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Molecular modifiers of KRAS G12C inhibitor (KRAS G12Ci) efficacy in advanced KRAS G12C-mutant NSCLC are poorly defined. In a large unbiased clinico-genomic analysis of 424 NSCLC patients, we identified and validated co-alterations in KEAP1, SMARCA4 and CDKN2A as major independent determinants of inferior clinical outcomes with KRAS G12Ci monotherapy. Collectively, co-mutations in these three tumor suppressor genes segregated patients into distinct prognostic subgroups and captured ~50% of those with early disease progression (PFS≤3 months) with KRAS G12Ci. Pathway-level integration of less prevalent co-alterations in functionally related genes nominated PI3K/AKT/MTOR pathway and additional baseline RAS gene alterations, including amplifications, as candidate drivers of inferior outcomes with KRAS G12Ci, and revealed a possible association between defective DNA damage response/repair and improved KRAS G12Ci efficacy. Our findings propose a framework for patient stratification and clinical outcome prediction in KRAS G12C-mutant NSCLC that can inform rational selection and appropriate tailoring of emerging combination therapies.

NRG1 rearrangements are oncogenic drivers that are enriched in invasive mucinous adenocarcinomas (IMA) of the lung. The oncoprotein binds ERBB3–ERBB2 heterodimers and activates downstream signaling, supporting a therapeutic paradigm of ERBB3/ERBB2 inhibition. As proof of concept, a durable response was achieved with anti-ERBB3 mAb therapy (GSK2849330) in an exceptional responder with an NRG1-rearranged IMA on a phase I trial (NCT01966445). In contrast, response was not achieved with anti-ERBB2 therapy (afatinib) in four patients with NRG1-rearranged IMA (including the index patient post-GSK2849330). Although in vitro data supported the use of either ERBB3 or ERBB2 inhibition, these clinical results were consistent with more profound antitumor activity and downstream signaling inhibition with anti-ERBB3 versus anti-ERBB2 therapy in an NRG1-rearranged patient-derived xenograft model. Analysis of 8,984 and 17,485 tumors in The Cancer Genome Atlas and MSK-IMPACT datasets, respectively, identified NRG1 rearrangements with novel fusion partners in multiple histologies, including breast, head and neck, renal, lung, ovarian, pancreatic, prostate, and uterine cancers.Significance: This series highlights the utility of ERBB3 inhibition as a novel treatment paradigm for NRG1-rearranged cancers. In addition, it provides preliminary evidence that ERBB3 inhibition may be more optimal than ERBB2 inhibition. The identification of NRG1 rearrangements across various solid tumors supports a basket trial approach to drug development. Cancer Discov; 8(6); 686–95. ©2018 AACR.See related commentary by Wilson and Politi, p. 676.This article is highlighted in the In This Issue feature, p. 663

Table S1

Figures S1, S2, S3, S4, and S5

Supplementary Methods

Supplementary Figure S2 shows that cell lines without NRG1 fusions are insensitive to seribantumab and the IC50 for inhibition of growth of cells by seribantumab.

Supplementary Materials and Methods contains additional details of experimental procedures.

Purpose:Oncogenic fusions involving the neuregulin 1 (NRG1) gene are found in approximately 0.2% of cancers of diverse histologies. The resulting chimeric NRG1 proteins bind predominantly to HER3, leading to HER3-HER2 dimerization and activation of downstream growth and survival pathways. HER3 is, therefore, a rational target for therapy in NRG1 fusion–driven cancers.Experimental Design:We developed novel patient-derived and isogenic models of NRG1-rearranged cancers and examined the effect of the anti-HER3 antibody, seribantumab, on growth and activation of signaling networks in vitro and in vivo.Results:Seribantumab inhibited NRG1-stimulated growth of MCF-7 cells and growth of patient-derived breast (MDA-MB-175-VII, DOC4-NRG1 fusion) and lung (LUAD-0061AS3, SLC3A2-NRG1 fusion) cancer cells harboring NRG1 fusions or NRG1 amplification (HCC-95). In addition, seribantumab inhibited growth of isogenic HBEC cells expressing a CD74-NRG1 fusion (HBECp53-CD74-NRG1) and induced apoptosis in MDA-MB-175-VII and LUAD-0061AS3 cells. Induction of proapoptotic proteins and reduced expression of the cell-cycle regulator, cyclin D1, were observed in seribantumab-treated cells. Treatment of MDA-MB-175-VII, LUAD-0061AS3, and HBECp53-CD74-NRG1 cells with seribantumab reduced phosphorylation of EGFR, HER2, HER3, HER4, and known downstream signaling molecules, such as AKT and ERK1/2. Significantly, administration of seribantumab to mice bearing LUAD-0061AS3 patient-derived xenograft (PDX) and OV-10-0050 (ovarian cancer with CLU-NRG1 fusion) PDX tumors induced regression of tumors by 50%–100%. Afatinib was much less effective at blocking tumor growth.Conclusions:Seribantumab treatment blocked activation of the four ERBB family members and of downstream signaling, leading to inhibition of NRG1 fusion–dependent tumorigenesis in vitro and in vivo in breast, lung, and ovarian patient-derived cancer models.

