Retrospective world-wide registry on the efficacy of immune checkpoint inhibitors in alveolar soft part sarcoma: Updated results from sixty patients

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Background: Alveolar soft-part sarcoma (ASPS) is a highly metastasizing ultra-rare sarcoma subtype, frequently affecting young adults. Conventional cytotoxic drugs are not effective in ASPS, but antiangiogenics demonstrated significant improvement in tumor burden reduction and PFS in the only ever conducted comparative trial. Immune check-point (PD-1/PD-L1) inhibitors (ICI) are emerging promising drugs in the therapy of ASPS, from small reported retrospective and prospective series. A world-wide registry has been set up with the aim of exploring the efficacy of ICI in ASPS. Methods: Data from adult patients (pts) diagnosed with ASPS and treated with PD- 1/PD-L1 inhibitors for advanced disease in expert sarcoma centers from Europe, Australia and US was retrospectively collected. IRB approval was obtained. Demographics, data related to treatments and outcome were considered. Radiologic assessment was based on RECIST 1.1. Progression-free (PFS) and overall survival (OS) were calculated with Kaplan-Meier method. An updated analysis of this series is presented here. Results: Sixty ASPS pts (27 female/33 male) with a median age at diagnosis of 25y (range 3-61) were registered. Primary tumor arose in limbs in 47 pts (78%) and 41 pts (68%) were metastatic at diagnosis. 52/60 pts (87%) had received previous systemic therapy (including chemotherapy in 19 pts and antiangiogenics in 47pts), with a median of one previous line (0-6). All pts received ICI for metastatic disease. Immunotherapy regimens consisted of monotherapy in 31 pts (52%) and combination in 29 pts (48%) (23 with an antiangiogenic agent). 29/60 pts (48%) received ICI within a clinical trial. Among the 52 evaluable pts, there was 1 complete response (CR) and 20 partial responses (PR) (ORR 40.4%). After a median follow-up of 21 months -mos- (range 4-59), 37/60 pts have progressed to ICI, with a median PFS of 13.4 mos (95% CI 10.1-16.7). Eleven pts received a subsequent line of ICI with a median PFS of 26 mos (95%CI 0-57). 16 pts have died, being the median OS from ICI initiation 38 mos (95% CI 33-43). The 12-mos and 24-mos OS rates were 94% and 70% respectively. Conclusions: This registry constitutes the largest available series of ASPS treated with immune check-point inhibitors. Our results suggest that treatment with ICI provide long-lasting disease control and prolonged OS in pts with advanced ASPS, an ultra-rare entity with limited active therapeutic options. The results on subsequent ICI lines suggest a lack of cross-resistance among different ICI therapies.

A phase 1b study of avelumab plus DCC-3014, a potent and selective inhibitor of colony stimulating factor 1 receptor (CSF1R), in patients with advanced high-grade sarcoma

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Background: Select sarcomas are infiltrated with immunosuppressive myeloid cells. DCC-3014 is an inhibitor of the CSF1R kinase that decreases tumor infiltrating myeloid cells in preclinical models. We hypothesized that DCC-3014 combined with the anti-PDL1 inhibitor avelumab would be safe and tolerable, decrease immunosuppressive myeloid cells, and increase cytotoxic T cells. Methods: This investigator initiated, open label, single center, phase I study of DCC-3014 plus avelumab in patients (pts) with unresectable or metastatic sarcoma utilized a standard 3+3 dose escalation design. DCC-3014 was administered on days 1-3 (loading dose of 20, 30, or 50 mg) followed by oral daily maintenance (10, 14, or 20 mg) in 28-day cycles; 800 mg of IV avelumab was administered q2weeks. The primary endpoint was to determine the recommended phase 2 dose (RP2D). Secondary endpoints defined the adverse event (AE) profile and assessed clinical efficacy. Peripheral blood CD14+Lin-HLA-DRlo myeloid-derived suppressor cells (MDSCs) were measured by flow cytometry. Results: 13 pts were treated; median age was 61 (range 32 – 71), 8 were female, and median prior lines of therapy was 5 (range 2 – 10). Histologic subtypes included leiomyosarcoma (LMS, n = 7), undifferentiated pleomorphic sarcoma (2), dedifferentiated liposarcoma (LPS, 2), synovial sarcoma (1), and pleomorphic LPS (1). The Table lists treatment-related AEs (TRAEs) of any grade (G) occurring in ≥ 10% of pts and all G ≥ 3 TRAEs, sorted by frequency. All pts had at least 1 TRAE. Seven pts (54%) had a G ≥ 3 TRAE. Most TRAEs were either G ≤ 2 or expected on-target effects of CSF1R inhibition. 1 of 6 pts on the highest dose level had a dose limiting toxicity (G4 elevated AST with abdominal pain) that resolved with treatment cessation. The highest dose level was declared the RP2D. Best objective response by RECIST 1.1 was stable disease in 3 pts; 2 had LMS and were treated at the highest dose level. At baseline, the mean proportion of monocytes in peripheral blood samples with an MDSC phenotype was 12.2% (range 7.1 – 19.9). 5 of 7 pts with serial blood samples had decreased circulating MDSCs (mean decrease of 26.9% from baseline to last time point). Conclusions: DCC-3014 combined with avelumab was safe and tolerable. Study therapy decreased circulating MDSCs in select patients; T cell analyses will be reported. Study expansion at the RP2D is ongoing. Clinical trial information: NCT04242238. [Table: see text]

Imaging-based patient inclusion model for clinical trial performance optimization

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Background: In the era of precision medicine, development of new cancer therapies relies strongly on effective selection of target patient population. We hypothesize that computational analysis of imaging data can be used for development of a quantitative population enrichment strategy in clinical trials and thus we aim to establish an appropriate framework for this analysis. Methods: This hypothesis was tested among soft-tissue sarcoma (STS) patients accrued into a randomized Phase III clinical trial (SARC021) that evaluated the efficacy of evofosfamide (Evo), a hypoxia activated prodrug, in combination with doxorubicin (Dox). Notably, SARC021 failed to meet its survival objective (PMC7771354). We tested whether an inclusion/exclusion model based on radiomic analysis and relevant clinical covariates could have been employed to result in a significant treatment benefit of the Evo+Dox combination compared to the standard Dox monotherapy. A total of 163 radiomics features were extracted from lung metastases of 303 patients from the SARC021 trial, divided into demographically matched training and test sets. Stability analysis identified the most reproducible features. Univariable and multivariable models were utilized to discriminate OS in the two treatment groups. Results: A bespoke enrichment framework was established for individualized patient selection, based on model-derived risk score threshold. A radiomic feature, Short Run Emphasis, was identified as the most informative. When combined with tumor histology and smoking history information, an enriched subset (42%) of patients had longer OS in Evo+Dox vs. Dox groups [p = 0.01, Hazard Ratio (HR) = 0.57 (0.36-0.90)], overperforming a clinical-only approach. Application of the same model and threshold value in an independent test set confirmed the significant survival difference (p = 0.002, HR = 0.29 (0.13-0.63), 38% patients included). The breakdown of Dox+Evo treatment benefit depending on proportion of patients included based on the model is shown in the Table. Notably, this process also identified patients most likely to benefit from doxorubicin alone. Conclusions: The study presents a first of its kind radiomic approach for patient enrichment in clinical trials based on a quantitative score. In particular, we have shown that had the novel model been used for selective patient inclusion into the SARC021 trial, it would have met its primary survival objective for patients with metastatic STS.[Table: see text]

Ultra-rare sarcomas: A consensus paper from the Connective Tissue Oncology Society community of experts on the incidence threshold and the list of entities

BACKGROUND

Among sarcomas, which are rare cancers, many types are exceedingly rare; however, a definition of ultra-rare cancers has not been established. The problem of ultra-rare sarcomas is particularly relevant because they represent unique diseases, and their rarity poses major challenges for diagnosis, understanding disease biology, generating clinical evidence to support new drug development, and achieving formal authorization for novel therapies.

