dox exposure was 6 vs 7 cycles. Safety was similar between arms. Olaratumab serum concentrations reached levels expected from prior trials. Additional subgroup/biomarker results will be presented. Conclusions: ANNOUNCE did not confirm that olaratumab + dox, followed by olaratumab monotherapy, improves OS over dox in pts with advanced STS. Further analyses are warranted to explore the inconsistent outcomes between the Ph 3 and Ph 2 studies. Clinical trial information: NCT02451943.

Hyperprogressive disease in advanced triple-negative breast cancer (aTNBC) treated with immunotherapy (IO)

1086

Background: Hyperprogression of disease (HPD), a rapid acceleration of tumor growth rate (TGR) has been reported with IO in other tumor types. Here, we explore HPD in aTNBC. Methods: A retrospective chart review identified aTNBC patients who consented for IO clinical trials at Princess Margaret Cancer Centre between June 2013 and June 2018. Demographic data, medical history, details of trial enrolment and RECIST 1.1 response to study treatment were recorded. Patients with RECIST 1.1 measurable disease on CT scans or physical examination before trial entry, at trial baseline and at protocol-defined interval following IO start were evaluable for TGR as defined by Champiat et al. Clin Cancer Res 2017. HPD defined as a ≥2-fold increase in TGR between baseline and on-trial restaging assessment. Univariable logistic regression used to identify variables [age, co-morbidity index, prognostic index, performance status, distant disease free interval (dDFI), lactate dehydrogenase, no. of metastatic sites, visceral disease and no. of prior treatment lines] associated with HPD. Overall survival (OS) curves were estimated with the Kaplan-Meier method and compared by the log-rank test. Results: 99 patients with aTNBC consented for 15 IO clinical trials, 60% IO monotherapy, 22% chemotherapy+/-IO and 18% IO combinations. Median age 52 (range 25-78), median no. of lines of prior systemic therapy for advanced disease 1 (range 0-8). 15% had de-novo metastatic disease, 58% recurred after a dDFI of < 3 years and 25% after a dDFI of > 3 years. 61% had < 3 metastatic disease sites, and 71% had metastases involving the viscera. 66 received IO treatment, 40 patients (20 monotherapy, 7 IO combination, 13 chemotherapy+/-IO) were evaluable for TGR. Median TGR pre-IO was 74.3 (range -17 – 1680) and post-IO was 2.5 (-71.4 – 223). 4 patients (10%) met criteria for HPD. All 4 treated with monotherapy PD1 inhibitor and received at least 2 further lines of therapy post-trial; 1 patient treated with IO as first-line therapy, 3 in the second or later lines. There was no significant difference in the overall OS of patients with HPD and patients who did not meet definition for HPD HR 0.89, (95% CI: 0.26-3.01; p = 0.41). Univariable analysis did not identify factors associated with HPD. Conclusions: HPD was observed in 10% of aTNBC treated on IO clinical trials. HPD was not associated with worse survival outcomes or known prognostic factors in our analysis.

Is PAX3-FOXO1 associated with worse outcome in adults with rhabdomyosarcoma (RMS)?

e22525

Background: Rhabdomyosarcoma (RMS) is a rare soft tissue sarcoma in adults. The PAX3-FOXO1 fusion gene is associated with alveolar rhabdomyosarcoma. PAX3-FOXO1 results from a stable reciprocal translocation of chromosomes 2 and 13, which fuses in-frame the DNA binding domain of PAX3 with the transactivation domain of FOXO1. Occasionally, PAX7-FOXO1 is expressed. In children, the PAX3-FOXO1 fusion gene is associated with worse outcome. We evaluated the prognostic role of FOXO1 fusion status in adults with RMS treated in a single, large volume sarcoma centre. Methods: A retrospective review of adult RMS patients (pts) diagnosed from 1984 to 2018 was done. Information on demographics, treatment, fusion status and survival was collected. Primary favourable site was defined as tumour arising in orbit, non-bladder/prostate genitourinary system and non-parameningeal head and neck. Factors were compared using Fisher’s Exact test. Event-free survival (EFS) was estimated by the Kaplan-Meier method and compared with log rank test. FOXO1 fusion status was coded as FP (fusion positive) or FN (fusion negative). Results: Of 134 pts identified in our database, fusion testing was performed in 55 (41%). Of these, PAX3 fusion was detected in 22 (40%). PAX7 was not detected. The median age of FP and FN pts was 25 yrs (range 18, 90) and 27 yrs (range 18, 65), respectively. Gender distribution was similar between FP and FN. Favourable site was seen in 13 (60%) FP and 21 (64%) FN. Nodal disease was present in 21 (95%) FP and 21 (64%) FN (p = 0.02). Distant metastases were present in 10 (45%) FP and 9 (27%) FN (n.s.). Treatment received was as follows for FP and FN, respectively: chemotherapy (21(95%), 33(100%)), radiation (14(64%), 22(67%)) and surgery (4(18%), 17(52%)). 5-yr EFS for pts without distant metastases was 27% (CI 22.6-76.6) and 46% (CI 21.5 – 70.5) for FP and FN respectively (n.s.). Conclusions: FP and FN RMS occurs in adults of all ages. Similar to children, adults with FP are more likely to present with nodal disease. Our study did not show that fusion status was associated with poorer EFS in adult RMS, however, larger series are needed to confirm this preliminary data.