Supplementary Figures S1-S6, Table S1-S3, and eMethods

Purpose:MET tyrosine kinase inhibitors (TKIs) can achieve modest clinical outcomes in MET exon 14–altered lung cancers, likely secondary to primary resistance. Mechanisms of primary resistance remain poorly characterized and comprehensive proteomic analyses have not previously been performed.Experimental Design:We performed hybrid capture-based DNA sequencing, targeted RNA sequencing, cell-free DNA sequencing, selected reaction monitoring mass spectrometry (SRM-MS), and immunohistochemistry on patient samples of MET exon 14–altered lung cancers treated with a MET TKI. Associations between overall response rate (ORR), progression-free survival (PFS), and putative genomic alterations and MET protein expression were evaluated.Results:Seventy-five of 168 MET exon 14–altered lung cancers received a MET TKI. Previously undescribed (zygosity, clonality, whole-genome duplication) and known (copy-number focality, tumor mutational burden, mutation region/type) genomic factors were not associated with ORR/PFS (P > 0.05). In contrast, MET expression was associated with MET TKI benefit. Only cases with detectable MET expression by SRM-MS (N = 15) or immunochemistry (N = 22) responded to MET TKI therapy, and cancers with H-score ≥ 200 had a higher PFS than cancers below this cutoff (10.4 vs. 5.5 months, respectively; HR, 3.87; P = 0.02).Conclusions:In MET exon 14–altered cancers treated with a MET TKI, a comprehensive analysis of previously unknown and known genomic factors did not identify a genomic mechanism of primary resistance. Instead, MET expression correlated with benefit, suggesting the potential role of interrogating the proteome in addition to the genome in confirmatory prospective trials.

Introduction NRG1 rearrangements produce chimeric ligands that subvert the ERBB pathway to drive tumorigenesis. A better understanding of the signaling networks that mediate transformation by NRG1 fusions is needed to inform effective therapeutic strategies. Unfortunately, this has been hampered by a paucity of patient-derived disease models that faithfully recapitulate this molecularly defined cancer subset. Methods Patient-derived xenograft (PDX) and cell line models were established from NRG1-rearranged lung adenocarcinoma samples. Transcriptomic, proteomic, and biochemical analyses were performed to identify activated pathways. Efficacy studies were conducted to evaluate HER3- and MTOR-directed therapies. Results We established a pair of PDX and cell line models of invasive mucinous lung adenocarcinoma (LUAD) (LUAD-0061AS3, SLC3A2-NRG1), representing the first reported paired in vitro and in vivo model of NRG1-driven tumors. Growth of LUAD-0061AS3 models was reduced by the anti-HER3 antibody GSK2849330. Transcriptomic profiling revealed activation of the MTOR pathway in lung tumor samples with NRG1 fusions. Phosphorylation of several MTOR effectors (S6 and 4EBP1) was higher in LUAD-0061AS3 cells compared with human bronchial epithelial cells and the breast cancer cell line MDA-MB-175-VII (DOC4-NRG1 fusion). Accordingly, LUAD-0061AS3 cells were more sensitive to MTOR inhibitors than MDA-MB-175-VII cells and targeting the MTOR pathway with rapamycin blocked growth of LUAD-0061AS3 PDX tumors in vivo. In contrast, MDA-MB-175-VII breast cancer cells had higher MAPK pathway activation and were more sensitive to MEK inhibition. Conclusions We identify the MTOR pathway as a candidate vulnerability in NRG1 fusion-positive lung adenocarcinoma that may warrant further preclinical evaluation, with the eventual goal of finding additional therapeutic options for patients in whom ERBB-directed therapy fails. Moreover, our results uncover heterogeneity in downstream oncogenic signaling among NRG1-rearranged cancers, possibly tumor type-dependent, the therapeutic significance of which requires additional investigation.