METHODS

The Connective Tissue Oncology Society promoted a consensus effort in November 2019 to establish how to define ultra-rare sarcomas through expert consensus and epidemiologic data and to work out a comprehensive list of these diseases. The list of ultra-rare sarcomas was based on the 2020 World Health Organization classification, The incidence rates were estimated using the Information Network on Rare Cancers (RARECARENet) database and NETSARC (the French Sarcoma Network's clinical-pathologic registry). Incidence rates were further validated in collaboration with the Asian cancer registries of Japan, Korea, and Taiwan.

RESULTS

It was agreed that the best criterion for a definition of ultra-rare sarcomas would be incidence. Ultra-rare sarcomas were defined as those with an incidence of approximately ≤1 per 1,000,000, to include those entities whose rarity renders them extremely difficult to conduct well powered, prospective clinical studies. On the basis of this threshold, a list of ultra-rare sarcomas was defined, which comprised 56 soft tissue sarcoma types and 21 bone sarcoma types.

CONCLUSIONS

Altogether, the incidence of ultra-rare sarcomas accounts for roughly 20% of all soft tissue and bone sarcomas. This confirms that the challenges inherent in ultra-rare sarcomas affect large numbers of patients.

Imaging features and clinical course of undifferentiated round cell sarcomas with CIC-DUX4 and BCOR-CCNB3 translocations

OBJECTIVE

To describe the pre-treatment imaging features and clinical course of undifferentiated round cell sarcomas with CIC-DUX4 and BCOR-CCNB3 translocations.

MATERIALS AND METHODS

In this retrospective study, several pre-treatment imaging features (tumor location, size, enhancement pattern, necrosis, flow voids, calcification, and FDG avidity) and the clinical course of patients were evaluated.

RESULTS

In 12 patients with CIC-DUX4 sarcomas (median age, 24 years; range, 12-75), sarcomas were located in the soft tissue (n = 10), bone (n = 1), and lungs (n = 1). On MRI, all 10 CIC-DUX4 sarcomas presented as a large necrotic mass (mean size 6.7 cm, range 2.3-11.3) with 100% demonstrating contrast enhancement, 60% showing flow voids, and 20% demonstrating fluid-fluid levels. On PET, the mean SUVmax was 13.2 (range, 8.5-18.1). Among 12 patients with follow-up, 3 died within a year of diagnosis. The most common site of metastases was the lungs (5/12). In 5 patients with BCOR-CCNB3 sarcomas (median age, 14 years; range, 2-17), sarcomas were located in the spine (n = 2), femur (n = 1), tibia (n = 1), and pelvis (n = 1). On radiograph or CT, 2 were lytic, 3 were sclerotic. Soft tissue calcifications occurred in 40% of BCOR-CCNB3 sarcomas. On MRI, all 3 BCOR-CCNB3 tumors enhanced with 33% demonstrating flow voids and 66% exhibiting necrosis. On PET, the mean SUVmax was 6.3 (range 5.7-6.9).

CONCLUSION

CIC-DUX4 sarcomas often present as necrotic and hypermetabolic soft tissue masses while sarcomas with BCOR-CCNB3 translocations are vascular bone lesions with necrosis at imaging. CIC-DUX4 sarcomas are clinically more aggressive than BCOR-CCNB3 sarcomas.

Avapritinib in unresectable or metastatic PDGFRA D842V-mutant gastrointestinal stromal tumours: Long-term efficacy and safety data from the NAVIGATOR phase I trial

BACKGROUND

PDGFRA D842V mutations occur in 5-10% of gastrointestinal stromal tumours (GISTs), and previously approved tyrosine kinase inhibitors (TKIs) are inactive against this mutation. Consequently, patients have a poor prognosis. We present an updated analysis of avapritinib efficacy and long-term safety in this patient population.

METHODS

NAVIGATOR (NCT02508532), a two-part, open-label, dose-escalation/dose-expansion phase I study, enrolled adult patients with unresectable GISTs. Patients with PDGFRA D842V-mutant GIST were a prespecified subgroup within the overall safety population, which included patients who received ≥1 avapritinib dose. Primary end-points were overall response rate (ORR) and avapritinib safety profile. Secondary end-points were clinical benefit rate (CBR), duration of response (DOR) and progression-free survival (PFS). Overall survival (OS) was an exploratory end-point.

RESULTS

Between 7 October 2015 and 9 March 2020, 250 patients enrolled in the safety population; 56 patients were included in the PDGFRA D842V population, 11 were TKI-naïve. At data cut-off, median follow-up was 27.5 months. Safety profile was comparable between the overall safety and PDGFRA D842V populations. In the PDGFRA D842V population, the most frequent adverse events were nausea (38 [68%] patients) and diarrhoea (37 [66%]), and cognitive effects occurred in 32 (57%) patients. The ORR was 91% (51/56 patients). The CBR was 98% (55/56 patients). The median DOR was 27.6 months (95% confidence interval [CI]: 17.6-not reached [NR]); median PFS was 34.0 months (95% CI: 22.9-NR). Median OS was not reached.

CONCLUSION

Targeting PDGFRA D842V-mutant GIST with avapritinib resulted in an unprecedented, durable clinical benefit, with a manageable safety profile. Avapritinib should be considered as first-line therapy for these patients.

Avapritinib in Patients With Advanced Gastrointestinal Stromal Tumors Following at Least Three Prior Lines of Therapy

BACKGROUND

Most gastrointestinal stromal tumors (GIST) driven by KIT or platelet-derived growth factor receptor A (PDGFRA) mutations develop resistance to available tyrosine kinase inhibitor (TKI) treatments. NAVIGATOR is a two-part, single-arm, dose escalation and expansion study designed to evaluate safety and antineoplastic activity of avapritinib, a selective, potent inhibitor of KIT and PDGFRA, in patients with unresectable or metastatic GIST.

MATERIALS AND METHODS

Eligible patients were 18 years or older with histologically or cytologically confirmed unresectable GIST and Eastern Cooperative Oncology Group performance status ≤2 and initiated avapritinib at 300 mg or 400 mg once daily. Primary endpoints were safety in patients who initiated avapritinib at 300 mg or 400 mg once daily and overall response rate (ORR) in patients in the safety population with three or more previous lines of TKI therapy.

