Stereotactic Radiation for Ultra-Central Non-Small Cell Lung Cancer: A Safety and Efficacy Trial (SUNSET)

INTRODUCTION

The use of stereotactic body radiotherapy (SBRT) for tumors in close proximity to the central mediastinal structures has been associated with a high risk of toxicity. This study (BLINDED FOR REVIEW) aimed to determine the maximally tolerated dose (MTD) of SBRT for ultra-central (UC) non-small cell lung carcinoma (NSCLC), using a time-to-event continual reassessment methodology (TITE-CRM).

METHODS

Patients with T1-3N0M0 (≤ 6 cm) NSCLC were eligible. The MTD was defined as the dose of radiotherapy associated with a ≤ 30% rate of grade (G) 3-5 pre-specified treatment-related toxicity occurring within 2 years of treatment. The starting dose level was 60 Gy in 8 daily fractions. The dose-maximum hotspot was limited to 120% and within the planning tumor volume (PTV); tumors with endobronchial invasion were excluded. This primary analysis occurred two years after completion of accrual.

RESULTS

Between March 2018 and April 2021, 30 patients were enrolled at 5 institutions. The median age was 73 years (range: 65-87) and 17 (57%) were female. PTV was abutting proximal bronchial tree in 19 (63%), esophagus 5 (17%), pulmonary vein 1 (3.3%) and pulmonary artery 14 (47%). All patients received 60 Gy in 8 fractions. The median follow-up was 37 months (range: 8.9-51). Two patients (6.7%) experienced G3-5 adverse events related to treatment: 1 patient with G3 dyspnea and 1 G5 pneumonia; the latter had CT findings consistent with a background of interstitial lung disease. Three-year overall survival was 72.5% (95% confidence interval [CI]: 52.3-85.3%), progression-free survival 66.1% (95% CI: 46.1-80.2%), local control 89.6% (95% CI: 71.2-96.5%), regional control 96.4% (95% CI: 77.2-99.5%) and distant control 85.9% (95% CI: 66.7-94.5%). Quality of life scores declined numerically over time, but the decreases were not clinically or statistically significant.

CONCLUSIONS

60 Gy in 8 fractions, planned and delivered with only a moderate hotspot, has a favorable adverse event rate within the pre-specified acceptability criteria, and results in excellent control for UC tumors.

CRISPR Screen of Druggable Targets in Small Cell Lung Cancer Identified ATM Inhibitor (AZD1390) as a Radiosensitizer

PURPOSE

Small cell lung cancer (SCLC) is an aggressive and lethal form of lung cancer and the overall 5-year survival (OS) for patients is a dismal 7%. Radiation therapy (RT) provides some benefit for selected patients with SCLC but could be improved with radiosensitizing agents. In this study, we identified novel radiosensitizers for SCLC by a CRISPR-Cas9 screen and evaluated the efficacy of ATM inhibitor AZD1390 as a radiosensitizer of SCLC.

METHODS AND MATERIALS

We transduced the SCLC cell line SBC5 with a custom CRISPR sgRNA library focused on druggable gene targets and treated cells with RT. Cells collected at multiple timepoints were subjected to next-generation sequencing. We determined radiosensitization both in vitro with cell lines assessed by short-term viability and clonogenic assays, and in vivo mouse models by tumor growth delay. Pharmacodynamic effects of AZD1390 were quantified by ATM-Ser1981 phosphorylation, and RT-induced DNA damage by comet assay.

RESULTS

Using a CRISPR dropout screen, we identified multiple radiosensitizing genes for SCLC at various timepoints with ATM as a top determinant gene for radiosensitivity. Validation by ATM knockout (KO) demonstrated increased radiosensitivity by short-term viability assay (dose modification factor [DMF]50 = 3.25-3.73 in SBC5 ATM-KO) and clonogenic assays (DMF37 1.25-1.65 in SBC5 ATM-KO). ATM inhibition by AZD1390 effectively abrogated ATM Ser1981 phosphorylation in SCLC cell lines and increased RT-induced DNA damage. AZD1390 synergistically increased the radiosensitivity of SCLC cell lines (cell viability assay: SBC5 DMF37 = 2.19, SHP77 DMF37 = 1.56, H446 DMF37 = 3.27, KP1 DMF37 = 1.65 at 100nM; clonogenic assay: SBC5 DMF37 = 4.23, H1048 DMF37 = 1.91), and in vivo murine syngeneic, KP1, and patient-derived xenograft (PDX) models, JHU-LX108 and JHU-LX33.

CONCLUSIONS

In this study, we demonstrated that genetically and pharmacologically (AZD1390) inhibiting ATM markedly enhanced RT against SCLC, providing a novel pharmacologically tractable radiosensitizing strategy for patients with SCLC.

Stereotactic Radiation Therapy in Early Non-Small Cell Lung Cancer and Interstitial Lung Disease: A Nonrandomized Clinical Trial

Importance

Patients with interstitial lung disease (ILD) and early-stage non-small cell lung cancer (NSCLC) have been reported to be at high risk of toxic effects after stereotactic ablative radiotherapy (SABR), but for many patients, there are limited alternative treatment options.

Objective

To prospectively assess the benefits and toxic effects of SABR in this patient population.

Design, Setting, and Participants

This prospective cohort study was conducted at 6 academic radiation oncology institutions, 5 in Canada and 1 in Scotland, with accrual between March 7, 2019, and January 12, 2022. Patients aged 18 years or older with fibrotic ILD and a diagnosis of T1-2N0 NSCLC who were not candidates for surgical resection were enrolled.

Intervention

Patients were treated with SABR to a dose of 50 Gy in 5 fractions every other day.

Main Outcomes and Measures

The study prespecified that SABR would be considered worthwhile if median overall survival-the primary end point-was longer than 1 year, with a grade 3 to 4 risk of toxic effects less than 35% and a grade 5 risk of toxic effects less than 15%. Secondary end points included toxic effects, progression-free survival (PFS), local control (LC), quality-of-life outcomes, and changes in pulmonary function. Intention-to-treat analysis was conducted.

Results

Thirty-nine patients enrolled and received SABR. Median age was 78 (IQR, 67-83) years and 59% (n = 23) were male. At baseline, 70% (26 of 37) of patients reported dyspnea, median forced expiratory volume in first second of expiration was 80% (IQR, 66%-90%) predicted, median forced vital capacity was 84% (IQR, 69%-94%) predicted, and median diffusion capacity of the lung for carbon monoxide was 49% (IQR, 38%-61%) predicted. Median follow-up was 19 (IQR, 14-25) months. Overall survival at 1 year was 79% (95%, CI 62%-89%; P < .001 vs the unacceptable rate), and median overall survival was 25 months (95% CI, 14 months to not reached). Median PFS was 19 months (95% CI, 13-28 months), and 2-year LC was 92% (95% CI, 69%-98%). Adverse event rates (highest grade per patient) were grade 1 to 2: n = 12 (31%), grade 3: n = 4 (10%), grade 4: n = 0, and grade 5: n = 3 (7.7%, all due to respiratory deterioration).

Conclusions and Relevance

In this trial, use of SABR in patients with fibrotic ILD met the prespecified acceptability thresholds for both toxicity and efficacy, supporting the use of SABR for curative-intent treatment after a careful discussion of risks and benefits.

Trial Registration

ClinicalTrials.gov Identifier: NCT03485378.

Plasma Cell-Free Tumor Methylome as a Biomarker in Solid Tumors: Biology and Applications

DNA methylation is a fundamental mechanism of epigenetic control in cells and its dysregulation is strongly implicated in cancer development. Cancers possess an extensively hypomethylated genome with focal regions of hypermethylation at CPG islands. Due to the highly conserved nature of cancer-specific methylation, its detection in cell-free DNA in plasma using liquid biopsies constitutes an area of interest in biomarker research. The advent of next-generation sequencing and newer computational technologies have allowed for the development of diagnostic and prognostic biomarkers that utilize methylation profiling to diagnose disease and stratify risk. Methylome-based predictive biomarkers can determine the response to anti-cancer therapy. An additional emerging application of these biomarkers is in minimal residual disease monitoring. Several key challenges need to be addressed before cfDNA-based methylation biomarkers become fully integrated into practice. The first relates to the biology and stability of cfDNA. The second concerns the clinical validity and generalizability of methylation-based assays, many of which are cancer type-specific. The third involves their practicability, which is a stumbling block for translating technologies from bench to clinic. Future work on developing pan-cancer assays with their respective validities confirmed using well-designed, prospective clinical trials is crucial in pushing for the greater use of these tools in oncology.

Re-examining prophylactic cranial irradiation in small cell lung cancer: a systematic review and meta-analysis

Background

Patients with small cell lung cancer (SCLC) are at high risk for brain metastases. Prophylactic cranial irradiation (PCI) is recommended in this population to reduce the incidence of brain metastases and prolong survival. We aimed to assesses the efficacy of PCI in this population in the era of routine brain imaging. To our knowledge, this is the first systematic review and meta-analysis to examine the use among patients who were radiographically confirmed not to have brain metastases after completion of first-line therapy.

Methods

In this systematic review and meta-analysis, cohort studies and controlled trials reporting on the use of PCI for patients SCLC were identified in EMBASE, MEDLINE, CENTRAL, and grey literature sources. The literature search was conducted on November 12, 2023. Summary data were extracted. Random-effects meta-analyses pooled hazard ratios (HR) for the primary outcome of overall survival between PCI and no intervention groups. This study is registered with the Open Science Framework, DOI:10.17605/OSF.IO/BC359, and PROSPERO, CRD42021249466.

Findings

Of 4318 identified records, 223 were eligible for inclusion. 109 reported on overall survival in formats amenable to meta-analysis; PCI was associated with longer survival in all patients with SCLC (HR 0.59; 95% CI, 0.55-0.63; p < 0.001; n = 56,770 patients), patients with limited stage disease (HR 0.60; 95% CI, 0.55-0.65; p < 0.001; n = 78 studies; n = 27,137 patients), and patients with extensive stage disease (HR 0.59; 95% CI, 0.51-0.70; p < 0.001; n = 28 studies; n = 26,467 patients). Between-study heterogeneity was significant when pooled amongst all studies (I2 = 73.6%; 95% CI 68.4%-77.9%). Subgroup analysis did not reveal sources of heterogeneity. In a subgroup analysis on studies that used magnetic resonance imaging to exclude presence of brain metastases at restaging among all patients, overall survival did not differ significantly between patients who did or did not receive PCI (HR 0.74; 95% CI, 0.52-1.05; p = 0.08; n = 9 studies; n = 1384 patients).

Interpretation

Our findings suggested that administration of PCI is associated with a survival benefit, but not when considering studies that radiographically confirmed absence of brain metastases, suggesting that the survival benefit conferred by PCI might be therapeutic rather than prophylactic.

Funding

No funding.

Analysis of prognostic germline polymorphisms in patients with advanced hepatocellular carcinoma

Background

The prognosis of hepatocellular carcinoma (HCC) is influenced by both tumor and patient specific factors. Current therapies of advanced HCC target angiogenesis and immune evasion, however there are no clinically useful biomarkers to guide clinicians.