Purpose: Oncogenic fusions involving the neuregulin 1 (NRG1) gene are found in approximately 0.2% of cancers of diverse histologies. The resulting chimeric NRG1 proteins bind predominantly to HER3, leading to HER3-HER2 dimerization and activation of downstream growth and survival pathways. HER3 is, therefore, a rational target for therapy in NRG1 fusion–driven cancers. Experimental Design: We developed novel patient-derived and isogenic models of NRG1-rearranged cancers and examined the effect of the anti-HER3 antibody, seribantumab, on growth and activation of signaling networks in vitro and in vivo. Results: Seribantumab inhibited NRG1-stimulated growth of MCF-7 cells and growth of patient-derived breast (MDA-MB-175-VII, DOC4-NRG1 fusion) and lung (LUAD-0061AS3, SLC3A2-NRG1 fusion) cancer cells harboring NRG1 fusions or NRG1 amplification (HCC-95). In addition, seribantumab inhibited growth of isogenic HBEC cells expressing a CD74-NRG1 fusion (HBECp53-CD74-NRG1) and induced apoptosis in MDA-MB-175-VII and LUAD-0061AS3 cells. Induction of proapoptotic proteins and reduced expression of the cell-cycle regulator, cyclin D1, were observed in seribantumab-treated cells. Treatment of MDA-MB-175-VII, LUAD-0061AS3, and HBECp53-CD74-NRG1 cells with seribantumab reduced phosphorylation of EGFR, HER2, HER3, HER4, and known downstream signaling molecules, such as AKT and ERK1/2. Significantly, administration of seribantumab to mice bearing LUAD-0061AS3 patient-derived xenograft (PDX) and OV-10-0050 (ovarian cancer with CLU-NRG1 fusion) PDX tumors induced regression of tumors by 50%–100%. Afatinib was much less effective at blocking tumor growth. Conclusions: Seribantumab treatment blocked activation of the four ERBB family members and of downstream signaling, leading to inhibition of NRG1 fusion–dependent tumorigenesis in vitro and in vivo in breast, lung, and ovarian patient-derived cancer models.

Background: Irreversible allosteric KRAS p.G12C inhibitors (KG12Ci) such as sotorasib and adagrasib have revolutionized the therapeutic landscape of advanced KG12C-mutant NSCLC, however individual responses are heterogeneous and curtailed by innate and adaptive/acquired resistance. Molecular determinants of KG12Ci efficacy in NSCLC are poorly defined. We dissected the impact of major KG12C co-mutations and explored the effects of less prevalent co-alterations on the clinical activity of KG12Ci in the largest treated cohort to date of patients (pts) with advanced NSCLC. Key findings were validated in preclinical KG12C NSCLC models. Methods: Baseline clinico-genomic features and clinical outcome data from pts with stage IV KG12C NSCLC (ECOG PS 0-2) treated with single-agent KG12Ci were collected retrospectively from 20 centers in the US and Europe. The Kaplan-Meier method was used to estimate PFS and OS and differences were assessed with the log-rank test. Hazard ratios (HR) and their 95% CI were estimated using a Cox proportional hazards model stratified for clinical co-variates. The impact of selected co-alterations on sotorasib efficacy was assessed in syngeneic (C57BL/6) KG12C NSCLC models. Results: 411 eligible pts were included in the study. Median age was 68 years, 77% of pts had received both platinum-based chemotherapy and PD-(L)1 inhibitors and 35% had brain metastases. 83% of pts received sotorasib. ORR with KG12Ci was 32.4% (95% CI, 27.9-37.1), PFS was 5.1m (95% CI, 4.5-5.6) and OS was 10.2m (95% CI, 8.4-12.1). Co-alterations in KEAP1, SMARCA4 and CDKN2A/B were each associated with significantly shorter PFS (KEAP1: 2.8m vs 5.5m, HR 2.50, P Conclusions: Co-mutations in KEAP1, SMARCA4 and CDKN2A/2B define subgroups of KG12C NSCLC pts with markedly distinct outcomes with KG12Ci monotherapy. Tailoring of KG12C inhibitor-anchored therapeutic strategies and patient stratification should take into account the co-mutation status of individual tumors. Citation Format: Marcelo V. Negrao, Haniel A. Araujo, Giuseppe Lamberti, Alissa J. Cooper, Teng Zhou, Neal Akhave, Lukas Delasos, J Kevin Hicks, Mihaela Aldea, Gabriele Minuti, Jacobi Hines, Jacqueline V. Aredo, Michael J. Dennis, Turja Chakrabarti, Susan Scott, Paolo Bironzo, Matthias Scheffler, Petros Christopoulos, So Yeon Kim, Sarah Goldberg, Ying Ni, Blerina Resuli, Lorenza Landi, Shu-Chi Tseng, Mizuki Nishino, Dwight Owen, Collin Blakely, Giannis Mountzios, Catherine A. Shu, Christine Bestvina, Marina Garassino, Kristen Marrone, Jhanelle Gray, Sandip Pravin Patel, Amy L. Cummings, Heather A. Wakelee, Jurgen Wolf, Giorgio V. Scagliotti, Federico Cappuzzo, Fabrice Barlesi, Pradnya Patil, Don L. Gibbons, Funda Meric-Bernstam, J Jack Lee, John V. Heymach, David S. Hong, Rebecca S. Heist, Mark M. Awad, Ferdinandos Skoulidis. Molecular determinants of KRAS p.G12C inhibitor efficacy in advanced NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3431.