RESULTS

As of November 16, 2018, in the safety population (n = 204), the most common adverse events (AEs) were nausea (131 [64%]), fatigue (113 [55%]), anemia (102 [50%]), cognitive effects (84 [41%]), and periorbital edema (83 [41%]); 17 (8%) patients discontinued due to treatment-related AEs, most frequently confusion, encephalopathy, and fatigue. ORR in response-evaluable patients with GIST harboring KIT or non-D842V PDGFRA mutations and with at least three prior therapies (n = 103) was 17% (95% confidence interval [CI], 10-25). Median duration of response was 10.2 months (95% CI, 7.2-10.2), and median progression-free survival was 3.7 months (95% CI, 2.8-4.6).

CONCLUSION

Avapritinib has manageable toxicity with meaningful clinical activity as fourth-line or later treatment in some patients with GIST with KIT or PDGFRA mutations.

IMPLICATIONS FOR PRACTICE

In the NAVIGATOR trial, avapritinib, an inhibitor of KIT and platelet-derived growth factor receptor A tyrosine kinases, provided durable responses in a proportion of patients with advanced gastrointestinal stromal tumors (GIST) who had received three or more prior therapies. Avapritinib had a tolerable safety profile, with cognitive adverse events manageable with dose interruptions and modification in most cases. These findings indicate that avapritinib can elicit durable treatment responses in some patients with heavily pretreated GIST, for whom limited treatment options exist.

Pexidartinib Long-Term Hepatic Safety Profile in Patients with Tenosynovial Giant Cell Tumors

Background

Pexidartinib is approved in the U.S. for tenosynovial giant cell tumors (TGCTs). Herein, we assessed the hepatic safety profile of pexidartinib across patients with TGCTs receiving pexidartinib.

Materials, and Methods

Hepatic adverse reactions (ARs) were assessed by type and magnitude of liver test abnormalities, classified as (a) isolated aminotransferase elevations (alanine [ALT] or aspartate [AST], without significant alkaline phosphatase [ALP] or bilirubin elevations), or (b) mixed or cholestatic hepatotoxicity (increase in ALP with or without ALT/AST and bilirubin elevations, based on adjudication). Median follow‐up from initial pexidartinib treatment was 39 months (range, 32–82) in 140 patients with TGCTs across clinical studies NCT01004861, NCT02371369, NCT02734433, and NCT03291288.

Results

In total, 95% of patients with TGCTs (133/140) treated with pexidartinib (median duration of exposure, 19 months [range, 1–76]), experienced a hepatic AR. A total of 128 patients (91%) had reversible, low‐grade dose‐dependent isolated AST/ALT elevations without significant ALP elevations. Five patients (4%) experienced serious mixed or cholestatic injury. No case met Hy's law criteria. Onset of hepatic ARs was predominantly in the first 2 months. All five serious hepatic AR cases recovered 1–7 months following pexidartinib discontinuation. Five patients from the non‐TGCT population (N = 658) experienced serious hepatic ARs, two irreversible cases.

Conclusion

This pooled analysis provides information to help form the basis for the treating physician's risk assessment for patients with TCGTs, a locally aggressive but typically nonmetastatic tumor. In particular, long‐term treatment with pexidartinib has a predictable effect on hepatic aminotransferases and unpredictable risk of serious cholestatic or mixed liver injury.

Implications for Practice

This is the first long‐term pooled analysis to report on the long‐term hepatic safety of pexidartinib in patients with tenosynovial giant cell tumors associated with severe morbidity or functional limitations and not amenable to improvement with surgery. These findings extend beyond what has been previously published, describing the observed instances of hepatic toxicity following pexidartinib treatment across the clinical development program. This information is highly relevant for medical oncologists and orthopedic oncologists and provides guidance for its proper use for appropriate patients within the Pexidartinib Risk Evaluation and Mitigation Safety program.

Pexidartinib is approved in the U.S. for treatment of tenosynovial giant cell tumors (TGCT). This article assesses the hepatic safety profile of pexidartinib in TGCT cases and describes risk mitigation procedures designed to identify any instances of serious liver injury as early as possible to better inform prescribers and patients about this drug.

Objective Response Rate Among Patients With Locally Advanced or Metastatic Sarcoma Treated With Talimogene Laherparepvec in Combination With Pembrolizumab: A Phase 2 Clinical Trial

Importance

Patients with advanced sarcoma have limited treatment options. Talimogene laherparepvec (T-VEC) has been shown to increase tumor-specific immune activation via augmenting antigen presentation and T-cell priming.

Objective

To examine whether T-VEC in combination with pembrolizumab is associated with increased tumor-infiltrating lymphocyte infiltration and programmed death-ligand 1 expression and thus with increased antitumor activity in patients with locally advanced or metastatic sarcoma.

Design, Setting, and Participants

This open-label, single-institution phase 2 interventional trial of T-VEC plus pembrolizumab enrolled 20 patients with locally advanced or metastatic sarcoma between March 16 and December 4, 2017, for whom at least 1 standard systemic therapy had failed. The median duration of therapy was 16 weeks (range, 7-67 weeks). Reported analyses include data through December 14, 2018.

Intervention

Patients received pembrolizumab (200-mg flat dose) intravenously and T-VEC (first dose, ≤4 mL × 106 plaque-forming units [PFU]/mL; second and subsequent doses, ≤4 mL × 108 PFU/mL) injected into palpable tumor site(s) on day 1 of each 21-day cycle.

Main Outcomes and Measures

The primary end point was objective response rate (ORR; complete response and partial response) at 24 weeks determined by Response Evaluation Criteria In Solid Tumors (RECIST), version 1.1, criteria. Secondary end points included best ORR by immune-related RECIST criteria, progression-free survival rate at 24 weeks, overall survival, and safety.

Results

All 20 patients (12 women [60%]; median age, 63.5 years [range, 24-90 years]) were evaluable for response. The study met its primary end point of evaluating the best ORR at 24 weeks determined by RECIST, version 1.1, criteria; the best ORR was 30% (95% CI, 12%-54%; n = 6). The ORR overall was 35% (95% CI, 15%-59%; n = 7). The incidence of grade 3 treatment-related adverse events was low (4 patients [20%]). There were no grade 4 treatment-related adverse events or treatment-related deaths.

Conclusions and Relevance

In this phase 2 clinical trial, treatment with T-VEC plus pembrolizumab was associated with antitumor activity in advanced sarcoma across a range of sarcoma histologic subtypes, with a manageable safety profile. This combination therapy met its predefined primary study end point; further evaluation of T-VEC in combination with pembrolizumab for patients with select sarcoma subtypes is planned.

Trial Registration

ClinicalTrials.gov identifier: NCT03069378.

Long-term outcomes of pexidartinib in tenosynovial giant cell tumors

Background

The objective of this study was to report on the long‐term effects of pexidartinib on tenosynovial giant cell tumor (TGCT).