Methods

Our aim in this retrospective cohort study was to validate single nucleotide polymorphisms (SNPs) prognostic of outcome in advanced HCC from the literature, and to analyze exploratory SNPs chosen from evaluation of the HCC tumor immune microenvironment. Using a database of patients with HCC treated with sorafenib, blood samples were genotyped, clinical variables were retrospectively collected, and SNPs were analyzed for association with progression-free survival (PFS) and overall survival (OS). A subsequent analysis was conducted to determine if identified SNPs were prognostic in trans arterial chemoembolization (TACE) treated patients.

Results

Literature review identified 7 SNPs in vascular endothelial growth factor (VEGF), eNOS, angiopoietin 2 (ANGPT2) and vascular endothelial growth factor receptor 2 (VEGFR2), however none were externally validated in our dataset. Of the 35 exploratory immunomodulatory SNPs, the following were associated with PFS or OS: CCL2 C-C motif ligand 2 (CCL2) (rs1024611), interleukin-10 (IL-10) (rs1800896), cytotoxic T-lymphocyte antigen-4 (CTLA-4) (rs231775) and NFKB1 (rs28362491).

Conclusions

SNPs identified by literature review to be prognostic in sorafenib treated patients with advanced HCC were not validated in our dataset. Our findings suggest potentially important prognostic implications of SNPs in VEGFR2, CCL2, IL-10, CTLA-4 and NFKB1 that deserve further study.

Survival Outcomes of Extensive Stage Small Cell Lung Cancer Patients Treated with Consolidative Thoracic Radiotherapy at a Tertiary Cancer Center

PURPOSE/OBJECTIVE(S)

Most small cell lung cancer cases present as Stage IV (M1) or extensive stage (ES-SCLC), which are defined as tumor extending outside the hemithorax without a tolerable radiation portal. The CREST trial demonstrated improved local control with a modest overall survival (OS) benefit at the 2-year secondary endpoint of 14% survival with consolidative thoracic radiotherapy (CTRT) compared to 3% without CTRT. Low toxicity rates were also observed. This study reports our institutional ES-SCLC experience for patients treated with CTRT.

MATERIALS/METHODS

A retrospective review was conducted on ES-SCLC patients treated with CTRT at our institution between 2014 and 2019. CTRT was defined as ≥30 Gy of thoracic radiotherapy. OS and tolerability of treatment were assessed in this population. Chemotherapy details were also captured. OS rate was determined using the Kaplan-Meier method and the time from start of CTRT to last date of follow-up or death. CTRT tolerability was determined using incidence and grade of esophagitis and radiation pneumonitis as per CTCAE v5.

RESULTS

We identified 100 ES-SCLC patients treated with any thoracic RT at our institute, of which 45 received thoracic RT for palliative intent or with <30 Gy. The remaining 55 patients received ≥30 Gy CTRT and were included for analysis. The median age was 65.1 years (range 46.6-86.9) and 36 (65%) were male. The median follow-up for this sample was 0.8 (range 0.03-4.2) years. Median chemotherapy cycles were 6 (range 1-6), most receiving ≥4 cycles (87%) and completing chemotherapy prior to CTRT initiation (91%) with a minority concurrently receiving chemotherapy and CTRT (9%). Platinum chemotherapy was the most common (96%) with 2 patients receiving etoposide alone (4%). The most common CTRT regimens were 30 Gy in 10 fractions (80%) followed by 40 Gy in 15 fractions (9%) and 45 Gy in 30 twice-daily fractions (7%). Most patients (67%) were treated with IMRT/VMAT technique, while the remaining (33%) patients were treated with 3DCRT. The median survival time was 1.3 years with 1- and 2-year OS of 57.2% (CI 44.0 - 74.3%) and 26.1% (CI 12.9 - 52.7%), respectively. CTRT was well tolerated with no grade 4+ toxicities. The most common toxicity was esophagitis with 21 patients (39%), of which 15 were G1 (28%) and 6 were G2 (11%). Radiation pneumonitis was present in 5 patients (9.2%) with 1 G1 (2%), 3 G2 (6%), and 1 G3 (2%) cases.

CONCLUSION

Consolidative TRT for ES-SCLC in this institutional series was at least as good as the reported CREST outcome with modest acute toxicities in this cohort. Disease burden at diagnosis, chemotherapy response, patterns of failure, and subsequent therapies will be further investigated.

Clinical Acceptability of Artificial Intelligence-Screened Interstitial Lung Disease (AI-ILD) in Lung Cancer Patients Treated with Radiotherapy

PURPOSE/OBJECTIVE(S)

Patients with interstitial lung disease (ILD) treated with thoracic radiotherapy (RT) are at greater risk of pulmonary toxicity. Automatic universal screening for ILD allows radiation oncologists (ROs) to risk stratify patients and implement necessary modifications to their respiratory monitoring or treatment. Automatic screening however may affect RO workload and so it is imperative to assess the clinical acceptability of this tool.

MATERIALS/METHODS

We have developed a machine learning algorithm to identify patients who are at high risk of having ILD based on RT planning computed tomography (CT) images. A quality improvement (QI) project was initiated to test feasibility and acceptability of the machine learning algorithm. If positive, the results of the machine learning algorithm were made available to ROs via structured electronic reporting. ROs were prompted to review the patient and consider expert radiologist consultation if thought appropriate. All electronic surveys and qualitative comments were summarized to describe clinical acceptability. Expert radiologist established gold standard ILD status of all patients on the study. A formal review of RO feedback was collected for all screen-positive, true-positive cases.

RESULTS

Two hundred forty cases were screened of which 45 were flagged as AI-ILD positive and the responsible RO notified. Of these 45 screen-positive cases, all continued on to RT except for 3 patients with tumor progression. From these 45, 24 surveys were completed, 21 had no prior suspicion of ILD. There were 7 true-positives, of which 1 had a survey response. Based on the survey responses, 88% of cases underwent review by the responsible RO. In 16 cases this automatic notification prompted case consultation with an expert radiologist. Expert review was performed from 10 minutes up to 53 hours after the email prompt to the radiologist, with median response time of 1.5 hours. In the 7 screen-positive, true-positive cases, only 2 were not previously known to the responsible RO. In the two cases where true-positive ILD status was previously unknown, one was a mild case of ILD and the other had previously received thoracic RT at this institution without ILD being identified, in both cases the ROs were grateful that this diagnosis was identified prior to treatment. RO confidence in the machine learning prediction was moderate due to the high proportion of false positives.

CONCLUSION

Based on available survey results, more than 75% of the screen-positive cases were reviewed by the responsible RO and two-thirds of these involved expert radiology input. RO feedback was generally positive and this tool was rated as a net benefit despite the high rate of false-positives and the need for clarification.

The Effect of PARP Inhibitor Radiosensitization on the mRNA Translational Regulation of T Cell Chemokines

PURPOSE/OBJECTIVE(S)

Immunotherapy has modestly improved survival for small cell lung cancer (SCLC) patients. Low response rate and rapid disease progression remain an intractable challenge. One of the factors that contribute to immunotherapy resistance is the lack of cytotoxic T cell infiltration. The expression of chemoattractant cytokines, like CCL5 and CXCL10, are essential for T cell infiltration. The control of chemokine expression is not fully understood, but both transcriptional and translational control pathways could play a major role. Previous studies have shown a correlation between DNA damage and chemokine expression and that PARP inhibitors (PARPi) are radiosensitizers for SCLC that increases DNA damage. The objectives of this study were to define this potential PARPi immunogenic radiosensitizing relationship.

MATERIALS/METHODS

We identified doses of olaparib+ radiation treatment (RT) that conferred radiosensitization in SCLC cell-lines by cell viability and/or clonogenic assays. Olaparib+RT induced CCL5 and CXCL10 mRNA expression was measured by qPCR across SCLC cell-lines. Protein level of chemokines was assessed by immunoblotting. SBC5 cells were treated with olaparib+RT and submitted for RNA sequencing analysis. Genes with adjusted p value<0.05 were considered significant. Protein level changes and target gene knock-out (KO) were confirmed by immunoblotting. Chemokine CXCL10 mRNA and protein level in wildtype (WT) and KO cells were measured by qPCR and western blot, respectively. A mRNA decay assay and dual-luciferase reporter assay was used to identify the region of CXCL10 mRNA that confers mRNA stability control. In vivo anti-tumor efficacy and tumor T cell infiltration studies were done in B6129F mice bearing KP1 tumors. And the T cell infiltration was measured by immune profiling.

RESULTS

In vitro, olaparib+RT significantly increased CXCL10 mRNA in all four SCLC subtype cell-lines in comparison to vehicle control. Consistently, the increase of CXCL10 protein levels (3-fold) was observed in SBC5 cells. By RNA-Seq, a top-ranking translational repressor was EIF4E2 (4EHP) mRNA. The downregulation of EIF4E2 protein by olaparib+RT was validated in four SCLC subtypes by western blot. EIF4E2 KO in HEK293 and SBC5 cells increased CXCL10 mRNA and protein level. By mRNA decay assay and western blot, the absence of EIF4E2 stabilized CXCL10 mRNA and increased CXCL10 protein levels. The dual-luciferase assay demonstrated EIF4E2 destabilizes CXCL10 mRNA via the 3'UTR of CXCL10. In vivo, immune profiling showed olaparib+RT significantly increased the total T cell and CD8+ T cell infiltration. Finally, anti-PD-L1 inhibition potentiated olaparib + IR to improve tumor control in KP1 allograft.

CONCLUSION

Our study demonstrated olaparib + RT increases CXCL10 protein levels through downregulating EIF4E2 to subsequently increase T cell infiltration. Olaparib + RT enhanced anti-PD-L1 immunotherapy efficacy and has therapeutic potential as an immunogenic radiosensitizer.

Stereotactic Ablative Radiotherapy for Oligo-Progressive Cancers: Results of the Randomized Phase II STOP Trial

PURPOSE/OBJECTIVE(S)

In the metastatic setting, there is uncertain benefit to localized eradication of one or more lesions that are progressing despite systemic therapy. This randomized phase II trial examined if patients with ≤5 sites of oligoprogression benefited from the addition of stereotactic ablative radiotherapy (SABR) to standard of care (SOC) systemic therapy.

MATERIALS/METHODS

Eligibility criteria included age ≥18 years, ECOG performance status 0-2, and oligoprogressive disease, defined as 1-5 lesions actively progressing while on systemic therapy. Patients were required to have at least 3 months of disease stability/response on systemic therapy prior to oligoprogression. After stratifying by type of systemic therapy (cytotoxic vs. non-cytotoxic), patients were randomized 2:1 to SABR to all progressing lesions plus SOC (SABR arm) vs. SOC alone (SOC arm). The trial began exclusive to non-small cell lung cancer but did not meet accrual goals and was expanded in 2019 to include all non-hematologic malignancies. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), lesional control, quality of life (QOL), toxicity, and duration of current systemic agent post-SABR.