Background: More than 50% of patients (pts) with unresectable non-small cell lung cancer (NSCLC) experience relapsed/refractory (R/R) disease within 2 years of starting chemoradiation (CRT) and durvalumab. Based on current national guidelines, these patients are offered treatment for metastatic disease as definitive therapy is no longer feasible. Immunotherapy +/- chemotherapy is typically initiated if a driver-oncogene is absent. The addition of programmed cell death protein-1 (PD-1) antibody pembrolizumab to chemo has resulted in improved progression-free survival (PFS) (8.8 vs 4.9 mos) and overall survival (OS) (69.2% vs 49.4% 12-mos OS) compared to chemotherapy alone. Although this treatment strategy has been incorporated for R/R NSCLC, there remains a paucity of data regarding its efficacy within this population. Here we present clinical outcomes data with pembrolizumab-based regimens for R/R NSCLC following definitive CRT and durvalumab. Methods: This was a retrospective analysis of pts treated between January 2016 to November 2022 at the Cleveland Clinic Foundation in Cleveland, OH. Eligibility criteria included pts age ≥ 18 years with unresectable NSCLC who had received definitive CRT and durvalumab consolidation followed by pembrolizumab for R/R disease. The primary objective was to estimate OS and PFS in this distinct cohort and to compare these findings to historical outcomes. Secondary objective was to compare OS and PFS between specific groups including age, sex, smoking history, combined chemo, histology, KRAS-mutation, and PD-L1 expression. OS and PFS were estimated by Kaplan-Meier method and compared using log rank test. Results: 62 pts were identified, of whom 50 met full eligibility criteria and were included for data analysis. Median follow-up time was 11.3 months (0.7 - 38.2 mos). Median OS was 10.6 months (95% CI; 7.9 mos - NA) with a 1-year OS rate of 48% (95% CI; 35 - 67%). Median PFS was 6.1 months (95% CI; 4.8 - 9.9 mos) with a 1-year PFS rate of 26% (95% CI; 16-45%). Current smokers had significantly better median OS and PFS rates as compared to former smokers (NA vs 10.5 and 9.9 vs 6.0 mos, respectively; P = 0.036 and 0.028). An OS benefit in pts who received chemo with pembrolizumab (median OS 12.9 vs 6.0 mos) was noted but was not statistically significant. No other statistically significant difference was detected. Conclusion: Patients with R/R NSCLC after definitive CRT and durvalumab consolidation represent a distinct cohort with apparent inferior outcomes as compared to those with de novo stage IV disease when treated with pembrolizumab-based therapies. Although improved survival was observed with the addition of chemo to pembrolizumab, further investigation is warranted to optimize treatment strategies for this patient population. Given the limited sample size of our analysis, larger studies with matched real-world treatment cohorts are planned. Citation Format: Lukas Delasos, Wei Wei, Khaled A. Hassan, Nathan Pennell, Pradnya Patil, James Stevenson. Clinical outcomes with pembrolizumab-based therapies in relapsed/refractory NSCLC after definitive chemoradiation and durvalumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6743.

Purpose: MET tyrosine kinase inhibitors (TKIs) can achieve modest clinical outcomes in MET exon 14–altered lung cancers, likely secondary to primary resistance. Mechanisms of primary resistance remain poorly characterized and comprehensive proteomic analyses have not previously been performed. Experimental Design: We performed hybrid capture-based DNA sequencing, targeted RNA sequencing, cell-free DNA sequencing, selected reaction monitoring mass spectrometry (SRM-MS), and immunohistochemistry on patient samples of MET exon 14–altered lung cancers treated with a MET TKI. Associations between overall response rate (ORR), progression-free survival (PFS), and putative genomic alterations and MET protein expression were evaluated. Results: Seventy-five of 168 MET exon 14–altered lung cancers received a MET TKI. Previously undescribed (zygosity, clonality, whole-genome duplication) and known (copy-number focality, tumor mutational burden, mutation region/type) genomic factors were not associated with ORR/PFS (P > 0.05). In contrast, MET expression was associated with MET TKI benefit. Only cases with detectable MET expression by SRM-MS (N = 15) or immunochemistry (N = 22) responded to MET TKI therapy, and cancers with H-score ≥ 200 had a higher PFS than cancers below this cutoff (10.4 vs. 5.5 months, respectively; HR, 3.87; P = 0.02). Conclusions: In MET exon 14–altered cancers treated with a MET TKI, a comprehensive analysis of previously unknown and known genomic factors did not identify a genomic mechanism of primary resistance. Instead, MET expression correlated with benefit, suggesting the potential role of interrogating the proteome in addition to the genome in confirmatory prospective trials.