Methods

This was a pooled analysis encompassing 3 pexidartinib‐treated TGCT cohorts: 1) a phase 1 extension study (NCT01004861; 1000 mg/d; n = 39), 2) ENLIVEN patients randomized to pexidartinib (1000 mg/d for 2 weeks and then 800 mg/d; n = 61), and 3) ENLIVEN crossover patients (NCT02371369; 800 mg/d; n = 30). Eligible patients were 18 years old or older and had a histologically confirmed TGCT that was unresectable and symptomatic. Efficacy endpoints included the best overall response (complete or partial response) and the duration of response (DOR) by the Response Evaluation Criteria in Solid Tumors (RECIST) and the tumor volume score (TVS). The safety assessment included the frequency of treatment‐emergent adverse events (TEAEs) and hepatic laboratory abnormalities (aminotransferase elevations and mixed/cholestatic hepatotoxicity). The data cutoff was May 31, 2019.

Results

One hundred thirty patients with TGCT received pexidartinib (median treatment duration, 19 months; range, 1 to 76+ months); 54 (42%) remained on treatment at the end of the analysis (26 months after initial data cut of March 2017). The RECIST overall response rate (ORR) was 60%; the TVS ORR was 65%. The median times to response were 3.4 (RECIST) and 2.8 months (TVS), with 48 of the responding patients (62%) achieving a RECIST partial response by 6 months and with 72 (92%) doing so by 18 months. The median DOR was reached for TVS (46.8 months). Reported TEAEs were mostly low‐grade, with hair color changes being most frequent (75%). Most liver abnormalities (92%) were aminotransferase elevations; 4 patients (3%) experienced mixed/cholestatic hepatotoxicity (all within the first 2 months of treatment), which was reversible in all cases (recovery spanned 1‐7 months).

Conclusions

This study demonstrates the prolonged efficacy and tolerability of long‐term pexidartinib treatment for TGCT.

This analysis further illustrates that systemic therapy targeting the CSF1/CSF1R pathway is an effective therapeutic strategy in patients with tenosynovial giant cell tumor. Because of the limited availability of long‐term prospective data for tenosynovial giant cell tumor, these findings are encouraging and demonstrate the overall long‐term benefit of continued treatment with pexidartinib.

Clinical Outcome of Leiomyosarcomas With Somatic Alteration in Homologous Recombination Pathway Genes

PURPOSE

To detect alterations in DNA damage repair (DDR) genes, measure homologous recombination deficiency (HRD), and correlate these findings with clinical outcome in patients with leiomyosarcoma (LMS).

PATIENTS AND METHODS

Patients with LMS treated at Memorial Sloan Kettering (MSK) Cancer Center who consented to prospective targeted next-generation sequencing with MSK-IMPACT were screened for oncogenic somatic variants in one of 33 DDR genes; where feasible, an experimental HRD score was calculated from IMPACT data. Progression-free survival (PFS) and overall survival (OS) were estimated after stratifying patients by DDR gene alteration status and HRD score.

RESULTS

Of 211 patients with LMS, 20% had an oncogenic DDR gene alteration. Univariable analysis of PFS in 117 patients who received standard frontline chemotherapy in the metastatic setting found that an altered homologous recombination pathway gene was significantly associated with shorter PFS (hazard ratio [HR], 1.79; 95% CI, 1.04 to 3.07; P = .035). Non-BRCA homologous recombination gene alteration was associated with shorter PFS (HR, 2.61; 95% CI, 1.35 to 5.04; P = .004) compared with BRCA-altered and wild-type homologous recombination genes. Univariable analysis of OS from diagnosis in the entire cohort of 211 patients found that age, tumor size, number of metastatic sites, localized disease, and non-BRCA homologous recombination gene alteration were significantly associated with OS. On multivariable analysis, non-BRCA homologous recombination pathway gene alteration remained significant (HR, 4.91; 95% CI, 2.47 to 9.76; P < .001). High HRD score was not associated with a different PFS or OS.

CONCLUSION

Patients with LMS with homologous recombination pathway gene alterations have poor clinical outcomes, particularly those with non-BRCA gene alterations. HRD score calculated from a targeted exome panel did not discern disparate clinical outcomes.

Diagnosis and management of tropomyosin receptor kinase (TRK) fusion sarcomas: expert recommendations from the World Sarcoma Network

Sarcomas are a heterogeneous group of malignancies with mesenchymal lineage differentiation. The discovery of neurotrophic tyrosine receptor kinase (NTRK) gene fusions as tissue-agnostic oncogenic drivers has led to new personalized therapies for a subset of patients with sarcoma in the form of tropomyosin receptor kinase (TRK) inhibitors. NTRK gene rearrangements and fusion transcripts can be detected with different molecular pathology techniques, while TRK protein expression can be demonstrated with immunohistochemistry. The rarity and diagnostic complexity of NTRK gene fusions raise a number of questions and challenges for clinicians. To address these challenges, the World Sarcoma Network convened two meetings of expert adult oncologists and pathologists and subsequently developed this article to provide practical guidance on the management of patients with sarcoma harboring NTRK gene fusions. We propose a diagnostic strategy that considers disease stage and histologic and molecular subtypes to facilitate routine testing for TRK expression and subsequent testing for NTRK gene fusions.

Population Pharmacokinetic Analysis of Pexidartinib in Healthy Subjects and Patients With Tenosynovial Giant Cell Tumor or Other Solid Tumors

Pexidartinib is a kinase inhibitor that induces tumor response and improvements in symptoms and functional outcomes in adult patients with symptomatic tenosynovial giant cell tumor (TGCT). A population pharmacokinetic (PK) model for pexidartinib and its metabolite, ZAAD, was developed, and effects of demographic and clinical factors on the PK of pexidartinib and ZAAD were estimated. The analysis included pooled data from 7 studies in healthy volunteers (N = 159) and 2 studies in patients with TGCT or other solid tumors (N = 216). A structural 2‐compartment model with sequential zero‐ and first‐order absorption and lag time, and linear elimination from the central compartment adequately described pexidartinib and ZAAD PKs. Clearance of pexidartinib was estimated at 5.83 L/h in a typical patient with reference covariates (male, non‐Asian, weight = 80 kg, creatinine clearance ≥90 mL/min, aspartate aminotransferase ≤80 U/L, and total bilirubin ≤20.5 μmol/L). In the covariate analysis, Asians and healthy subjects had modestly lower pexidartinib exposure (21% decrease each) in terms of steady‐state area under the curve values from 0 to 24 hours (AUC_0‐24,ss). Effects of body weight, sex, and hepatic function parameters on pexidartinib AUC_0‐24,ss were generally <20%. Patients with TGCT with mild renal impairment were predicted to have approximately 23% higher AUC_0‐24,ss than those with normal renal function. The effects of covariates on ZAAD exposure were similar to those on pexidartinib. These results indicate small and generally clinically nonmeaningful effects of patient demographic and clinical characteristics on pexidartinib and ZAAD PK profiles.