RESULTS

Between February 2017 and June 2021, 90 patients with 125 oligoprogressive metastases were enrolled across 8 Canadian institutions, with 59 patients randomized to SABR and 31 to SOC. Median age was 67 years (IQR: 61-73 years) and 39 (43%) were female. The most common primary sites were lung (44% of patients), genitourinary (23%) and breast (13%), with the most common oligo-progressive locations being lung (43%), bone (19%), lymph nodes (14%), and liver (13%). In the SABR arm, the most common fractionations were 35 Gy/5 (38% of lesions) and 50 Gy/5 (18%). Protocol adherence in the SOC arm was suboptimal: 3 patients (10%) withdrew immediately after randomization, and 7 additional patients (23%) received high-dose or ablative therapies. Median follow-up was 31 months. There was no difference in PFS between arms (median PFS 8.4 months in the SABR arm vs. 4.3 months in the SOC arm; however, the curves cross and 2-year PFS was 9% vs. 24% respectively, p = 0.91). Median OS was 31.2 months vs. 27.4 months, respectively (p = 0.22). Lesional control with SABR was 71% vs. 39% with SOC (p = 0.002). Median duration of post-randomization first-line systemic therapy was 10.3 months vs. 7.6 months, respectively (p = 0.71). Treatment was well-tolerated with 2 (3.4%) grade 3 treatment-related toxicities in the SABR arm and no grade 4/5 related events in either arm. QOL did not differ between arms.

CONCLUSION

Despite being a well-tolerated treatment providing superior lesional control, SABR for oligoprogression did not improve PFS or OS. Results may have been impacted by withdrawals and desire for ablative treatments on the SOC arm, and this lack of equipoise may make accrual to phase III trials difficult, although larger studies in select sub-populations are desired. (NCT02756793).

Assessment of Precision Irradiation in Early Non-Small Cell Lung Cancer and Interstitial Lung Disease (ASPIRE-ILD): Primary Analysis of a Phase II Trial

PURPOSE/OBJECTIVE(S)

The use of stereotactic ablative radiotherapy (SABR) in patients with fibrotic interstitial lung disease (ILD) has been associated with an increased risk of toxicity, but patients with ILD and lung cancer may have no other options for curative-intent treatment. The goal of the ASPIRE-ILD trial was to assess the benefits and toxicities of SABR in patients with fibrotic ILD.

MATERIALS/METHODS

We enrolled patients with fibrotic ILD and a diagnosis of T1-2N0 NSCLC who were not candidates for surgery. All patients were centrally reviewed prior to enrollment to confirm the presence and subtype of ILD. After stratification by the ILD-GAP score (a measure of ILD severity and prognosis), patients were treated with SABR to a dose of 50 Gy in 5 fractions EOD (BED = 100 Gy10), with a built-in de-escalation protocol in case of unacceptable toxicity. The primary endpoint was overall survival (OS), powered to distinguish 1-year OS >70% vs. an unacceptable rate of ≤50%. Secondary endpoints included toxicity (CTC-AE version 4.0), progression-free survival (PFS), local control (LC), patient-reported outcomes (FACT-L quality of life and cough severity), and changes in pulmonary function tests (PFTs). The study pre-specified that SABR would be considered worthwhile if median OS was >1 year, with a grade 3-4 toxicity risk <35% and a grade 5 toxicity risk <15%. Target accrual was 39 treated patients.

RESULTS

Thirty-nine patients were enrolled and treated with SABR between March 2019 and January 2022, all to a dose of 50 Gy in 5 fractions, at 5 institutions in Canada and 1 in Scotland. Median age was 78 years (interquartile range: 67-83), 59% were male, and 92% had a history of smoking (median 43 pack-years). At baseline, 70% reported dyspnea, median FEV1 was 80% predicted and median DLCO was 49% predicted. ILD-GAP scores were as follows: ≤2 (i.e., best ILD status): n = 14; 3-5: n = 23; ≥6 (i.e., worst ILD status): n = 2. Median follow-up was 19 months. OS at 1-year was 78.9% (p<0.001 by binomial test vs. the unacceptable rate). Median OS was 25 months, median PFS was 19 months, and 2-year LC was 92%. AE rates (possibly, probably or definitely related) were as follows (highest grade per patient): grade 1-2: n = 12 (31%); grade 3: n = 4 (10%); grade 4; n = 0; grade 5 n = 3 (7.7%, all due to respiratory deterioration). AE rates did not differ by ILD-GAP category or ILD subtype. FACT-L scores trended downward over time (p = 0.07), and cough severity scale scores worsened over time (p = 0.02). Comparing last-available PFTs with baseline, DLCO declined (median: -4%; p = 0.046), FVC trended downward (median: -2.5%; p = 0.11), and FEV1 remained stable (median change: 0%).

CONCLUSION

The use of SABR in patients with ILD met the pre-specified acceptability thresholds for both toxicity and efficacy, supporting the use of SABR for curative-intent treatment after a careful discussion of risks and benefits. Further studies exploring pharmacologic options to reduce toxicity may be beneficial in this population. ().

Association of Artificial Intelligence-Screened Interstitial Lung Disease with Radiation Pneumonitis and Mortality in Locally Advanced Non-Small Cell Lung Cancer

PURPOSE/OBJECTIVE(S)

Radiation pneumonitis (RP) is a common and dose-limiting toxicity following radiotherapy for non-small cell lung cancer (NSCLC). Patients with interstitial lung disease (ILD) are believed to be at increased risk of developing complications including RP, ILD progression, or death. An automated method to identify patients prior to radiotherapy at high risk of developing toxicities or death may allow clinicians to mitigate risk through informed treatment planning and careful patient monitoring.

MATERIALS/METHODS

All locally advanced NSCLC patients treated with definitive radiation from 2006-2021 with a minimum 1 year of follow-up were assessed. RP and mortality data were prospectively collected and retrospectively reviewed. A convolutional neural network (CNN) was previously developed and validated to identify patients with radiographic ILD using planning computed tomography (CT) images, with an accuracy of 0.82. Planning CT scans for the retrospective cohort were used as input to the CNN, with artificial intelligence-screened ILD (AI-ILD) score as an output. AI-ILD scores above our established threshold were labeled as AI-ILD+. The association between AI-ILD score, AI-ILD+/-, mean lung dose (MLD), and the primary outcome of grade ≥2 (G2+) RP or mortality, as well as the secondary outcomes of G2+ RP and mortality were assessed using Wilcoxon rank sum test, univariate and multivariable logistic regression, and Kaplan-Meier survival analysis.

RESULTS

Of 799 patients reviewed, 745 eligible patients were included in the analysis; grade 0-5 RP was reported in 51.3%, 27.1%, 16.9%, 4.0%, 0.1%, and 0.5% of patients respectively. Overall, 22.9% of patients were AI-ILD+, and therefore at high risk (>20% chance) of having true ILD. On UVA, AI-ILD score, AI-ILD+ and MLD were significantly associated with the primary outcome of G2+ RP or mortality, as well as the secondary outcome of mortality. However, only MLD was significantly associated with the secondary outcome of G2+ RP. On MVA, both AI-ILD+ (OR 1.42, 95% CI 1.02-1.97, p = 0.04) and MLD (OR 1.13, 95% 1.05-1.21, p = 0.008) were significantly associated with G2+ RP or mortality. On Kaplan-Meier analysis, the median toxicity-free survival (TFS) time for AI-ILD+ and AI-ILD- patients were 1.7 and 3.4 years respectively, with a 2-year TFS of 48.3% vs. 59.3% (log-rank test: p = 0.02). There was no significant difference in rates of G2+ RP.

CONCLUSION

The AI-ILD algorithm can detect high risk patients with significantly decreased TFS following definitive treatment for NSCLC. AI-ILD classification was not associated with a significant difference in rates of RP when accounting for MLD. Future work will focus on improving the classification algorithm, expert radiologist validation of this dataset, and exploring reasons for the mortality difference in AI-ILD+ patients.

Novel therapeutic combinations with PARP inhibitors for small cell lung cancer: A bench-to-bedside review

Small cell lung cancer (SCLC) is treated as a monolithic disease despite the evident intra- and intertumoral heterogeneity. Non-specific DNA-damaging agents have remained the first-line treatment for decades. Recently, emerging transcriptomic and genomic profiling of SCLC tumors identified distinct SCLC subtypes and vulnerabilities towards targeted therapeutics, including inhibitors of the nuclear enzyme poly (ADP-ribose) polymerase (PARPi). SCLC cell lines and tumors exhibited an elevated level of PARP1 protein and mRNA compared to healthy lung tissues and other subtypes of lung tumors. Notable responses to PARPi were also observed in preclinical SCLC models. Clinically, PARPi monotherapy exerted variable benefits for SCLC patients. To date, research is being vigorously conducted to examine predictive biomarkers of PARPi response and various PARPi combination strategies to maximize the clinical utility of PARPi. This narrative review summarizes existing preclinical evidence supporting PARPi monotherapy, combination therapy, and respective translation to the clinic. Specifically, we covered the combination of PARPi with DNA-damaging chemotherapy (cisplatin, etoposide, temozolomide), thoracic radiotherapy, immunotherapy (immune checkpoint inhibitors), and many other novel therapeutic agents that target DNA damage response, tumor microenvironment, epigenetic modulation, angiogenesis, the ubiquitin-proteasome system, or autophagy. Putative biomarkers, such as SLFN11 expression, MGMT methylation, E2F1 expression, and platinum sensitivity, which may be predictive of response to distinct therapeutic combinations, were also discussed. The future of SCLC treatment is undergoing rapid change with a focus on tailored and personalized treatment strategies. Further development of cancer therapy with PARPi will immensely benefit at least a subset of biomarker-defined SCLC patients.

Abstract 3396: Identification of small cell lung cancer stage-specific DNA methylation in patients using liquid biopsies

Introduction: Small cell lung cancer (SCLC) is a deadly disease and patients often suffer from recurrent disease. Biologic mechanisms of recurrence are unclear. Epigenetic mechanisms, like DNA methylation, may be operant. SCLC is rarely resected; therefore, the SCLC methylome is understudied due to scarce tumor tissue.

Methods: In this study, we examined the pre-treatment methylome of 72 SCLC patients at our institution through cell-free methylated DNA immunoprecipitation sequencing (cfMeDIP-seq) on plasma cell-free DNA (cfDNA) and on sheared genomic DNA from paired peripheral blood leukocytes (PBLs) (n = 72) to increase tumor signal specificity. cfMeDIP-seq was also performed on an independent cohort of healthy non-cancer controls (n = 20) and on tumors from circulating tumor cell-derived xenograft (CDX) models (n = 12 CDXs of 72 patients). cfMeDIP-seq libraries were sequenced at a depth of 100 million reads, paired-end, on the NovaSeq 6000. For all bioinformatic analyses, chromosomes 1-22 were binned into 300-bp windows (n = 9.6e6 genome-wide windows); reads from cfMeDIP-seq were tallied per bin. To filter out noise from non-tumor cells, ENCODE blacklist regions (n = 1e6 windows) were removed and CG-rich (&gt;5 CGs per window), PBL-associated windows with MeDEStrand-converted beta-values &lt; 0.2 were kept (n = 190,769 windows). Subsequent cfDNA analyses were performed using these 190,769 windows.

Results: 33 (45.8%) and 39 (54.2%) of the 72 patients had limited-stage (LS) and extensive-stage (ES) SCLC, respectively. Most were current or former smokers (65/72, 90.3%). Using filtered windows (n = 190,769), methylated cfDNA from SCLC were distinguished from healthy controls: SCLC cfDNA was enriched for hypermethylated CpG islands and shore regions, whereas controls had more methylated open-sea regions. SCLC cohort by consensus clustering of the top 5000 most variant windows revealed two distinct cfDNA methylation patterns. Cluster A (9 ES, 22 LS) and Cluster B (33 ES, 11 LS) were significantly different by stage (X2(1) = 13.79, p &lt; 0.001). There was no significant difference in sex (p = 0.81). Patients in Cluster A had a lower concentration of cfDNA (median = 7.2ng/ml) compared to Cluster B (median = 15.9ng/ml) but not statistically significant (p = 0.33). High concordance between genome-wide methylome profiles was found between paired patient cfDNA and CDX tumor, demonstrating that cfDNA is representative of tumor methylation (Pearson's correlation median r = 0.86).