Clinical characteristics of nonosteogenic, non-Ewing’s sarcoma of the bone: Experience at the Toronto Sarcoma Program

11029

Background: Non-osteogenic sarcoma of the bone is a rare entity comprising a heterogenous group of malignant tumors. Clinical characteristics and outcome data are sparse in the literature. We evaluated the characteristics and long-term outcomes of patients (pts) with this disease. Methods: Pts with non-osteogenic sarcoma of the bone treated at the Toronto Sarcoma Program from 1987-2017 were identified from our institutional sarcoma database. Patient characteristics (ie: age, gender, tumor size, histology, grade, necrosis, tumor location), treatment modality (ie: surgical management, chemotherapy, radiotherapy), and survival information were collected. Survival was estimated by Kaplan-Meier (log-rank). Multi-variate analysis (MVA) was used to evaluate characteristics for sarcoma specific survival. Results: Of 130 pts identified, 106 had non-metastatic disease with a median age of 46 (range 18-89). Male-to-female predominance was 1.5:1. Common histologies were undifferentiated pleomorphic sarcoma (UPS; 42%), leiomyosarcoma (21%), and fibrosarcoma (11%). Tumors were generally high grade (59%) and > 5 cm in size (73%). The majority of pts received chemotherapy (68%), with Cisplatin/Doxorubicin based regimens (95%). R0 resection was achieved in 85% of cases. Survival for the entire cohort, showed a median (m)DFS of 8.13 years (95%CI:2.52-18.02), and a mOS of 11.72 (95%CI:7.00-not reached [NR]). Median sarcoma specific survival was NR, however 15- and 25-year survivals were 60.4% and 52.6% respectively. MVA demonstrated axial tumor location (HR = 13.03; p = 0.005), no chemotherapy (HR = 4.50; p = 0.017) and tumor grade (G2: HR = 36.21; p = 0.012; G3: HR = 20.30; p = 0.015) as risk factors for sarcoma specific death. Tumor size > 10cm (p = 0.085) and necrosis > 90% (p = 0.082) trended towards significance. Conclusions: Non-osteogenic sarcoma of the bone is a rare tumor entity, with a predominant UPS histology. Patient outcomes are reasonable, with measurable long-term survival. Axial tumor location, absence of chemotherapy, and high-grade disease predict for worse survival outcome. Further evaluation with larger data series is warranted to more fully understand this disease.

Phase 1b study of selinexor, a first-in-class selective inhibitor of nuclear export (SINE) compound, in combination with doxorubicin in patients (pts) with locally advanced or metastatic soft tissue sarcoma (STS)

3123

Background: Selinexor is a first-in-class SINE compound with single-agent activity in STS. We undertook this study to determine the safety, tolerability and efficacy of selinexor in combination with doxorubicin in pts with incurable STS. Methods: This phase 1b study was conducted using a bayesian model (modified toxicity probability index). Patients with locally advanced or metastatic STS received selinexor at either 60 or 80mg weekly PO plus doxorubicin (75mg/m2 IV q21 days, max 6 cycles). Pts with stable disease (SD) or better (per RECIST 1.1 criteria) after 6 cycles of combination treatment received selinexor monotherapy until disease progression or unacceptable toxicity. Disease assessments were made with standard imaging after every 2 cycles. Results: 24 pts (19F/5M, ECOG 0/1: 12/12, median age 58.5 years [range 34-74]) were enrolled. Disease subtypes included leiomyosarcoma (n = 6), malignant peripheral nerve sheath tumor (n = 3) and other sarcomas (n = 15). Three pts at 60mg selinexor and 21 pts at 80mg selinexor were treated. The most common G3 drug related adverse events were hematological, neutropenia n = 13 (54%), anemia n = 6 (25%). There were 4 dose-limiting toxicities (2 febrile neutropenia, 1 vomiting and 1 unresolved fatigue) all at the 80mg dose level, but does not satisfy criteria for maximum tolerated dose. Two patients had clinically significant and relevant drop in ejection fraction, presenting with cardiac symptoms. Of the 24 evaluable pts 4 (17%) had a partial response, 16 (67%) had SD as best response and SD > 16 weeks was seen in 13 pts (54%). PK analysis of selinexor did not demonstrate changes compared to single agent profile. The estimated median PFS and OS are 5.5 (95% CI:4.1-7.0) and 9.4 (6.6-13.8) months. Conclusions: Our initial data demonstrate that the combination of selinexor at 80mg with doxorubicin is tolerable and is associated with clinical benefit. Longer term follow up of available patients will be needed to understand toxicity profile. Clinical trial information: NCT03042819.