The epigenomics of sarcoma

Epigenetic regulation is critical to physiological control of development, cell fate, cell proliferation, genomic integrity and, fundamentally, transcriptional regulation. This epigenetic control occurs at multiple levels including through DNA methylation, histone modification, nucleosome remodelling and modulation of the 3D chromatin structure. Alterations in genes that encode chromatin regulators are common among mesenchymal neoplasms, a collection of more than 160 tumour types including over 60 malignant variants (sarcomas) that have unique and varied genetic, biological and clinical characteristics. Herein, we review those sarcomas in which chromatin pathway alterations drive disease biology. Specifically, we emphasize examples of dysregulation of each level of epigenetic control though mechanisms that include alterations in metabolic enzymes that regulate DNA methylation and histone post-translational modifications, mutations in histone genes, subunit loss or fusions in chromatin remodelling and modifying complexes, and disruption of higher-order chromatin structure. Epigenetic mechanisms of tumorigenesis have been implicated in mesenchymal tumours ranging from chondroblastoma and giant cell tumour of bone to chondrosarcoma, malignant peripheral nerve sheath tumour, synovial sarcoma, epithelioid sarcoma and Ewing sarcoma - all diseases that present in a younger patient population than most cancers. Finally, we review current and potential future approaches for the development of sarcoma therapies based on this emerging understanding of chromatin dysregulation.

Abstract 2020: Identification of abnormal CSF1 transcripts in tenosynovial giant cell tumors and dose-dependent increase in plasma CSF1 levels in response to pexidartinib treatment

Background: Tenosynovial giant cell tumors (TGCTs) are characterized by rearrangements of the colony-stimulating factor 1 (CSF1) gene. Dysregulated CSF1 may attract CSF1 receptor (CSF1R)-bearing mononuclear cells that form the bulk of the tumor. CSF1R inhibitors including pexidartinib have been developed and have proven to be effective therapies.

Methods: Formalin-fixed paraffin-embedded (FFPE) TGCT specimens from the phase 1 first-in-human study of pexidartinib (NCT01004861) were analyzed using a custom sequencing assay to detect CSF1 genetic alterations. The ArcherDX RNA panel (ArcherDX, Inc., Boulder, CO) consisted of 33 gene-specific primer sets specifically designed to target CSF1, including at least 1 primer set to target each exon/exon boundary as well as primer sets to tile the 3′-untranslated region (3′UTR). Plasma samples from 5 phase 1 trials of pexidartinib across multiple tumor types (NCT02777710, NCT01217229, NCT01525602, NCT01790503, NCT02452424) were assayed for CSF1 protein by solid-phase ELISA (Quantikine® Human MCSF, R&D Systems, Inc., Minneapolis, MN) at baseline and following pexidartinib (200-1200 mg).

Results: FFPE TGCT specimens (N=25) were successfully isolated, prepared into libraries, and sequenced; 8 showed evidence of gene rearrangements at the junction of CSF1 exons 5/6, and 15 showed alterations of the CSF1 3′UTR (n=23). All 25 TGCT libraries had higher CSF1 expression, with 24 exceeding 2-fold of the RNA control library. The plasma samples from 132 patients were analyzed for CSF1 protein. Pexidartinib treatment (200-1200 mg) led to a dose-dependent increase in plasma CSF1 by day 8, 15, or 29. Significant (&gt;4-fold) CSF1 elevation was observed at 600 mg or higher doses.

Discussion: All 25 analyzed TGCT study patients had tumor tissue with elevated CSF1 ligand transcripts, and 23 had CSF1 genomic alterations identified, thus confirming the TGCT etiology for which pexidartinib therapy was recently approved. The initial discovery of gross chromosomal aberrations involving the CSF1 locus used break-apart FISH probes (West et al. Proc Natl Acad Sci USA. 2006;103:690-695). Details of the CSF1 gene aberrations were obtained here using a sequencing assay suitable for FFPE specimens having partially degraded RNA. Abnormal CSF1 transcripts identified in our study are similar to those published by others (Ho et al. Genes Chromosomes Cancer. 2019[Epub]; Tsuda et al. Int J Cancer. 2019;145:3276-3284) after completion of our work, including both predicted fusion proteins and loss of 3′UTR microRNA negative regulatory sites. Increased plasma CSF1 is a useful pharmacodynamics marker of CSF1R inhibition. One potential mechanism for CSF1 plasma elevations could be the inhibition of liver macrophages, known to express CSF1R and thought to play an essential role in the normal clearance of CSF1 from circulation.

Citation Format: Paul Severson, Brian L. West, William D. Tap, Zev A. Wainberg, Sandra Tong-Starksen, Henry H. Hsu, Chao Zhang. Identification of abnormal CSF1 transcripts in tenosynovial giant cell tumors and dose-dependent increase in plasma CSF1 levels in response to pexidartinib treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2020.

HLA Genotyping in Synovial Sarcoma: Identifying HLA-A*02 and Its Association with Clinical Outcome

PURPOSE

To determine if a targeted exome panel utilizing matched normal DNA can accurately detect germline and somatic HLA genes in patients with synovial sarcoma (SS) and whether select HLA-A*02 genotypes are prognostic or predictive of outcome in metastatic SS.

EXPERIMENTAL DESIGN

Patients with metastatic SS consented to HLA typing by a Clinical Laboratory Improvement Amendments (CLIA)-certified test to determine eligibility for a clinical trial of NY-ESO-1-specific engineered T cells restricted to carriers of HLA-A*02:01, -A*02:05, or -A*02:06 (HLA-A*02 eligible). HLA genotype was determined from Memorial Sloan Kettering Integrated Molecular Profiling of Actionable Cancer Targets (MSK-IMPACT), where feasible, and somatic loss of heterozygosity (LOH) in HLA alleles was identified. Overall survival (OS) was estimated and stratified by HLA-A*02 eligibility.

RESULTS

A total of 23 patients had HLA genotyping by a CLIA-certified lab and MSK-IMPACT. Ninety percent (108/110) of the sequenced alleles were concordant between IMPACT and the outside lab. LOH of HLA genes was detected in three tumors, one had loss of HLA-A*02:01. In total, 66 patients were screened for T-cell therapy and 20 (30%) were HLA-A*02 eligible on outside testing. Univariate analysis of OS from the time of metastasis found HLA-A*02 eligibility was marginally associated with shorter OS [HR = 1.95; 95% confidence interval (CI), 0.995-3.813; P = 0.052]. On multivariate analysis, older age and larger tumor size, but not HLA-A*02 eligibility, were significantly associated with decreased OS. HLA-A*02 eligibility did not impact OS after chemotherapy or pazopanib in the metastatic setting.

CONCLUSIONS

Targeted gene panels like MSK-IMPACT may accurately report HLA type and identify loss of somatic HLA alleles. In a multivariable model, HLA-A*02 eligibility was not significantly associated with OS in patients with metastatic SS.

Avapritinib in advanced PDGFRA D842V-mutant gastrointestinal stromal tumour (NAVIGATOR): a multicentre, open-label, phase 1 trial

BACKGROUND

Targeting of KIT and PDGFRA with imatinib revolutionised treatment in gastrointestinal stromal tumour; however, PDGFRA Asp842Val (D842V)-mutated gastrointestinal stromal tumour is highly resistant to tyrosine kinase inhibitors. We aimed to assess the safety, tolerability, and antitumour activity of avapritinib, a novel KIT and PDGFRA inhibitor that potently inhibits PDGFRA D842V, in patients with advanced gastrointestinal stromal tumours, including patients with KIT and PDGFRA D842V-mutant gastrointestinal stromal tumours (NAVIGATOR).