Conclusion: We identified stage-specific methylation patterns in the plasma of SCLC patients using the cfMeDIP-seq assay that may reveal novel epigenetic and biologic mechanisms of SCLC disease progression. Moreover, CDXs recapitulate the methylome of SCLC cell-free patient samples highlighting their utility in future work as representative models for methylome analysis.

Citation Format: Sami Ul Haq, Sabine Schmid, Mansi K. Aparnathi, Katrina Hueniken, Luna J. Zhan, Danielle Sacdalan, Janice J.N. Li, Devalben Patel, Dangxiao Cheng, Vivek Philip, Geoffrey Liu, Scott V. Bratman, Benjamin H. Lok. Identification of small cell lung cancer stage-specific DNA methylation in patients using liquid biopsies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3396.

Stereotactic radiosurgery (SRS) versus whole brain radiation therapy (WBRT) in patients with small cell lung cancer (SCLC) and intracranial metastatic disease (IMD): A systematic review and meta-analysis

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Background: Patients with SCLC are at high risk for the development of IMD and, subsequently, rapid intracranial progression. SRS has supplanted WBRT as first-line treatment for IMD in most solid cancers, but WBRT remains first-line treatment for IMD in SCLC patients. Data on SRS in SCLC are limited to small retrospective studies. Methods: Studies reporting on SRS in SCLC patients with IMD were collected from EMBASE, MEDLINE, CENTRAL, and grey literature sources (n = 3,732 studies). Random-effects meta-analysis pooled hazard ratios (HR) for overall survival (OS) between SRS and WBRT ± SRS boost, as well as medians for OS in months (mo) and risk rates for intracranial local (LC) and intracranial distant control (DC) in single-arm SRS studies. Results: OS following SRS was non-inferior compared with WBRT ± SRS boost (HR 0.90; 95% confidence interval (95CI), 0.73-1.10; n = 7 studies; n = 18,130 patients), and superior compared with WBRT alone (HR 0.80; 95CI, 0.66-0.96; n = 7 studies; n = 16,961 patients). Pooled median OS from single-arm studies following SRS was 8.99 mo (95CI, 7.86-10.15; n = 14 studies; n = 1,682 patients). Pooled LC and DC estimates following SRS were 81% (95CI, 67%-99%) and 66% (95CI, 50%- 86%), respectively, at 6 mo, and 78% (95CI, 61%-98%) and 58% (95CI, 46%-75%), respectively, at 12 mo. Conclusions: This systematic review and meta-analysis provides evidence that SRS may achieve analogous survival outcomes compared with WBRT in patients with SCLC and IMD, indicating that a subset of SCLC patients may benefit from first-line SRS treatment. Prospective trials should investigate the impact of metastatic burden as well as LC and DC differences between WBRT- and SRS-treated SCLC patients.

Targeting the Ubiquitin-Proteasome System Using the UBA1 Inhibitor TAK-243 is a Potential Therapeutic Strategy for Small-Cell Lung Cancer

PURPOSE

Small cell lung cancer (SCLC) is an aggressive disease with an overall 5-year survival rate of less than 10%. Treatment for SCLC with cisplatin/etoposide chemotherapy (C/E) ± radiotherapy has changed modestly over several decades. The ubiquitin-proteasome system is an underexplored therapeutic target for SCLC. We preclinically evaluated TAK-243, a first-in-class small molecule E1 inhibitor against UBA1.

EXPERIMENTAL DESIGN

We assessed TAK-243 in 26 SCLC cell-lines as monotherapy and combined with C/E, the PARP-inhibitor, olaparib, and with radiation using cell viability assays. We interrogated TAK-243 response with gene expression to identify candidate biomarkers. We evaluated TAK-243 alone and in combination with olaparib or radiotherapy with SCLC patient-derived xenografts (PDX).

RESULTS

Most SCLC cell lines were sensitive to TAK-243 monotherapy (EC50 median 15.8 nmol/L; range 10.2 nmol/L-367.3 nmol/L). TAK-243 sensitivity was associated with gene-sets involving the cell cycle, DNA and chromatin organization, and DNA damage repair, while resistance associated with cellular respiration, translation, and neurodevelopment. These associations were also observed in SCLC PDXs. TAK-243 synergized with C/E and olaparib in vitro across sensitive and resistant SCLC cell lines. Considerable TAK-243-olaparib synergy was observed in an SCLC PDX resistant to both drugs individually. TAK-243 radiosensitization was also observed in an SCLC PDX.

CONCLUSIONS

TAK-243 displays efficacy in SCLC preclinical models. Enrichment of gene sets is associated with TAK-243 sensitivity and resistance. TAK-243 exhibits synergy when combined with genotoxic therapies in cell lines and PDXs. TAK-243 is a potential therapeutic strategy to improve SCLC patient outcomes, both as a single agent and in combination with existing therapies.

Longitudinal Assessment of Health Utility Scores, Symptoms and Toxicities in Patients with Small Cell Lung Cancer Using Real World Data

INTRODUCTION

Recent advances in small cell lung cancer (SCLC) treatments necessitate a better understanding of real-world health utility scores (HUS) in patients treated under current standards to facilitate robust pharmaco-economic assessments.

METHODS

In this single institution cohort observational study, HUS were evaluated in patients with SCLC through EQ-5D questionnaires at outpatient visits (encounters). In addition, patients completed questionnaires relating to treatment toxicities and cancer symptoms. Clinical and pathological variables were abstracted from electronic medical records and disease status at each patient visit was documented. The impact of these variables on HUS were explored.

RESULTS

There were 282 clinical encounters (12% newly diagnosed; 37% stable on treatment; 22% progressing on treatment; 29% stable off therapy/other) in 111 SCLC patients (58% male; 64% extensive stage (ES) SCLC). At the first encounter 29% of patients had an ECOG performance status (PS) ≥ 2. ES-SCLC, bone metastases, female sex, progressive disease and/or PS were each significantly associated with decreased HUS in multivariable analyses. Patients clinically stable on first line therapy had generally steady HUS longitudinally, with differences in HUS between limited disease (LD) and ES patients emerging as treatment progressed. Decreased HUS were associated with increased severity of the majority of measured symptoms (fatigue/tiredness, loss of appetite, pain, drowsiness, shortness of breath, anxiety, depression, and overall well-being; each p<0.001), supporting the value of EQ-5D-derived HUS in assessing health utility.

CONCLUSION

Our HUS values in chemotherapy-treated SCLC are clinically relevant and are associated with specific clinico-demographic, symptom and toxicity factors.

Binary pan-cancer classes with distinct vulnerabilities defined by pro- or anti-cancer YAP/TEAD activity

Cancer heterogeneity impacts therapeutic response, driving efforts to discover over-arching rules that supersede variability. Here, we define pan-cancer binary classes based on distinct expression of YAP and YAP-responsive adhesion regulators. Combining informatics with in vivo and in vitro gain- and loss-of-function studies across multiple murine and human tumor types, we show that opposite pro- or anti-cancer YAP activity functionally defines binary YAP^on or YAP^off cancer classes that express or silence YAP, respectively. YAP^off solid cancers are neural/neuroendocrine and frequently RB1^-/-, such as retinoblastoma, small cell lung cancer, and neuroendocrine prostate cancer. YAP silencing is intrinsic to the cell of origin, or acquired with lineage switching and drug resistance. The binary cancer groups exhibit distinct YAP-dependent adhesive behavior and pharmaceutical vulnerabilities, underscoring clinical relevance. Mechanistically, distinct YAP/TEAD enhancers in YAP^off or YAP^on cancers deploy anti-cancer integrin or pro-cancer proliferative programs, respectively. YAP is thus pivotal across cancer, but in opposite ways, with therapeutic implications.

Limited-stage small cell lung cancer: Outcomes associated with prophylactic cranial irradiation over a 20-year period at the Princess Margaret Cancer Centre

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Prophylactic cranial irradiation (PCI) was more commonly used in younger patients.

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PCI utilization rates did not change throughout our 20-year institutional experience.

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PCI was associated with improved OS and lower brain metastasis risk, independent of MRI follow-up or era of treatment.

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For LS-SCLC patients with good thoracic response, PCI remains the standard-of-care.

Background & purpose

Prophylactic cranial irradiation (PCI) is recommended for limited-stage small-cell lung cancer (LS-SCLC) patients with good response to concurrent chemoradiation. We report our institution’s 20-year experience with this patient population and associated clinical outcomes.

Materials & methods

A retrospective cohort of consecutive LS-SCLC patients treated with curative intent chemoradiation at our institution (1997–2018) was reviewed. Overall survival (OS) was calculated using the Kaplan-Meier method, and significant covariates determined by the Cox proportional hazards model. Covariates predictive of PCI were determined using Fisher's exact test and the Mann-Whitney test. Brain failure risk (BFR) was calculated using the cumulative incidence method treating death as a competing event. Treatment cohorts (historic vs. contemporary) were stratified by the median year of diagnosis (2005).

Results

A total of 369 patients with LS-SCLC were identified, of which 278 patients were notionally PCI eligible. PCI was given to 196 patients (71%). Younger age was associated with PCI utilization (p < 0.001). PCI utilization rates did not change between the historic and contemporary treatment era (p = 0.11), whereas magnetic resonance imaging (MRI) use at baseline and follow-up became more prevalent in the contemporary era (p = <0.001). On multivariable analysis, PCI utilization was associated with improved OS (HR 1.88, 95% CI 1.32–2.69) and decreased BFR (HR 4.66, 95% CI 2.58–8.40). Patients who had MRI follow-up had a higher incidence of BFR (HR 0.35, 95% CI 0.18–0.66) in multivariable analyses.

Conclusions

For LS-SCLC patients at our institution, PCI is more frequently utilized in younger patients, and the utilization rate did not change significantly over the past 20 years. PCI was independently associated with improved OS and lower BFR. Omission of PCI in LS-SCLC patients should not be routinely practiced in the absence of further prospective data.

Implementation of Cardiac Stereotactic Radiotherapy: From Literature to the Linac

Stereotactic radiotherapy (SBRT) has been applied to treat cardiac arrhythmias, but our institution had not yet implemented this technique. Here, we explain how we used implementation science and knowledge translation to provide cardiac SBRT to a critically ill patient with malignancy-associated refractory ventricular tachycardia. We reviewed the critical factors that enabled the implementation of this urgent treatment, such as the context of the implementation, the characteristics of the intervention, and the stakeholders. These principles can be used by other radiation programs to implement novel treatments in urgent settings, where the gold standard process of planning and developing policies and protocols is not possible.

PARP inhibitors for small cell lung cancer and their potential for integration into current treatment approaches

Small cell lung cancer (SCLC) is a very aggressive, highly lethal, neuroendocrine tumor that constitutes 15% of all lung cancer cases. It is characterized by its rapid disease progression and high relapse rate leading to poor survival for diagnosed patients. Recently, poly (ADP-ribose) polymerase inhibitors (PARPi) have emerged as a novel therapeutic strategy for SCLC. Preclinical studies have demonstrated that PARPi possesses cytotoxic activity as a single-agent and in combination with other anti-cancer agents. Predictive biomarkers of response to PARPi, such as SLFN11, have also been described in SCLC. This review aims to summarize the recent preclinical investigations and the relevant clinical trials that evaluate PARPi in SCLC. Here, we highlight the potential role of PARPi in a biomarker-selected manner and in combination with chemotherapy, targeted agents, radiotherapy and immunotherapy.