Primary central nervous system (CNS) marginal zone B‐cell lymphoma (MZBCL) arising from the dural meninges is a rare but indolent disease. This malignancy can present in various ways, hence making it difficult to diagnose. Biopsy results dictate an appropriate treatment plan, which commonly consists of a combination of surgical resection, whole brain radiotherapy and systemic therapy.

Desmoplastic small round cell tumor (DSRCT) is characterized by the t(11;22)(p13;q12) translocation, which fuses the transcriptional regulatory domain of EWSR1 with the DNA-binding domain of WT1, resulting in the oncogenic EWSR1-WT1 fusion protein. The paucity of DSRCT disease models has hampered preclinical therapeutic studies on this aggressive cancer. Here, we developed preclinical disease models and mined DSRCT expression profiles to identify genetic vulnerabilities that could be leveraged for new therapies. We describe four DSRCT cell lines and one patient-derived xenograft model. Transcriptomic, proteomic and biochemical profiling showed evidence of activation of the ERBB pathway. Ectopic expression of EWSR1-WT1 resulted in upregulation of ERRB family ligands. Treatment of DSRCT cell lines with ERBB ligands resulted in activation of EGFR, ERBB2, ERK1/2 and AKT, and stimulation of cell growth. Antagonizing EGFR function with shRNAs, small-molecule inhibitors (afatinib, neratinib) or an anti-EGFR antibody (cetuximab) inhibited proliferation of DSRCT cells. Finally, treatment of mice bearing DSRCT xenografts with a combination of cetuximab and afatinib significantly reduced tumor growth. These data provide a rationale for evaluating EGFR antagonists in patients with DSRCT. This article has an associated First Person interview with the joint first authors of the paper., Summary: Novel models of desmoplastic small round cell tumor (DSRCT) reveal a role for the ERBB pathway in regulating growth of this sarcoma and provide a rationale for evaluating EGFR antagonists in patients with DSRCT.

BACKGROUND AND OBJECTIVES Therapeutic plasma exchange (TPE) is a blood purification treatment capable of removing large molecular weight substances from plasma. It is commonly used for the removal of circulating pathogenic immunoglobulins presumed to be the cause of many autoimmune diseases. TPE can be performed with a membrane-based system (mTPE) or a centrifugal-based system (cTPE). When plasma separation is performed with a membrane, filter clotting can lead to longer treatment time, higher cost and can negatively impact patient satisfaction. In this study, we examine the operational characteristics that might influence filter life. DESIGN, SETTING, PARTICIPANTS, & MEASURES We report on 24 patients, with a total of 135 mTPE treatments in a single tertiary care academic center using the NxStage machine. The study focuses on treatment specific parameters that may lead to procedure failure. The main parameters of interest were transmembrane pressure (TMP) and the filtration fraction as displayed on the machine (FFd) compared to the calculated filtration fraction (FFc). Primary outcome was to measure whether TMP, FFc, and FFd influenced filter survival. Secondary outcomes included factors that might have indirectly resulted in filter failure, including hematocrit (Hct), platelet count, heparin use, and intra-treatment calcium administration. RESULTS In this study, we demonstrated that machine displayed filtration fractions (FFd) were lower than FFc and this difference was significantly larger in TPE sessions that experienced a clotting event (7.58 vs 6.22, P = .031). TPE sessions that clotted had a higher mean TMP (57.48 mmHg vs 44.43 mmHg, P = .001) and clotting events tended to have a lower mean blood flow rate (175.83 mL/min vs 189.55 mL/min, P = .002). In TPE sessions that received prefilter calcium administration, a higher mean dose of calcium gluconate was found in the sessions that experienced clotting (3.27 g vs 2.70 g, P = .013). Patients who experienced at least one clotting event were noted to be heavier than those patients without any clotting events (91.52 kg vs 72.15 kg, P = .040). Prefilter heparin administration was not associated with a lower incidence of filter clotting. We did not find a statistically significant difference in clotting events based upon type of intravenous access, pretreatment hematocrit, or pretreatment platelet counts. CONCLUSION Among patients undergoing mTPE, machine FFd on the NxStage system are consistently lower than FFc. Treatments where there was a greater difference between displayed and FFc had a greater likelihood of filter clotting. Treatments with higher TMP were associated with failed treatments. Prefilter calcium administration during treatment was associated with increased filter clotting. Lower blood flow rates and higher patient weight were also associated with increased filter clotting. Prefilter heparin administration did not reduce the incidence of filter clotting.