METHODS

NAVIGATOR is a two-part, open-label, dose-escalation and dose-expansion, phase 1 study done at 17 sites across nine countries (Belgium, France, Germany, Poland, Netherlands, South Korea, Spain, the UK, and the USA). Patients aged 18 years or older, with an Eastern Cooperative Oncology Group performance status of 2 or less, and with adequate end-organ function were eligible to participate. The dose-escalation part of the study included patients with unresectable gastrointestinal stromal tumours. The dose-expansion part of the study included patients with an unresectable PDGFRA D842V-mutant gastrointestinal stromal tumour regardless of previous therapy or gastrointestinal stromal tumour with other mutations that either progressed on imatinib and one or more tyrosine kinase inhibitor, or only received imatinib previously. On the basis of enrolment trends, ongoing review of study data, and evolving knowledge regarding the gastrointestinal stromal tumour treatment paradigm, it was decided by the sponsor's medical director together with the investigators that patients with PDGFRA D842V mutations would be analysed separately; the results from this group of patients is reported in this Article. Oral avapritinib was administered once daily in the dose-escalation part (starting dose of 30 mg, with increasing dose levels once daily in continuous 28-day cycles until the maximum tolerated dose or recommended phase 2 dose was determined; in the dose-expansion part, the starting dose was the maximum tolerated dose from the dose-escalation part). Primary endpoints were maximum tolerated dose, recommended phase 2 dose, and safety in the dose-escalation part, and overall response and safety in the dose-expansion part. Safety was assessed in all patients from the dose-escalation part and all patients with PDGFRA D842V-mutant gastrointestinal stromal tumour in the dose-expansion part, and activity was assessed in all patients with PDGFRA D842V-mutant gastrointestinal stromal tumour who received avapritinib and who had at least one target lesion and at least one post-baseline disease assessment by central radiology. This study is registered with ClinicalTrials.gov, NCT02508532.

FINDINGS

Between Oct 26, 2015, and Nov 16, 2018 (data cutoff), 46 patients were enrolled in the dose-escalation part, including 20 patients with a PDGFRA D842V-mutant gastrointestinal stromal tumour, and 36 patients with a PDGFRA D842V-mutant gastrointestinal stromal tumour were enrolled in the dose-expansion part. At data cutoff (Nov 16, 2018), 38 (46%) of 82 patients in the safety population (median follow-up of 19·1 months [IQR 9·2-25·5]) and 37 (66%) of the 56 patients in the PDGFRA D842V population (median follow-up of 15·9 months [IQR 9·2-24·9]) remained on treatment. The maximum tolerated dose was 400 mg, and the recommended phase 2 dose was 300 mg. In the safety population (patients with PDGFRA D842V-mutant gastrointestinal stromal tumour from the dose-escalation and dose-expansion parts, all doses), treatment-related grade 3-4 events occurred in 47 (57%) of 82 patients, the most common being anaemia (14 [17%]); there were no treatment-related deaths. In the PDGFRA D842V-mutant population, 49 (88%; 95% CI 76-95) of 56 patients had an overall response, with five (9%) complete responses and 44 (79%) partial responses. No dose-limiting toxicities were observed at doses of 30-400 mg per day. At 600 mg, two patients had dose-limiting toxicities (grade 2 hypertension, dermatitis acneiform, and memory impairment in patient 1, and grade 2 hyperbilirubinaemia in patient 2).

INTERPRETATION

Avapritinib has a manageable safety profile and has preliminary antitumour activity in patients with advanced PDGFRA D842V-mutant gastrointestinal stromal tumours.

FUNDING

Blueprint Medicines.

The clinical heterogeneity of round cell sarcomas with EWSR1/FUS gene fusions: Impact of gene fusion type on clinical features and outcome

The genetic hallmark of classic Ewing sarcoma is a recurrent fusion between EWSR1 and FUS gene with a member of the ETS transcription factor family. In contrast, tumors with non-ETS gene partners have been designated until recently "Ewing-like sarcoma," as a provisional molecular entity, as their clinical and pathologic features were still evolving. However, this group was reclassified as "round cell sarcoma with EWSR1-non-ETS fusions" in the latest 2020 WHO classification. Moreover, round cell sarcomas with either CIC or BCOR gene abnormalities, initially classified under Ewing family of tumors, are now regarded as stand-alone pathologic entities based on their distinct features. In this study we investigated the clinical characteristics of 226 confirmed Ewing sarcoma patients (EWSR1-FLI1 [n = 176], EWSR1/FUS-ERG [n = 35], EWSR1/FUS-FEV [n = 12], and EWSR1-ETV1/4 [n = 3]) and 14 round cell sarcoma patients with EWSR1-non-ETS fusion (EWSR1/FUS-NFATC2 [n = 10], EWSR1-PATZ1 [n = 3], and EWSR1-VEZF1 [n = 1]). The impact on overall survival (OS) was assessed in 90 patients with available follow-up, treated between 2011 and 2018. Patients with fusions involving FEV and NFATC2 genes showed an older median age at diagnosis, compared to those with EWSR1-FLI1 (P = .005), while extraskeletal location was more common in tumors with noncanonical EWSR1-FLI1 fusions (P = .001). Axial and pelvic primary sites were more common in patients with EWSR1-FLI1 (72%), while tumors with NFATC2 fusions were more frequent in the limb (78%, P = .006). The 3-year OS in patients with EWSR1-FLI1 was 91%, compared to only 60% in patients with alternative fusions (P = .037); the latter group showing a higher rate of metastases at presentation. However, this OS difference was not significant in patients with localized tumor (P = .585). Our study demonstrates significant correlations between fusion subtype and age at presentation, primary tumor sites, and OS, in both conventional Ewing sarcoma and round cell sarcoma with EWSR1-non ETS fusions patients. Larger studies are needed to determine survival differences in localized tumors.