Predictors of and longitudinal assessment of health utility scores in patients with small cell lung cancer using real-world data

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Background: Recent advances in small cell lung cancer (SCLC) treatments necessitate a better understanding of health utility scores (HUS) of patients treated under standard regimens to facilitate robust pharmaco-economic assessments. HUS collected in clinical trials may be inherently skewed due to restrictive eligibility criteria, highlighting the need for real-world data. Methods: In this cohort observational study, HUS were evaluated in SCLC patients through EQ-5D surveys. We also evaluated patient reported (pr) ECOG performance status (PS)), treatment toxicities (modified patient reported (mpr) CTCAE) and symptoms (Edmonton Symptom Assessment System, ESAS). Clinical data were abstracted from electronic medical records. The impact of these variables on HUS was explored using regression. Results: Of 282 clinical encounters (12% newly diagnosed; 37% stable on treatment; 22% progressing; 29% stable off therapy/other) in 111 SCLC patients (58% male; 64% extensive stage), 29% had pr-ECOG PS ≥ 2 at the first encounter. Mean HUS in treatment naïve patients with limited disease was 0.848 (SEM = 0.028); for extensive stage, mean HUS = 0.715 (SEM = 0.046). Extensive stage (β = -0.12; p = 0.03), bone metastases (β = -0.10; p = 0.04), females (β = -0.07; p = 0.006), and pr-ECOG PS ≥ 2 (β = -0.21; p < 0.001) were each associated with decreased HUS in multivariable analyses. When excluding pr-ECOG PS from the model (highly correlated with HUS), progressive disease (β = -0.07; p = 0.02) was also associated with decreased HUS. Longitudinally, in patients with disease stability, HUS were unchanged in limited disease, but slowly decreased for extensive stage over time. HUS were inversely associated with increasing severity of most measured toxicities (mpr-CTCAE rho values ranged from -0.34 to -0.47) and symptoms (rho values -0.27 to -0.54). Conclusions: HUS in SCLC is impacted by the presence of extensive stage and bone metastases, in addition to cancer symptoms and treatment toxicities. The values reported from this real-world sample provides a basis in which to compare with new SCLC therapies in health technology assessments. [Table: see text]

The Utility of Liquid Biopsies in Radiation Oncology

The use of therapeutic radiation is primarily guided by clinicopathologic factors and medical imaging, whereas molecular biomarkers currently play a comparatively minor role in most settings. Liquid biopsies provide a rich source of noninvasive tumor-specific biomarkers and are amenable to repeated and noninvasive assessment. Here, we review the current status of liquid biopsies and their potential impact on the field of radiation oncology. We focus on established and emerging approaches to analyze circulating tumor DNA and circulating tumor cells from peripheral blood. These promising classes of biomarkers could have an outsized impact on cancer management by meaningfully stratifying patients into risk groups, tracking radiation therapy efficacy during and after treatment, and identifying patients with radiosensitive or radioresistant disease. Finally, we highlight opportunities for future investigation including the need for prospective interventional studies employing liquid biopsies to guide the management of radiation therapy-treated patients.

Outcomes of multimodal therapy in a large series of patients with anaplastic thyroid cancer

BACKGROUND

The role of radiotherapy (RT) in the treatment of patients with anaplastic thyroid cancer (ATC) for local tumor control is critical because mortality often is secondary to complications of tumor volume rather than metastatic disease. Herein, the authors report the long-term outcomes of RT for patients with ATC.

METHODS

A total of 104 patients with histologically confirmed ATC were identified who presented to the study institution between 1984 and 2017 and who received curative-intent or postoperative RT. Locoregional progression-free survival (LPFS), overall survival (OS), and distant metastasis-free survival were assessed.

RESULTS

The median age of the patients was 63.5 years. The median follow-up was 5.9 months (interquartile range, 2.7-17.0 months) for the entire cohort and 10.6 months (interquartile range, 5.3-40.0 months) for surviving patients. Thirty-one patients (29.8%) had metastatic disease prior to the initiation of RT. Concurrent chemoradiation was administered in 99 patients (95.2%) and 53 patients (51.0%) received trimodal therapy. Systemic therapy included doxorubicin (73.7%), paclitaxel with or without pazopanib (24.3%), and other systemic agents (2.0%). The 1-year OS and LPFS rates were 34.4% and 74.4%, respectively. On multivariate analysis, RT ≥60 Gy was associated with improved LPFS (hazard ratio [HR], 0.135; P = .001) and improved OS (HR, 0.487; P = .004), and trimodal therapy was associated with improved LPFS (HR, 0.060; P = .017). The most commonly observed acute grade 3 adverse events included dermatitis (20%) and mucositis (13%), with no grade 4 subacute or late adverse events noted (adverse events were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events [version 4.0]).

CONCLUSIONS

RT appears to demonstrate a dose-dependent, persistent LPFS and OS benefit in patients with locally advanced ATC with an acceptable toxicity profile. Aggressive RT should be strongly considered for the treatment of patients with ATC as part of a trimodal treatment approach.

Abstract 3925: A screen for epigenetic radiosensitizers in small cell lung cancer

Objective: Small cell lung cancer (SCLC) is a highly aggressive neuroendocrine malignancy. Post-platinum-based chemotherapy, rapid relapse of chemoresistant tumor is commonly seen. Unidentifiable causative mutations and from reversible nature of acquired chemoresistance, involvement of epigenetic switch regulating SCLC progression is evident. Aim of this screen is to identify epigenetic modifiers that could sensitize SCLC cells to ionizing radiation (IR).

Methods: To recapitulate molecular diversity of patients, a range of SCLC cell lines (n=10) from classic or variant and ASCL1 or NeuroD1 sub-groups, driven by varying MYC family amplifications were picked. Short term viability experiment was setup in 3 groups: (a) Epigenetic monotherapy: cells were screened with 10 epigenetic modifiers (0 to 10 µM). (b) IR monotherapy: cells were irradiated from 0 to 8 gy. (c) Combination therapy: cells were treated with different doses of epigenetic probes and IR. Radiosensitization was measured as dose modifying factor at SF63 for each epigenetic modulator.

Results: (a) Epigenetic monotherapy: All 10 cell lines were responsive to GSK-J4 (KDMi, IC50 3.1-0.9 µM), SAHA (HDACi, IC50 2.9-0.79 µM) and JIB04 (Jumonji KDMi, IC50 74-2.4 nM). Other interesting epi-probe to which 9/10 cell lines responded was JQ1 (BET-BRDi, IC50 5.7 to 0.15 µM, except SBC-5). Compounds with lesser universal potency were MS023 (PRMTi), UNC0642 (G9a/GLPi) and UNC1999 (EZH2i). All cell lines were irresponsive to PFI3 (SMARCA2/4 BRDi), BAY598 (SMYD2 MTi) and OICR-9429 (WDR5i). (b) IR monotherapy: All 10 cell lines demonstrated different sensitivities to 4 days of IR. They’re ranked in descending order of radiosensitivity as H446, H82, SHP77, LX22, H889, H1092, H196, H69, SBC5, H526. (c) Epi-probes + IR combination therapy: Epi-probes ranked in descending order of number of cell lines they radiosensitized are JQ1, JIB-04, GSK-J4, SAHA, UNC0642, BAY598, MS023, UNC1999, OICR9429 and PFI3. Interestingly, drugs that demonstrated potency as a single agent did not necessarily radiosensitize the cell lines. On the contrary, certain epi-probes that were ineffective as monotherapy radiosensitized a few of the cell lines. H82 is a sensitive cell line which was radiosensitized by all epi-probes used.

Conclusions: This screen shows that treating cells with IR in conjunction with epigenetic modifiers may potentially improve therapeutic efficacy of radiotherapy in SCLC. Further validation is being done with long term colonogenic assays followed by in vivo studies for the potent radiosensitizing candidate drugs. It would be therapeutically relevant to correlate the probability of radiosensitization by an epi-probe with the molecular profile of the patients for more predictive targeted therapeutics.

Citation Format: Mansi K. Aparnathi, Lifang Song, Ratheesh Subramaniam, Richard Marcellus, Rima Al-awar, Benjamin H. Lok. A screen for epigenetic radiosensitizers in small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3925.

Abstract 2699: Targeting an ubiquitin-activating enzyme in small-cell lung cancer (SCLC)

Background: Despite valiant efforts to improve patient outcomes, small cell lung cancer (SCLC) (~15-17% of lung cancer) remains an aggressive lung cancer, with an overall five-year survival of 7%. Current first-line therapy (chemotherapy+/-radiation) has not changed in 30+ years. TAK-243, an inhibitor of the ubiquitin activating enzyme (UAE), E1 (encoded by UBA1), poses a novel approach for cancer therapy.

TAK-243 limits the formation of ubiquitin conjugates that ultimately mediate many cellular processes, including DNA repair signalling and protein degradation. Consequently, TAK-243 may disrupt cancer-specific dependencies of UAE to induce malignant cell death, and potentiate radiation-induced DNA damage. The discovery publication revealed that TAK-243 is especially potent in 2 SCLC cell-lines compared to healthy breast and fibroblastic tissues. With these limited data, the potential benefit of this novel agent as monotherapy and in combination with chemotherapy for SCLC has yet to be elucidated.

Methods: We assessed the anti-proliferative effect of TAK-243 monotherapy in a large panel (n = 10) of variant and classical SCLC cell-lines, including assorted MYC family member amplifications and different UBA1 mRNA expression levels. TAK-243 EC50 single agent doses were determined by treating cell-lines with incremental concentrations of TAK-243 (0-1μM). For combinatorial analysis, TAK-243 (0-1μM) was administered to cell-lines alongside cisplatin/etoposide (CE) at cell-line specific optimized doses yielding 30-35% kill by CE. Short-term efficacy was determined by a cell viability resazurin assay, 48 hours after treatment initiation. ΔEC50 was measured as the single agent EC50 subtracted by the EC50 of TAK-243+CE. Positive ΔEC50 values show potential synergy between TAK-243 and CE.

Results:

Single-agent therapy. SCLC cell-lines demonstrated a range of sensitives to TAK-243 monotherapy after 48 hours. The cell-lines tested are ranked from highest to lowest sensitivity: NCI-H82, NCI-H69, NCI-H1618, LX22 (ex-vivo cultured PDX), NCI-H1092, NCI-H446, SHP77 and NCI-H196; with EC50 values ranging from 18nM to 80nM. However, NCI-H526, NCI-H889, and SBC-5 were non-responsive to therapy at 1μM.

Combination therapy. TAK-243 upon combination treatment with CE revealed ΔEC50 values ranging from 5.23-14.54nM. NCI-H82, NCI-H69, SHP77 and NCI-H1092 demonstrated potential chemosensitivity to combination treatment.

Conclusions: These data begin to hint at synergy between TAK-243 and CE, where lower doses of TAK-243 may be required for certain SCLC cell-lines when used in combination. These preliminary results suggest that TAK-243 may have the potential to improve the current SCLC standard therapies in molecular defined subgroups. These results are being confirmed in additional cell-lines and through in vivo experiments using patient-derived xenograft models of SCLC.