Bespoke circulating tumor DNA (ctDNA) analysis as a predictive biomarker in solid tumor patients (pts) treated with single-agent pembrolizumab (P)

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Background: Limited data exist in the clonal dynamics of serial ctDNA as a predictive biomarker in advanced solid tumor pts receiving immune checkpoint blockade. Methods: Pts with mixed solid tumors received single agent P (anti-PD-1) 200 mg IV Q3wks in the investigator-initiated phase II INSPIRE trial (NCT02644369). ctDNA was assayed at baseline (B) and start of cycle 3 (C3) using a pt-specific amplicon-based NGS assay (Signatera™). Samples were considered ctDNA positive if ≥2 of 16 pt-specific targets met the qualifying confidence score threshold. Results: Results of 70 pts are presented. Demographics: male 46%; median age=60 yrs (range 21–82); head and neck (20%), triple negative breast (14%) and ovarian (14%) cancers comprised the major malignancies. Median no. of P cycles=4 (range 2–35); follow up was 14m (range 2–29); RECIST responses: CR 2.9% (n=2), PR 17% (n=12), CBR (CR+PR+SD≥6 cycles) 31% (n=22), RECIST/clinical PD (n=43/10; 65%/15%). Median PFS=3.3m and median OS=17.8m. 68/70 pts had ctDNA detected at baseline (median=16/16 variants) demonstrating 97% sensitivity. Table shows correlation of ΔctDNA (ctDNAB compared to ctDNAC3) with clinical efficacy parameters, whereas ctDNAB values did not reach statistical significance. Conclusions: A strong correlation exists between ΔctDNA with OS, PFS, CBR and ORR with P, suggesting it is a potential predictive biomarker in pts with mixed solid tumors. Clinical trial information: NCT02644369. [Table: see text]

Immune signature and molecular profiling of radiation-induced sarcoma (RIS)

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Background: RIS is a rare subset of soft tissue sarcoma (STS) with poor prognosis and limited treatment options. We hypothesize that subsets of STS that carry genomic complexity, such as RIS, will have a neoepitope and immune signature that predicts response to immunotherapy as these mutations act as strong antigenic targets for eliciting immune response. Methods: Cases of RIS were identified from an institutional database. Formalin fixed paraffin embedded (FFPE) samples were stained for PD-1, PD-L1, CD3, CD4, CD8. Immune scoring was performed. Tumor-infiltrating lymphocytes (TILs) were assessed using a 4-tiered scale: 0 (no lymphocytes); 1 (1-10/HPF); 2 (11-50/HPF), 3 (51-100/HPF); 4 ( > 100/HPF). TIL staining with PD-1 and PD-L1 was also scored whereby the overall percentage of positive cells on the entire slide was quantified. Tumor DNA was extracted from FFPE samples and underwent whole exome sequencing (WES). Results: FFPE samples from 20 cases of RIS were selected for analysis. PD-1 and PD-L1 expression (threshold set at ≥ 1% positive cells) was seen in 35% and 45% of the cases respectively. CD3+, CD4+, CD8+ T cell infiltration (threshold set ≥ 11 cells /HPF) was seen in 45%, 15% and 20% of cases respectively. 12 exomes of unpaired RIS samples were successfully sequenced. The most common histologies were angiosarcoma (n = 3), undifferentiated spindle cell sarcoma (n = 3), de-differentiated liposarcoma (n = 2) and radiation induced spindle cell sarcoma (n = 2). Provisional analysis did not reveal any pattern to the relative mutational burden between the RIS’s. There does however seem to be relatively higher rate of mutation than that seen in other cancer subtypes. Half the samples had at least one pathogenic or likely pathogenic variant. Different HRAS mutations were seen in two samples (sarcoma NOS and angiosarcoma) and FGFR4 mutation was present in two samples, both spindle cell sarcomas. Conclusions: To our knowledge this is the first study to investigate the immune profile in RIS. Up to 45% of these tumors were positive for PD1/PDL1 expression, as well as presence of tumour infiltrating lymphocytes. Results from WES demonstrate that RIS may benefit from immunotherapy due to a relatively higher mutational burden.