Association of immune-related adverse events (irAEs) with improved clinical outcome in sarcoma patients treated with immune checkpoint blockade (ICB)

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Background: IrAEs are associated with improved clinical outcomes after treatment with ICB in select epithelial malignancies. We hypothesized that sarcoma patients (pts) treated with ICB who developed an irAE would have improved outcomes compared to pts who had no irAE. Methods: Adverse events (AEs) from 3 sarcoma-specific ICB trials (nivolumab plus NKTR-214, pembrolizumab plus epacadostat, and pembrolizumab plus T-VEC) were reviewed. AEs probably or definitely related to ICB were classified as immune- or non-immune-related by the principal investigator. Endpoints of interest included best overall response (BOR) by RECIST 1.1 (complete response [CR]/partial response [PR]), durable clinical benefit (DCB; CR/PR/stable disease [SD] ≥ 16 weeks), and progression-free survival (PFS). Outcomes were stratified by the presence or absence of ≥ 1 irAE of any grade and by grade 1-2, grade 3-4, or no irAE (three-category comparison). Results: A total of 124 pts received ICB on these studies. Median pt age was 56 (range: 13-90); 53% were male; all but one pt had a performance status of ≤ 1. BOR was PR in 12 pts, SD in 41, and PD in 69. 2 pts were not evaluable. 40 pts (32%) had ≥ 1 irAE of any grade, 6 of whom had a grade 3-4 irAE. The most common irAEs (≥ 5% of pts) were rash (15%), arthralgia (11%), myalgia (9%), pruritis (8%), and hypothyroidism (6%). The proportion of pts with a CR/PR was higher in pts with than without an irAE (18% vs. 6%, respectively; P = 0.058). A significantly higher proportion of pts with an irAE had DCB compared to those without (53% and 29%, respectively; P = 0.017). The median PFS of pts with an irAE was 16.6 months compared to 10.6 in those without (P = 0.013). The proportion of pts with a grade 3-4 irAE and a CR/PR was highest (33%) compared to pts with grade 1-2 (15%) or no irAE (6%) (P = 0.048). More pts with grade 3-4 irAE achieved DCB (67%) than grade 1-2 (50%) or no irAE (29%) (P = 0.027). Median PFS was 22.6, 15, and 10.6 weeks in the grade 3-4, grade 1-2, and no irAE groups, respectively (P = 0.047). Conclusions: Approximately one-third of advanced sarcoma pts with ICB-based immunotherapy developed an irAE. As reported previously in select carcinomas, sarcoma pts with irAEs were more likely to have clinical benefit than those without irAEs. Further research is needed to understand the mechanism behind this association and to validate these findings prospectively.

Phase I Study of the Mutant IDH1 Inhibitor Ivosidenib: Safety and Clinical Activity in Patients With Advanced Chondrosarcoma

PURPOSE

Surgery is the primary therapy for localized chondrosarcoma; for locally advanced and/or metastatic disease, no known effective systemic therapy exists. Mutations in the isocitrate dehydrogenase 1/2 (IDH1/2) enzymes occur in up to 65% of chondrosarcomas, resulting in accumulation of the oncometabolite D-2-hydroxyglutarate (2-HG). Ivosidenib (AG-120) is a selective inhibitor of mutant IDH1 approved in the United States for specific cases of acute myeloid leukemia. We report outcomes of patients with advanced chondrosarcoma in an ongoing study exploring ivosidenib treatment.

PATIENTS AND METHODS

This phase I multicenter open-label dose-escalation and expansion study of ivosidenib monotherapy enrolled patients with mutant IDH1 advanced solid tumors, including chondrosarcoma. Ivosidenib was administered orally (100 mg twice daily to 1,200 mg once daily) in continuous 28-day cycles. Responses were assessed every other cycle using RECIST (version 1.1).

RESULTS

Twenty-one patients (escalation, n = 12; expansion, n = 9) with advanced chondrosarcoma received ivosidenib (women, n = 8; median age, 55 years; range, 30-88 years; 11 had received prior systemic therapy). Treatment-emergent adverse events (AEs) were mostly grade 1 or 2. Twelve patients experienced grade ≥ 3 AEs; only one event was judged treatment related (hypophosphatemia, n = 1). Plasma 2-HG levels decreased substantially in all patients (range, 14%-94.2%), to levels seen in healthy individuals. Median progression-free survival (PFS) was 5.6 months (95% CI, 1.9 to 7.4 months); the PFS rate at 6 months was 39.5%. Eleven (52%) of 21 patients experienced stable disease.

CONCLUSION

In patients with chondrosarcoma, ivosidenib showed minimal toxicity, substantial 2-HG reduction, and durable disease control. Future studies of ivosidenib monotherapy or rational combination approaches should be considered in patients with advanced mutant IDH1 chondrosarcoma.

A randomized phase II study of MLN0128 (M) versus pazopanib (P) in patients (pt) with advanced sarcoma (Alliance A091304)

11562

Background: Soft tissue sarcoma (STS) is a heterogeneous malignancy of connective tissue. Although mTOR is implicated in STS pathogenesis, clinical activity from mTORC1 inhibitors is modest. M, a potent selective mTORC1/mTORC2 inhibitor, was more effective in STS preclinical models than inhibitors of mTORC1, IGF1R and mTORC1+IGF1R, owing to more complete suppression of PI3K/AKT/mTOR and abrogation of feedback AKT activation. P, an oral multikinase inhibitor, is approved for non-adipocytic STS and often used after progression (PD) on chemotherapy. In phase 1, the RP2D of M was 30 mg weekly. A091304 was to evaluate M as a novel targeted therapy for STS. Methods: In A091304, pts were randomized 1:1 to M 30 mg weekly or P 800 mg daily. Eligibility required Eastern Cooperative Oncology Group PS ≤ 1, progression on ≥ 1 prior chemotherapy and specific STS subtypes (cohort 1: UPS; 2: LMS; 3: MPNST, SS). Crossover to M was allowed after PD on P. 1° endpoint was progression-free survival (PFS). Assuming median PFS of P was 4.6 months (mo), 98 pts yielded 80% power to detect a hazard ratio of 0.66 favoring M [1-sided test, alpha = 0.15] and including 1 planned futility analysis. 2° endpoints were response rate, clinical benefit rate (CBR) at 4 mo and safety. After 4 of the first 12 pts randomized to P experienced ≥ grade (gr) 3 toxicity, the study was amended to begin at P 400 mg, allowing titration to 800 per investigator discretion. Results: After protocol amendment, 114 pt underwent randomization (M: 56, P: 58), and 111 initiated treatment. Median PFS was 2 mo for M and 2.1 mo for P (HR = 1.47; 1-sided 85% upper confidence boundary = 1.85), with 2 partial responses in each arm. CBR was 5.4% for M and 13.8% for P. Median OS was 10.7 mo for M and 13.9 mo for P (HR = 1.41; 95% CI 0.80-2.49). 26/43 pt with PD on P crossed over to M. Median PFS after crossover was 1.8 mo (95% CI 1.5-3.5). Gr 3 drug-related adverse events (AEs) occurred in 36% on M and 41% on P; gr 4 toxicity was rare. AEs were consistent with known effects of M and P. Conclusions: P at 400 mg daily (allowing escalation to 800 mg per investigator discretion) demonstrated a shorter PFS as compared prior randomized studies with P. Despite this, M failed to demonstrate superior clinical activity as compared to P at the interim analysis. Further work will examine activity within histology-specific cohorts and evaluate available tissue samples for evidence of pharmacodynamic activity. Support: U10CA180821, U10CA180882, U10CA180888, UG1CA233324 (SWOG); https://acknowledgments.alliancefound.org . Clinical trial information: NCT02601209 .