*S.M and M.K.A contributed equally to this work

Citation Format: Safa Majeed, Mansi K. Aparnathi, Lifang Song, Aaron D. Schimmer, Ming S. Tsao, Geoffrey Liu, Benjamin H. Lok. Targeting an ubiquitin-activating enzyme in small-cell lung cancer (SCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2699.

Positron-Emission Tomographic Imaging of a Fluorine 18-Radiolabeled Poly(ADP-Ribose) Polymerase 1 Inhibitor Monitors the Therapeutic Efficacy of Talazoparib in SCLC Patient-Derived Xenografts

INTRODUCTION

Inhibitors of poly-(ADP)-ribose polymerase (PARP) are promising therapeutics for SCLC. We tested whether PARP inhibitor (PARPi) target engagement as measured by a fluorine 18-radiolabeled PARPi ([¹⁸F]PARPi) has the potential to predict drug efficacy in vivo.

METHODS

Tumor growth inhibition during daily talazoparib treatment was evaluated in mice engrafted with SCLC patient-derived xenografts to evaluate talazoparib efficacy at multiple doses. Mice were intravenously injected with [¹⁸F]PARPi radiotracer at multiple timepoints after single doses of oral talazoparib to quantitatively assess the extent to which talazoparib could reduce tumor radiotracer uptake and positron-emission tomographic (PET)/computer tomographic activity. Tumors were harvested and tumor poly-(ADP) ribose level was measured by enzyme-linked immunosorbent assay.

RESULTS

A dose range of talazoparib with differential therapeutic efficacy was established, with significant delay in time to reach 1000 mm³ for tumors treated with 0.3 mg/kg (p = 0.02) but not 0.1 mg/kg talazoparib. On PET/computed tomography with [¹⁸F]PARPi, reduction in [¹⁸F]PARPi uptake after talazoparib dosing was consistent with talazoparib clearance, with reduction in PET activity attenuating over 24 hours. Talazoparib target engagement, measured by maximum tumor PET uptake, increased in a dose-dependent manner (3.9% versus 2.1% injected dose/g for 0.1 and 0.3 mg/kg at 3 hours post-talazoparib, p = 0.003) and correlated with PARP enzymatic activity among individual tumors as measured by total tumor poly-(ADP) ribose (p = 0.04, R = 0.62 at 1 hour post-talazoparib).

CONCLUSIONS

PET imaging using [¹⁸F]PARPi has the potential to be a powerful tool in treatment monitoring by assessing PARPi target engagement in real-time.

Quantifying EpCAM heterogeneity of circulating-tumor-cells (CTCs) from small cell lung cancer (SCLC) patients

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Background: Tumor heterogeneity and evolution of SCLC is poorly defined. Serial longitudinal interrogation of tumor heterogeneity from CTCs detected in peripheral blood patient (pt) samples is a potential strategy to address this gap in knowledge. However, existing technology is generally limited to the capture and enumeration of CTCs, without a high-throughput method to quantify phenotypic properties. Here, we evaluated a novel nanotechnology platform – nanoparticle-mediated magnetic ranking cytometry (MagRC) to profile SCLC CTCs by EpCAM protein expression. Methods: Blood samples from 20 SCLC pts were processed through the MagRC platform. Magnetic nanoparticles conjugated with anti-EpCAM antibodies were incubated with whole blood samples then introduced into the MagRC device where CTCs are sorted by differently sized nickel micromagnets within microfluidic channels. Captured CTCs are ranked into 8 zones that correlate with EpCAM expression levels (zone 1 = highest to 8 = lowest). For 8 pts, all samples were processed at a 1mL/hr flow rate (fr), and for 12 pts, a 0.5mL/hr fr was also studied; 66% of all chips were processed at a 1ml/hr fr and 34% at a 0.5ml/hr fr. The average zone for each chip was compared to the flow rate, age, and stage (extensive-stage (ES) vs limited-stage (LS)). The differences were tested using the Wald test within the linear mixed effects model. Results: Among 20 pts, 11 were ES; 9 were LS. Median age at diagnosis was 69 years old (yo); 65% were male. We detected CTCs in 12 of 20 pts (60%), similar to other studies. When comparing the MagRC-ranked EpCAM zone, the 0.5mL/hr fr demonstrated a lower median zone (4.3 vs 6.5; p < 0.001) as compared to the 1mL/hr rate. Interestingly, pts > 65 yo had a higher median zone (6.2 vs. 3.5; p = 0.019) compared to those ≤65 yo. The effect remained significant after controlling for flow rate (p = 0.002). No EpCAM zone difference was detected between ES and LS. Conclusions: We demonstrate the ability of MagRC to quantify EpCAM expression levels of CTCs from SCLC pts. We observed a higher MagRC zone (i.e. lower EpCAM expression) from pts > 65 yo. This observation requires validation in larger datasets along with continued investigation into the biology of SCLC CTCs.

Langerhans cell histiocytosis in adults is associated with a high prevalence of hematologic and solid malignancies

Background

Langerhans cell histiocytosis (LCH) is a rare disorder of histiocyte proliferation. Previous case studies suggest a higher prevalence of hematologic and solid malignancies among LCH patients, possibly due to treatment with tumorigenic agents such as etoposide. We report the first large, single‐institution experience of adult LCH patients with additional malignancies to study the characteristics of these patients.

Methods

We identified 132 consecutive patients >18 years of age with histologically confirmed LCH at our center between 1990 and 2015. Demographics and detailed oncologic history were recorded to identify patients with additional malignancies.

Results

Of 132 adult LCH patients, 42 (32%) patients had an additional malignancy. There were 53 malignancies among the 42 patients, with 31 (58%) preceding LCH diagnosis, 11 concurrent (≤3 months; 21%) with LCH diagnosis, and 11 (21%) after. Median age was 54 years (range 28‐89) with a median follow‐up of 3.7 years (0.1‐22.2) for this cohort. OS at 3 years was 98% in patients with LCH alone and 82% among patients with additional malignancies, with 30 (71%) alive at last follow‐up. Solid tumors, lymphomas, and other hematologic malignancies were observed as follows: 39 (74%), 9 (17%), and 5 (9%).

Conclusion

Our cohort of adult LCH patients demonstrates an unusually high number of additional malignancies. Our study includes predominantly malignancies diagnosed preceding or concurrent with LCH, suggesting a cause of malignancy independent of LCH treatment. Further exploration of the biology of this rare disease may elucidate the mechanism of frequent additional malignancies.

The influence of patient-reported adverse events on Health Utility Score (HUS) and Health-Related Quality of Life (HRQoL) in small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) patients

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Background: The Patient Reported Outcome version of Common-Terminology-Criteria-for-Adverse-Events (PRO-CTCAE) and Edmonton Symptom Assessment System (ESAS) are validated tools that measure toxicities and symptoms in cancer patients. We compared the extent in which the presence and severity of toxicities and symptoms affected HUS in SCLC and NSCLC patients. Methods: Adult SCLC and NSCLC patients were recruited from the Princess Margaret Cancer Centre and surveyed cross-sectionally for clinico-demographic variables, EQ5D-5L, PRO-CTCAE and ESAS. HUS were estimated using EQ5D-5L. PRO-CTCAE toxicities include diarrhea, constipation, decreased appetite, nausea, vomiting, fatigue, neuropathy and rash. ESAS symptoms include pain, tiredness, drowsiness, appetite loss, nausea, shortness of breath, depression, anxiety and lack of well-being. These were combined to show frequency and average severity of toxicities/symptoms per patient. Univariable and multivariable linear regression analyses identified toxicity/symptom influencing HUS. Results: Of 75 SCLC and 150 NSCLC, 52% were male with median age of 65 years. The mean HUS was 0.76 (SCLC = 0.69; NSCLC = 0.79; p = 0.001). Compared to NSCLC, SCLC patients had a significantly higher number of toxicities (3.14 versus 1.33 using PRO-CTCAE, p < 0.0001); symptoms (6.75 vs 5.45 using ESAS, p = 0.0003) and severity of toxicities/symptoms (PRO-CTCAE 0-4: 0.95 versus 0.35, p < 0.0001; ESAS 0-10: 3.37 versus 2.04. p < 0.0001). There were significant correlations between the average severity of toxicities/symptoms and HUS (p < 0.0001) adjusted for age, histology, smoking pack years and performance status. For each increase in the average severity of toxicities, there was a corresponding mean drop of 0.03 in the HUS; for every increase in the average severity of symptoms, the drop was 0.04. These relationships were similar for both SCLC and NSCLC patients. Conclusions: Patient reported toxicities and symptoms have a significant impact on HUS in both SCLC and NSCLC patients. Early and aggressive management of such adverse events may be necessary to improve patients’ HRQoL.

Proton Radiotherapy for Recurrent or Metastatic Head and Neck Cancers with Palliative Quad Shot

Purpose

Some patients with previously treated, unresectable, recurrent or metastatic head and neck malignancies are not amenable to curative-intent treatment. Here, we investigated the quad-shot (RTOG 8502) regimen of hypofractionated proton radiotherapy (RT) in that patient population.

Materials and Methods

From 2013 to 2015, 26 patients with recurrent or metastatic cancers were treated with palliative proton RT to the head and neck with quad shot (3.7 Gy twice daily for 2 days). Patient characteristics and survival data were reviewed.

Results

Seventeen (65%) patients received ≥ 3 quad-shot cycles and 23 (88%) had prior head and neck RT. Overall palliative response was 73% (n = 19). The most common presenting symptom was pain (50%; n = 13), which improved in 85% (n = 22) of all patients. The overall grade-1 acute-toxicity rate was 58% (n = 15), and no acute grade 3 to 5 toxicities were observed.

Conclusions

The proton quad-shot regimen demonstrates favorable palliative response and toxicity profile, even in patients that received prior RT.

Talazoparib Is a Potent Radiosensitizer in Small Cell Lung Cancer Cell Lines and Xenografts

Purpose: Small cell lung cancer (SCLC) is an aggressive malignancy with a critical need for novel therapies. Our goal was to determine whether PARP inhibition could sensitize SCLC cells to ionizing radiation (IR) and if so, to determine the contribution of PARP trapping to radiosensitization.Experimental Design: Short-term viability assays and clonogenic survival assays (CSA) were used to assess radiosensitization in 6 SCLC cell lines. Doses of veliparib and talazoparib with equivalent enzymatic inhibitory activity but differing PARP trapping activity were identified and compared in CSAs. Talazoparib, IR, and their combination were tested in three patient-derived xenograft (PDX) models.Results: Talazoparib radiosensitized 5 of 6 SCLC cell lines in short-term viability assays and confirmed in 3 of 3 cell lines by CSAs. Concentrations of 200 nmol/L talazoparib and 1,600 nmol/L veliparib similarly inhibited PAR polymerization; however, talazoparib exhibited greater PARP trapping activity that was associated with superior radiosensitization. This observation further correlated with an increased number of double-stranded DNA breaks induced by talazoparib as compared with veliparib. Finally, a dose of 0.2 mg/kg talazoparib in vivo caused tumor growth inhibition in combination with IR but not as a single agent in 3 SCLC PDX models.Conclusions: PARP inhibition effectively sensitizes SCLC cell lines and PDXs to IR, and PARP trapping activity enhances this effect. PARP inhibitors, especially those with high PARP trapping activity, may provide a powerful tool to improve the efficacy of radiotherapy in SCLC. Clin Cancer Res; 24(20); 5143-52. ©2018 AACR.