The advent of checkpoint inhibitor therapy in medical oncology has led to an increase in hospitalizations for immune-related adverse effects. Severe colitis has been reported in approximately 5% of patients treated with cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) inhibitors, such as ipilimumab. Standard management for those with severe colitis includes administration of systemic corticosteroids with the reservation of antitumor necrosis factor (anti-TNF) therapy, such as infliximab, if there has been no improvement. Rarely, immunotherapy-induced colitis can become life-threatening and result in bowel perforation requiring surgical intervention. Yet, there are no specific recommendations for medical management following colectomy in these situations. In cases of severe colitis from Crohn’s disease, postoperative treatment with infliximab has been found to be safe when administered shortly after intestinal resection. However, there remains limited data to support administration of infliximab following bowel perforation due to immunotherapy-induced colitis. Our case illustrates management of a severe adverse reaction to checkpoint inhibitor therapy and the need to further evaluate the role of infliximab postoperatively in patients who develop colitis complicated by bowel perforation.

8555 Background: Recent changes to the standard of care for unresectable stage III NSCLC include chemoradiation followed by consolidative immunotherapy (IO). Pneumonitis is a well-known complication of radiotherapy (RT) and has been increasingly reported in association with IO. Although rare, pneumonitis can cause severe morbidity and possibly death in extreme cases. Differentiating RT and IO-induced pneumonitis (RTP vs IOP) is crucial for acute management and future considerations of individualized treatment. However, the clinical and radiological features of RTP and IOP may be similar and often indistinguishable on computed tomography (CT). Texture-based CT radiomics has previously been used to distinguish benign and malignant nodules on lung CT. In this study, we explore if radiomic features extracted from lung CT can distinguish between RTP and IOP. Methods: From 236 patients with stage III NSCLC who underwent chemoradiation followed by consolidative durvalumab, we identified 110 cases of treatment-related pneumonitis. IOP cases were identified through a retrospective review of electronic medical records and independently verified by a thoracic oncologist using features such as bilateral lung involvement, inflammatory changes outside the field of RT, temporal relationship to IO, and response to treatment. Inflammatory lesions were manually annotated using Slicer 3D. After excluding cases without discernible cause and non-identifiable lung lesions (n = 61), we included 49 cases in the study (RTP n = 20; IOP n = 29). A total of 555 features from Gabor, Laws, Laplace, and Haralick feature families were extracted on a pixel level from post-treatment CT images. A support vector machine (SVM) classifier was trained with the most discriminating features identified by Wilcoxon rank-sum test feature selection method. The classifier performance for distinguishing RTP vs. IOP was assessed by averaging the area under the receiver operating characteristic curve (AUC) values computed over 100 iterations of threefold cross-validation. Results: We identified the top 5 radiomic texture features distinguishing RTP from IOP including Haralick entropy, Haralick info, Laws median, and high- and low-frequency Gabor. Using 3-fold cross-validation, the SVM classifier model built on the radiomic features achieved an AUC of 0.83 (95% confidence interval, 0.78 - 0.86). Conclusions: Pneumonitis is a severe complication of both RT and IO that must be taken into consideration when evaluating future risks of IO-based therapies. The distinction between RTP and IOP remains challenging based on CT findings alone. Radiomic texture features analysis of post-treatment CT images can potentially differentiate RTP from IOP in stage III NSCLC patients who received RT followed by consolidative durvalumab. Additional multi-site independent validation of these quantitative image-based biomarkers is warranted.

Multi-kinase RET inhibitors, such as cabozantinib and RXDX-105, are active in lung cancer patients with RET fusions; however, the overall response rates to these two drugs are unsatisfactory compared to other targeted therapy paradigms. Moreover, these inhibitors may have different efficacies against RET rearrangements depending on the upstream fusion partner. A comprehensive preclinical analysis of the efficacy of RET inhibitors is lacking due to a paucity of disease models harboring RET rearrangements. Here, we generated two new patient-derived xenograft (PDX) models, one new patient-derived cell line, one PDX-derived cell line, and several isogenic cell lines with RET fusions. Using these models, we re-examined the efficacy and mechanism of action of cabozantinib and found that this RET inhibitor was effective at blocking growth of cell lines, activating caspase 3/7 and inhibiting activation of ERK and AKT. Cabozantinib treatment of mice bearing RET fusion-positive cell line xenografts and two PDXs significantly reduced tumor proliferation without adverse toxicity. Moreover, cabozantinib was effective at reducing growth of a lung cancer PDX that was not responsive to RXDX-105. Transcriptomic analysis of lung tumors and cell lines with RET alterations showed activation of a MYC signature and this was suppressed by treatment of cell lines with cabozantinib. MYC protein levels were rapidly depleted following cabozantinib treatment. Taken together, our results demonstrate that cabozantinib is an effective agent in preclinical models harboring RET rearrangements with three different 5′ fusion partners (CCDC6, KIF5B and TRIM33). Notably, we identify MYC as a protein that is upregulated by RET expression and downregulated by treatment with cabozantinib, opening up potentially new therapeutic avenues for the combinatorial targetin of RET fusion- driven lung cancers. The novel RET fusion-dependent preclinical models described here represent valuable tools for further refinement of current therapies and the evaluation of novel therapeutic strategies., Summary: Establishment of four patient-derived models of RET fusion-positive lung adenocarcinomas with three different RET fusions shows that MYC expression is regulated by RET.