HLA genotyping in synovial sarcoma: Identifying HLA-A*02 and its association with clinical outcome

e23560

Background: Patients (pts) with synovial sarcoma (SS) and an HLA-A*02 genotype whose tumors express NY-ESO-1 may be eligible for clinical trials of adoptive T cell therapy. We reasoned that a next generation tumor sequencing platform utilizing matched normal DNA (MSK-IMPACT) could accurately identify HLA genotype. Although HLA-A*02 is necessary for some adoptive T cell therapies, the prognosis of this genotype on clinical outcome has not been described in SS. Methods: Pts with metastatic SS who consented to screen for a clinical trial of engineered T cells had high-resolution HLA genotyping performed with a Clinical Laboratory Improvement Amendments (CLIA)-certified test. Where feasible, HLA genotype and loss-of-heterozygosity (LOH) of HLA alleles were determined from IMPACT samples. Overall survival (OS) was estimated in three overlapping cohorts and stratified by HLA-A*02 status: pts treated with anthracyclines or alkylators in the first line, pazopanib in the second line or beyond, and all pts from time of metastasis. Results: 66 pts with SS were screened, but not treated with T cells; 30% (n = 20) were HLA-A*02-positive on a CLIA-certified outside test. 23 pts had HLA genotyping both by IMPACT and an outside laboratory, 22 (96%) of whom had concordant results. 3 pts had LOH of at least 1 HLA allele, including one with LOH of HLA*02:01 in the primary tumor. Among pts treated chemotherapy (n = 36) or pazopanib (n = 37), OS did not significantly differ between HLA-A*02-positive or negative pts. Univariable analyses of OS from the time of metastasis in the whole cohort identified primary tumor size and time to metastasis as variables significantly associated with outcome (hazard ratio (HR) 1.2, 95% confidence interval (CI) 1.123 – 1.345 [P < 0.001] and HR 0.99, 95% CI 0.976 – 0.999 [P = 0.032], respectively). HLA-A*02-positive status and age did not reach the significance threshold (HR 1.95, 95% CI 0.995 – 3.813 [P = 0.052] and HR 1.021, 95% CI 0.999 – 1.044 [P = 0.061], respectively). Multivariable analysis found older age and larger tumor size were independently associated with significantly shorter OS (HR 1.03, 95% CI 1.002 – 1.049 [P = 0.037] and HR 1.2, 95% CI 1.127 – 1.37 [P < 0.001], respectively). Conclusions: Targeted exome panels like IMPACT that utilize matched tumor-normal DNA may accurately identify HLA genotype. Detection of LOH at HLA loci may identify a subgroup of pts who would be refractory to treatment with HLA-A*02-restricted engineered T cells. HLA-A*02 status was not associated with a statistically significant survival difference in pts with metastatic SS.

A phase II study of MEK162 (binimetinib [BINI]) in combination with imatinib in patients with untreated advanced gastrointestinal stromal tumor (GIST)

11508

Background: ETV1 and KIT are lineage-specific master transcriptional and signaling survival factors in GIST. In preclinical models, dual lineage targeting of ETV1 by MEK inhibition with BINI and KIT by imatinib are synergistic in suppressing GIST tumorigenesis and progression. This single-arm phase II study is designed to test the efficacy of the BINI+imatinib as a first-line treatment in patients (pts) with advanced GIST. Methods: Adult pts with untreated advanced GIST received imatinib (400mg daily) plus BINI (30mg twice daily), 28-day cycles. The primary endpoint (EP) was RECIST1.1 objective response rate (ORR) (complete response [CR]+partial response [PR]). The study was designed to detect a 20% improvement in the ORR of imatinib alone (unacceptable rate of 45%; acceptable rate of 65%). A sample size of 44 patients was required, using an exact binomial test, one-sided type I error of 0.08 and type II error of 0.1. Confirmed PR in > 24 pts would be considered positive. Secondary EPs included RR by Choi and EORTC criteria, resectability conversion rate (RCR), progression free survival (PFS), overall survival (OS) and long-term AEs. Correlatives included characterization of tumor genomics by MSK-IMPACT, cfDNA by MSK-ACCESS, ETV1 protein levels and transcriptomes and signaling inhibition. Results: At data cutoff of Jan 31, 2020, 38/39 pts with advanced GIST of all genotypes, including 3 KIT/PDGFRA-wild type GIST pts, were evaluable for primary EP. Median age 60 (range 29-78), 29% female. 26/38 pts with confirmed PR; Best ORR was 68.4% (two-sided 95% CI, 51-83%; one-sided 90% CI, 57-100%). 8/9 pts became resectable after treatment; RCR was 88.9% (95% CI, 52-100%). 13 pts remain on trial (2-159 weeks [wks]). 9 pts discontinued trial due to disease progression (11-159 wks); one pt progressed within 3 months, indicating primary resistance. Grade 3/4 toxicity included CPK elevation (asymptomatic, 61%), neutrophil decrease (11%), maculopapular rash (8%), anemia (8%). No unexpected toxicities observed. Correlation of outcome with MSK-IMPACT, MSK-Access and paired tumor biopsies will be presented. Conclusions: This study met its primary endpoint. BINI plus imatinib is highly effective in treatment-naive advanced GIST, with expected and manageable long-term treatment-associated toxicities. The combination strategy warrants further evaluation in direct comparison with imatinib in the frontline treatment of GIST. Clinical trial information: NCT01991379 .

Defining patient-elicited concepts unique to adolescents and young adults with cancer

12118

Background: Adolescents and young adults (AYAs) require a multidisciplinary approach to cancer care due to complex biopsychosocial variables and varied developmental maturity. Currently, age and diagnosis determine referral to pediatric or adult oncology with differing care paradigms and service utilization. These issues, in conjunction with differences in tumor biology and lower accrual to clinical trials, have contributed to marginal improvements in outcomes for AYAs. Compounding this dilemma is a lack of validated patient-reported outcome measures (PROs) for AYAs. Tracking standardized PROs longitudinally is a crucial step in understanding psychosocial variables, identifying tailored needs, improving outcomes and standardizing care. However, developing a PRO tool for AYAs first requires identifying AYA-unique domains. Methods: Three, 90-minute focus groups were conducted with AYAs treated at Memorial Sloan Kettering in the context of 1) pediatric oncology, 2) medical oncology, and 3) either service. Topics explored included: experiences of cancer care as an AYA; physical, social and emotional concerns; and information needs, including appropriateness, timing, and depth of information. Thematic content analysis of transcripts was performed by four interdisciplinary coders in weekly iterative consensus rounds. Phase one consisted of identification of key domains to guide line-by-line coding with NVivo software. Phase two consisted of independent review and categorization of codes, followed by three successive consensus meetings to identify distinct themes. Results: A mean of 6 patients (range 5-7) participated in each of the 3 groups; the total sample (n = 17) included 9 males and 8 females, ages 19-35 years (median 26). Four AYA-unique themes were identified: 1. AYAs have an uncertain sense of the future and desire more engagement in conversations pertaining to survivorship, long-term effects and transition to outpatient life. 2. Cancer as an AYA is a socially-isolating experience, prompting a strong desire to connect with peers during and post-treatment. 3. AYAs want control over who can be present during discussions with their care team as the presence of loved ones can impede or facilitate communication. 4. AYAs may be living far away from loved ones during treatment and lack supports needed to help them navigate treatment and daily life. Conclusions: Concept elicitation via focus groups identified novel themes related to survivorship, isolation, communication and social support, which can inform development of AYA-specific PROs.