Long-term outcomes in oral cavity squamous cell carcinoma with adjuvant and salvage radiotherapy after surgery

OBJECTIVE

Early-stage oral cavity squamous cell carcinoma (OCSCC) represents a heterogeneous group of patients, and locoregional recurrence rates are as high as 25% with surgery alone. Radiotherapy (RT) is typically reserved as part of salvage multimodality therapy after salvage surgery because it is generally thought that there is no significant detriment to salvage therapy. Our aim was to examine outcomes for recurrent OCSCC treated with salvage surgery and radiation and compare them to outcomes for patients treated with adjuvant postoperative RT upfront.

METHODS

We identified 425 patients with OCSCC treated with postoperative RT at our institution. The 5-year rates of local failure, locoregional failure (LRF), survival, and distant metastasis (DM) were the main outcome measures. We performed a landmark analysis and examined the same outcomes in the adjuvant versus salvage cohorts using Cox proportional hazards and Fine-Gray competing risk method.

RESULTS

The adjuvant cohort had higher tumor (T) (P < 0.0001) and nodal (N) (P < 0.0001) stage than the salvage cohort's stage at initial presentation. On multivariate analysis, a strategy of salvage RT experienced poorer overall survival (OS) compared to upfront adjuvant RT (hazard ratio [HR] 1.84; 95% confidence interval [CI], 1.26-2.70; P = 0.002). Moreover, salvage surgery followed by RT patients experienced increasing risk of LRF (HR 1.56; 95% CI, 1.18-2.06; P = 0.002) and (DM) (HR 1.53; 95% CI, 1.08-2.17; P = 0.02) on multivariate analysis. Additional analysis was performed excluding salvage cohort with advanced disease at initial presentation (T3-T4 and N2). Salvage RT treatment selection for early-stage OCSCC continued to experience significantly poorer OS as compared to adjuvant RT (HR 1.48; 95% CI, 1.002-2.19; P = 0.049).

CONCLUSION

Early-stage OCSCC patients who are observed and experienced recurrence requiring salvage therapy (surgery and RT) have worse oncologic outcomes than locally advanced patients receiving upfront adjuvant RT. Prospective randomized studies are needed to identify high-risk subset of early-stage OCSCC comparing adjuvant RT versus observation, followed by salvage surgery and RT at recurrence.

LEVEL OF EVIDENCE

4. Laryngoscope, 2539-2545, 2018.

Outcome After Radiation Therapy for Langerhans Cell Histiocytosis Is Dependent on Site of Involvement

PURPOSE

To characterize the efficacy and safety of radiation therapy in a contemporary Langerhans cell histiocytosis (LCH) cohort and to explore whether there are sites at higher risk for local recurrence.

PATIENTS AND METHODS

Between 1995 and 2015 we identified 39 consecutive LCH patients who were treated primarily with radiation therapy. Patients were staged by single/multisystem involvement and established risk organ criteria. In 46 irradiated lesions, clinical and radiologic responses were evaluated at multiple time points after radiation therapy. Patient demographics, treatment, and local failure were compared by site of lesion.

RESULTS

Median age at radiation therapy was 35 years (range, 1.5-67 years). Twelve patients had multisystem involvement, and of those, 5 patients had disease in organs considered to be high risk. The following sites were irradiated: bone (31), brain (6), skin (3), lymph node (3), thyroid (2), and nasopharynx (1). Median dose was 11.4 Gy (range, 7.5-50.4 Gy). At a median follow-up of 45 months (range, 6-199 months), local recurrence or progression was noted in 5 of 46 lesions (11%). There were no local failures of the 31 bone lesions evaluated, whereas the 3-year freedom from local failure in the 15 non-bone lesions was 63% (95% confidence interval 32-83%; P=.0008). Local failures occurred in 2 of 3 skin lesions, in 2 of 6 brain lesions, and 1 of 3 lymph node lesions. Deaths were recorded in 5 of 39 patients (13%), all of whom were adults with multisystem disease.

CONCLUSION

Radiation therapy is a safe and effective measure for providing local control of LCH involving the bone. Whereas bone lesions are well controlled with low doses of radiation, disease in other tissues, such as the skin and brain, may require higher doses of radiation or additional treatment modalities.

Unravelling the biology of SCLC: implications for therapy

Small-cell lung cancer (SCLC) is an aggressive malignancy associated with a poor prognosis. First-line treatment has remained unchanged for decades, and a paucity of effective treatment options exists for recurrent disease. Nonetheless, advances in our understanding of SCLC biology have led to the development of novel experimental therapies. Poly [ADP-ribose] polymerase (PARP) inhibitors have shown promise in preclinical models, and are under clinical investigation in combination with cytotoxic therapies and inhibitors of cell-cycle checkpoints.Preclinical data indicate that targeting of histone-lysine N-methyltransferase EZH2, a regulator of chromatin remodelling implicated in acquired therapeutic resistance, might augment and prolong chemotherapy responses. High expression of the inhibitory Notch ligand Delta-like protein 3 (DLL3) in most SCLCs has been linked to expression of Achaete-scute homologue 1 (ASCL1; also known as ASH-1), a key transcription factor driving SCLC oncogenesis; encouraging preclinical and clinical activity has been demonstrated for an anti-DLL3-antibody-drug conjugate. The immune microenvironment of SCLC seems to be distinct from that of other solid tumours, with few tumour-infiltrating lymphocytes and low levels of the immune-checkpoint protein programmed cell death 1 ligand 1 (PD-L1). Nonetheless, immunotherapy with immune-checkpoint inhibitors holds promise for patients with this disease, independent of PD-L1 status. Herein, we review the progress made in uncovering aspects of the biology of SCLC and its microenvironment that are defining new therapeutic strategies and offering renewed hope for patients.

Factors influencing the utilization of prophylactic cranial irradiation in patients with limited-stage small cell lung cancer

Purpose

Brain metastases are common in patients with limited-stage small cell lung cancer (LS-SCLC) due to the inability of most chemotherapeutics to penetrate the blood–brain barrier. Prophylactic cranial irradiation (PCI) is therefore recommended for use in patients with a good response to concurrent chemoradiotherapy. However, PCI is not always delivered; therefore, we investigated the reasons for PCI omission in patients who underwent therapy with curative intent.

Methods and materials

We retrospectively reviewed all patients with LS-SCLC who were treated with curative intent at our institution. Overall survival and cumulative incidence of brain metastasis were estimated by the Kaplan-Meier method. The Pearson χ² test and Mann-Whitney U test were used to examine factors associated with PCI use, and prognostic factors were analyzed with Cox proportional hazards modeling.

Results

We examined 208 patients who were treated for LS-SCLC at our institution. A total of 115 patients (55%) received PCI. The most common documented reason for PCI omission was patient refusal due to neurotoxicity concerns (38%). Physician assessment of being medically unfit (33%) and of advanced age (8%) were the second and third most common reasons, respectively. Karnofsky performance status and clinical American Joint Committee on Cancer stage but not PCI were significantly associated with overall survival. Only clinical stage remained an independent factor on multivariate analysis.

Conclusions

Approximately half of patients with LS-SCLC ultimately receive PCI, generally for guideline-recommended reasons. The most common reason for PCI omission was patient concerns regarding neurotoxicity. Efforts to decrease PCI neurotoxicity, including hippocampal-sparing radiation and memantine use, may increase the use of this survival-improving intervention in eligible patients with LS-SCLC.

Abstract 832: In vitro characterization and clinical correlation of BRCAness as a personalized biomarker for radiosensitization with homologous recombination-directed therapies

Introduction: BRCA1 and BRCA2 are involved in double-strand break (DSBs) repair via homologous recombination (HR). Clinically, BRCA1/2 mutant tumors show sensitivity to cisplatin, a cross-linking agent, but only mild sensitivity to ionizing radiation (IR). The addition of cisplatin to IR has been one of the largest advances in improving patient outcomes with radiotherapy in the past 50 years. Recently, BRCAness has been described wherein sporadic deficits in HR are observed in the absence of germline BRCA1/2 mutations. We hypothesize that BRCAness tumors also exhibit sensitivity to the combination of cisplatin + IR, and are a significant driver of the observed clinical benefit of combination therapy.

Methods: Sensitivity to cisplatin + IR was examined in vitro and correlated with clinical data. Functional HR deficiency (HRD) was assessed in isogenic BRCA1 (H1299; lung) and BRCA2 (DLD1; colon) knockout pairs using 3 assays: the Rad51 foci assay, a flow-based DRGFP assay (DSB reporter assay) and clonogenic survival assays (CSA) with cisplatin +/- IR. Cancer Cell Line Encyclopedia (CCLE) data was used to identify breast cancer cell lines with sporadic, non-BRCA1/2 mutations. Functional HRD in 4 breast cancer cell lines was assessed with the same 3 assays used for the BRCA1/2 isogenic pairs. We also examined 14 triple-negative breast cancer (TNBC) patients treated with neoadjuvant cisplatin + IR. Nine of the 14 had available tissue, which was stained for Rad51 foci.

Results: Functional HRD is observed in the BRCA1/2 isogenic pairs, as demonstrated by the Rad51 foci and DRGFP assay results. Increased sensitivity to cisplatin + IR is observed in the BRCA1/2 knockout lines in CSA results compared to isogenic controls. A genomic scar score, LST (large scale transition), was generated for each line based on CCLE data, with higher LST scores suggesting increased genomic instability and therefore HRD. Four cell lines were selected for further study. Similar functional HRD and cisplatin + IR sensitivity is observed in 2 breast cancer cell lines with high LST scores, as compared to 2 with low LST scores. Epistasis was observed upon siBRCA1 knockdown in the 2 cell lines with high LST scores. Half of the 14 TNBC patients demonstrated pathological complete response to neoadjuvant cisplatin + IR. Nine of the 14 patients had available tissue, of which 4 demonstrated functional HRD by the Rad51 foci assay.

Conclusions: Multiple in vitro assays suggest that HRD tumors are much more sensitive to the widely used combination of cisplatin + IR as compared with HR proficient tumors. Data from our small cohort of triple-negative breast cancer patients appear concordant with these findings. Reliable determination of “BRCAness” tumors should identify a subpopulation of non-germline BRCA1/2-mutated breast cancer patients who may benefit from targeted therapy with cisplatin + IR.