Desmoplastic small round cell tumor (DSRCT) is characterized by the t(11;22)(p13;q12) chromosomal translocation, which fuses the transcriptional regulatory domain of EWSR1 with the zinc finger DNA-binding domain of WT1, resulting in the oncogenic transcription factor EWS-WT1. DSRCT primarily affects young males and has a 5-year overall survival of about 15%. Typical treatment approaches for patients with DSRCT involve a multi-modal combination of surgery, chemotherapy and radiation. The paucity of DSRCT disease models has hampered functional and pre-clinical therapeutic studies in this aggressive cancer. Here, we developed robust preclinical disease models and mined DSRCT expression profiling data to identify genetic vulnerabilities that could be leveraged for the identification of rational therapies. Specifically, we developed four new DSRCT cell lines and one patient-derived xenograft (PDX) model. Transcriptomic and proteomic profiling showed evidence of activation of the ERBB pathway. Ectopic expression of EWSR1-WT1 resulted in upregulation of ERRB family ligands and downstream signaling. Treatment of DSRCT cell lines with ERBB ligands resulted in activation of EGFR, ERBB2, ERK1/2 and AKT, and stimulation of cell growth. Conversely, targeting of EGFR using shRNA, small molecule inhibitors (afatinib, neratinib) or an anti-EGFR antibody (cetuximab) inhibited growth and induced apoptosis in DSRCT cells. Finally, treatment of mice bearing DSRCT xenografts with a combination of cetuximab and afatinib significantly reduced tumor growth. These data provide a rationale for the clinical evaluation of EGFR antagonists in patients with DSRCT.

BACKGROUND. Oncogenic fusions involving the neuregulin 1 (NRG1) gene are found in approximately 0.2% of cancers of diverse histologies. The resulting chimeric NRG1 proteins bind predominantly to HER3, leading to HER3-HER2 dimerization and activation of downstream growth and survival pathways. HER3 is therefore a rational target for therapy in NRG1 fusion-driven cancers. METHODS. We developed novel patient-derived and isogenic models of NRG1-rearranged cancers and examined the effect of the anti-HER3 antibody, seribantumab, on growth and activation of signaling networks in vitro and in vivo. RESULTS. Seribantumab inhibited NRG1-stimulated growth of MCF-7 cells and growth of patient-derived breast (MDA-MB-175-VII, DOC4-NRG1) and lung (LUAD-0061AS3, SLC3A2-NRG1 fusion) cancer cells harboring NRG1 fusions or NRG1 amplification (HCC-95). In addition, seribantumab inhibited growth of isogenic HBEC cells expressing a CD74-NRG1 fusion (HBECp53-CD74-NRG1) and induced apoptosis in MDA-MB-175-VII and LUAD-0061AS3 cells. Induction of pro-apoptotic proteins and reduced expression of the cell cycle regulator cyclin D1 were observed in seribantumab-treated cells. Treatment of MDA-MB-175-VII, LUAD-0061AS3 and HBECp53-CD74-NRG1 cells with seribantumab, reduced phosphorylation of EGFR, HER2, HER3, HER4 and known downstream signaling molecules such as AKT and ERK1/2. Significantly, administration of seribantumab to mice bearing LUAD-0061AS3 PDX and OV-10–0050 (ovarian cancer with CUL-NRG1 fusion) PDX tumors induced regression of tumors by 50–100%. Afatinib was much less effective at blocking tumor growth. CONCLUSION. Seribantumab treatment blocked activation of the four ERBB family members and of downstream signaling, leading to inhibition of NRG1 fusion-dependent tumorigenesis in vitro and in vivo in breast, lung and ovarian patient-derived cancer models.