Citation Format: Jennifer Ma, Andrew C. Bell, Jeremy Setton, Justin Haseltine, Marcher Thompson, Rachna Shah, Benjamin H. Lok, Robert Delsite, Rebecca Aft, Nadeem Riaz, Simon Powell. In vitro characterization and clinical correlation of BRCAness as a personalized biomarker for radiosensitization with homologous recombination-directed therapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 832. doi:10.1158/1538-7445.AM2017-832

Identification of effective therapy in Langerhans cell histiocytosis in the adult population

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Background: Langerhans cell histiocytosis (LCH) is a rare disorder of histiocytic proliferation most commonly observed in children. LCH in adults is less characterized and a standard of care has not been established. Here we review clinical outcomes of adult LCH patients (pts) treated with various therapies at a large referral center. Methods: We identified 108 pts over 18 years of age with histologically confirmed LCH presenting to our center between 1990-2015. Clinical and treatment characteristics were examined and classified by single or multi-system involvement (SSI or MSI, respectively) and risk-organ involvement (ROI; liver, spleen, hematopoietic system and CNS). Overall survival (OS) and freedom from first progression (FFFP) were calculated by the Kaplan-Meier method. Univariate analysis was performed with the Cox proportional hazards model. Results: Median age at diagnosis was 44 years (range 18-89) with a median follow-up of 3.9 years (0.1-9.1). Median OS was 16.1 years and FFFP was 5.6 years, with 94 (87%) pts alive at last follow-up. Eighty-three (77%) had SSI and 13 (12%) had ROI. The most common sites of disease were bone (52 pts; 48%), lung (28; 26%), and skin (24; 22%). Only 11 pts (9%) experienced progression of disease (POD) after first treatment. Twenty-four (22%) received radiotherapy, 42 (39%) underwent excision, and 26 (24%) received systemic therapy at any point during treatment. The most common systemic agents were vinblastine, 6-mercaptopurine (6-MP), methotrexate (MTX), and cladribine. Eight received combination vinblastine, 6-MP, and MTX (VMM), 4 of which had MSI. Median progression-free survival (PFS) of VMM pts was 6 months, compared with 2.8 for all other systemic agents (p = 0.1). For OS, lack of ROI was the only significant variable upon univariate analysis (HR .22, 95%CI 0.06-0.75, p = 0.016). No variables were significant for PFS. Conclusions: Effective therapy for adult LCH has not been clearly identified. In our cohort of both low and high risk patients, the low POD rate observed is encouraging. VMM, a regimen previously studied in pediatric pts, is also effective in adults and may be considered the combination of choice for treatment of adult LCH. Further prospective study is warranted.

In vitro functional analysis of HER2 variants in lung cancers to evaluate their oncogenic activity and predict clinical response to HER2 targeted therapies

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Background: HER2 variants are implicated as oncogenic drivers in a variety of cancers. However, not all HER2 variants found on next-generation sequencing (NGS) have been studied, raising the question if these variants of unknown significance (VUS) are oncogenic. This study explores the use of an in-vitro functional assay on HER2 and other variants found on NGS in patients (pts) with lung cancer, and its predictive value for response to HER2 targeted therapy. Methods: Pts with lung cancer at Memorial Sloan Kettering identified to have a HER2 variant by NGS on MSK IMPACT are eligible. NGS data on HER2 variants and co-mutations were analyzed. Functional status was determined by the NovellusDx FACT platform. Mutations were synthesized and transfected into HeLa cells with a fluorescently tagged signaling pathway reporter (MAPK, NFKB, JAK-STAT). Fluorescent microscopy quantified the translocation of reporters to the nucleus, inferring gain of function. Afatinib was added and its effect on pathway activation analyzed. Functional information was correlated with clinical outcomes. Results: As of 2/1/17, 13 pts were included, 9 unique HER2 variants analyzed. Known activating HER2 mutations analyzed (exon 20 insertions (A775_G776insYVMA, G778_P780insGSP, G776delinsVC), point mutations (V659E, L755P, S301F)) showed in vitro gain of function. HER2 VUS analyzed included D277Y showed no gain of function; exon 16 splice variant c.1889 showed gain of function. Afatinib was added to 4 cell lines with gain of function variants (G778_P780insGSP, V659E, L755P, exon 16 splice variant c.1889) all had inhibited pathway activation suggesting in vitro sensitivity to afatinib. Clinically, no response was seen in 2 pts treated with afatinib but more pts are planned to be treated. Objective responses to ado-trastuzumab emtansine (NCT02675829) were seen in 5 pts, all of which had HER2 variants with gain of function. Conclusions: In vitro functional analysis of HER2 variants based on NGS reports is feasible, and has the potential to identify novel actionable oncogenic drivers from VUS. Its predictive value for clinical response to targeted therapy requires further study.

Chemosensitive Relapse in Small Cell Lung Cancer Proceeds through an EZH2-SLFN11 Axis

Small cell lung cancer is initially highly responsive to cisplatin and etoposide but in almost every case becomes rapidly chemoresistant, leading to death within 1 year. We modeled acquired chemoresistance in vivo using a series of patient-derived xenografts to generate paired chemosensitive and chemoresistant cancers. Multiple chemoresistant models demonstrated suppression of SLFN11, a factor implicated in DNA-damage repair deficiency. In vivo silencing of SLFN11 was associated with marked deposition of H3K27me3, a histone modification placed by EZH2, within the gene body of SLFN11, inducing local chromatin condensation and gene silencing. Inclusion of an EZH2 inhibitor with standard cytotoxic therapies prevented emergence of acquired resistance and augmented chemotherapeutic efficacy in both chemosensitive and chemoresistant models of small cell lung cancer.

Challenges and opportunities in primary CNS lymphoma: A systematic review

BACKGROUND

Historically, high-dose methotrexate (HD-MTX) plus consolidation chemotherapy and/or whole brain radiotherapy (WBRT) has been the gold standard on Primary Central Nervous System Lymphoma (PCNSL) management. We sought to examine and summarize the data, on clinical trial (CT) setting, investigating multi-modality treatment to PCNSL.

METHODS

We performed a systematic review of electronic databases (Medline, EMBASE, Cochrane Database and clinicaltrials.gov) and a manual search to identify original PCNSL phase 2 and phase 3 CT from the last 10years. After a 4stage Prisma based selection process, 32 published (3 Randomized CT and 29 phases 2 CT) studies ultimately were selected for review. Four ongoing clinical trials found on clinicaltrial.gov were reviewed. Two investigators reviewed titles, abstracts, and articles independently. Two investigators abstracted data sequentially and evaluated each study independently.

FINDINGS

Treatment of PCNSL requires a multidisciplinary approach. HD-MTX represents the most accepted standard of care induction therapy for newly diagnosed PCNSL. When HD-MTX is given with WBRT for consolidation delayed neurotoxicity can be an important complication, particularly in elderly patients. Studies have suggested that WBRT may be deferred until relapse without compromising survival and deferring WBRT may be the best approach in elderly patients. Results from dose-reduced WBRT and consolidative HD-Ara-C are encouraging. High-dose chemotherapy in combination with autologous stem cell transplantation (HDC-ASCT) as chemotherapy alone has emerged as an important consolidative treatment for selected population. The optimal salvage therapy is still to be defined.

CONCLUSION

WBRT for consolidation is a well-studied modality; however emerging options to selected population such as HDC-ASCT, dose-reduced WBRT or chemotherapy alone are associated with similar survival outcome and less neurotoxicity in selected series. Ongoing and future clinical trials will better define the best approach on this rare disease.

Proton Radiation Therapy for Local Control in a Case of Osteosarcoma of the Neck

A 33-year-old man with symptomatic, unresectable osteosarcoma of the neck experienced disease progression despite treatment with multiple systemic agents. Given the tumor location, adjacent to the spinal cord and encasing the brachial plexus, proton beam therapy was recommended instead of conventional photon radiation therapy. The treatment was delivered in 3 weekly 10 cobalt-gray equivalents fractions, and there was minimal associated toxicity. There has been significant improvement in the patient's presenting symptoms as well as radiologically stable disease at 1 year. A photon intensity-modulated radiation therapy plan was created retrospectively for dosimetric comparison and demonstrated noninferiority, thereby highlighting the need for judicious use of proton therapy in certain cases.

The toxicity and efficacy of concomitant chemoradiotherapy in patients aged 70 years and older with oropharyngeal carcinoma in the intensity-modulated radiotherapy era

BACKGROUND

Despite controversy surrounding its benefit, the use of concomitant chemoradiotherapy (CCRT) in patients with oropharyngeal squamous cell carcinoma (OPSCC) who are aged > 70 years is increasing. However, to the authors' knowledge, few studies to date have compared the outcomes of different systemic treatments in this population.

METHODS

Records from 74 patients aged ≥ 70 years with stage III to stage IVB OPSCC who were undergoing CCRT from 2002 to 2013 at a single institution were reviewed. Patients were stratified according to the systemic therapy received, including cisplatin, carboplatin with either 5-fluorouracil or paclitaxel (CARB), or cetuximab to compare oncologic outcome and toxicity.

RESULTS

The median follow-up was 36 months. The median age of the patients was 75.3 years (range, 70-91 years), with significantly older patients receiving cetuximab (P = .03). A total of 28, 20, and 26 patients, respectively, received CCRT with cisplatin, CARB, and cetuximab. RT interruptions of > 1 day were needed in 4% of patients receiving cisplatin, 20% of patients receiving CARB, and 15% of patients receiving cetuximab (P = .19). Unplanned hospitalizations during CCRT occurred in 25%, 55%, and 58%, respectively, of patients receiving cisplatin, CARB, and cetuximab (P = .03). There were 2 treatment-related deaths, both of which occurred among the patients who were treated with cetuximab. At 5 years, locoregional control was achieved in 100%, 88%, and 60% (P<.001), respectively, and the overall survival rate was 87%, 61%, and 47% (P = .03), respectively, among patients treated with cisplatin, CARB, and cetuximab.

CONCLUSIONS

Toxicity from CCRT remains a challenge for older adults with OPSCC. Herein, the authors found no evidence that this toxicity was mitigated by treatment with cetuximab. Nevertheless, a subset of patients aged ≥70 years appear to tolerate cisplatin-based treatment with acceptable toxicity and excellent outcomes. Further identification of this patient subgroup is crucial to optimize therapy for older patients with OPSCC. Cancer 2017;123:1345-1353. © 2016 American Cancer Society.

PARP Inhibitor Activity Correlates with SLFN11 Expression and Demonstrates Synergy with Temozolomide in Small Cell Lung Cancer

PURPOSE

PARP inhibitors (PARPi) are a novel class of small molecule therapeutics for small cell lung cancer (SCLC). Identification of predictors of response would advance our understanding, and guide clinical application, of this therapeutic strategy.

EXPERIMENTAL DESIGN

Efficacy of PARP inhibitors olaparib, rucaparib, and veliparib, as well as etoposide and cisplatin in SCLC cell lines, and gene expression correlates, was analyzed using public datasets. HRD genomic scar scores were calculated from Affymetrix SNP 6.0 arrays. In vitro talazoparib efficacy was measured by cell viability assays. For functional studies, CRISPR/Cas9 and shRNA were used for genomic editing and transcript knockdown, respectively. Protein levels were assessed by immunoblotting and immunohistochemistry (IHC). Quantitative synergy of talazoparib and temozolomide was determined in vitro In vivo efficacy of talazoparib, temozolomide, and the combination was assessed in patient-derived xenograft (PDX) models.

RESULTS

We identified SLFN11, but not HRD genomic scars, as a consistent correlate of response to all three PARPi assessed, with loss of SLFN11 conferring resistance to PARPi. We confirmed these findings in vivo across multiple PDX and defined IHC staining for SLFN11 as a predictor of talazoparib response. As temozolomide has activity in SCLC, we investigated combination therapy with talazoparib and found marked synergy in vitro and efficacy in vivo, which did not solely depend on SLFN11 or MGMT status.

CONCLUSIONS

SLFN11 is a relevant predictive biomarker of sensitivity to PARP inhibitor monotherapy in SCLC and we identify combinatorial therapy with TMZ as a particularly promising therapeutic strategy that warrants further clinical investigation. Clin Cancer Res; 23(2); 523-35. ©2016 AACR.