Introduction Immune-checkpoint inhibitors have become an increasingly popular form of systemic therapy for cancer treatment. Their use has proven to be so effective that certain regimens have gained approval as first-line therapy for various solid tumor types. The most common and well-studied forms of immunotherapy include agents that target cytotoxic T-lymphocyte antigen-4, programmed death-1, and programmed death ligand-1. These therapies act by blocking signaling between immune cells and cancer cells which subsequently augment T cell-mediated destruction of tumor cells. Case report Here, we report a case of a 77-year-old black male with no history of or risk factors for diabetes mellitus who presented with acute onset of diabetic ketoacidosis after beginning immunotherapy with nivolumab for metastatic high-grade neuroendocrine tumor of the lung. He was admitted and treated for diabetic ketoacidosis but required prolonged use of an insulin infusion with frequent need of intravenous dextrose due to labile blood sugars. The patient was eventually discharged and discontinued further immunotherapy with nivolumab. Discussion Due to the unique mechanisms by which immune-checkpoint inhibitors cause immune-mediated destruction of tumor cells, clinicians may be challenged with their associated autoimmune complications referred to as immune-related adverse events. In particular, the incidence of endocrine dysfunction following immune-checkpoint inhibitor therapy is approximately 12%, with the development of insulin-dependent diabetes mellitus being a rare complication. Increasing awareness of immune-related adverse events is essential for the early recognition and effective management of patients who present with life-threatening complications related to immune-checkpoint inhibitor therapy.

Bing-Neel syndrome (BNS) remains a rare complication of Waldenstrom Macroglobulinemia. Given the paucity of this disease, treatment guidelines are based on small clinical trials with limited participants. Here we present a case of BNS that developed while on ibrutinib therapy, followed by a review of the next steps in management.

Primary bone lymphoma (PBL) is a subtype of lymphoma that exclusively affects skeletal tissue. Despite the relatively common involvement of skeletal structures as a manifestation of non-Hodgkin’s lymphoma (NHL), primary and exclusive involvement of the skeletal system is rare. The prevalence of PBL is estimated to be 3–7% amongst primary bone tumors and less than 2% amongst all lymphomas in adults. However, the definition of primary bone lymphoma has been inconsistent over time. Within our institution, we identified four cases of primary bone lymphoma based on diagnostic criteria formed from the general consensus of multiple organizations, including the World Health Organization (WHO) and International Extranodal Lymphoma Study Group (IELSG). Here, we discuss the distinct characteristics amongst these cases in addition to performing a systematic review of current literature regarding this lymphoproliferative entity.

NRG1 rearrangements are oncogenic drivers that are enriched in invasive mucinous adenocarcinomas (IMA) of the lung. The oncoprotein binds ERBB3–ERBB2 heterodimers and activates downstream signaling, supporting a therapeutic paradigm of ERBB3/ERBB2 inhibition. As proof of concept, a durable response was achieved with anti-ERBB3 mAb therapy (GSK2849330) in an exceptional responder with an NRG1-rearranged IMA on a phase I trial (NCT01966445). In contrast, response was not achieved with anti-ERBB2 therapy (afatinib) in four patients with NRG1-rearranged IMA (including the index patient post-GSK2849330). Although in vitro data supported the use of either ERBB3 or ERBB2 inhibition, these clinical results were consistent with more profound antitumor activity and downstream signaling inhibition with anti-ERBB3 versus anti-ERBB2 therapy in an NRG1-rearranged patient-derived xenograft model. Analysis of 8,984 and 17,485 tumors in The Cancer Genome Atlas and MSK-IMPACT datasets, respectively, identified NRG1 rearrangements with novel fusion partners in multiple histologies, including breast, head and neck, renal, lung, ovarian, pancreatic, prostate, and uterine cancers. Significance: This series highlights the utility of ERBB3 inhibition as a novel treatment paradigm for NRG1-rearranged cancers. In addition, it provides preliminary evidence that ERBB3 inhibition may be more optimal than ERBB2 inhibition. The identification of NRG1 rearrangements across various solid tumors supports a basket trial approach to drug development. Cancer Discov; 8(6); 686–95. ©2018 AACR. See related commentary by Wilson and Politi, p. 676. This article is highlighted in the In This Issue feature, p. 663

Fusions involving RET receptor tyrosine kinase are a common driver of tumors across different tissue types, such as lung, thyroid, colorectal, soft tissue and others. TAS0953/HM06 (hereby referred to as HM06) is a novel 2ndgeneration RET-specific inhibitor that is effective against RET solvent front (G810) and gatekeeper (V804) mutations. Here, we evaluated the efficacy of HM06 in lung and thyroid carcinomas, and soft-tissue sarcoma cell lines and PDXs derived from RET inhibitor-naive tumor samples or from tumors with acquired resistance to selpercatinib. HM06 was more effective than the RET multi-kinase inhibitors cabozantinib and vandetanib, and as effective as selpercatinib and pralsetinib in inhibiting growth of patient-derived and isogenic lung, thyroid and sarcoma cell lines (IC50=0.02-0.1 µM) harboring different RET fusions (KIF5B-RET, CCDC6-RET, TRIM33-RET, SPECCL1-RET) or activating mutations (RET C634W). Growth of non-tumor cells was up to 80-fold less sensitive to HM06 (IC50= 1.6 µM). Treatment of RET fusion-positive lung cancer cells with HM06 resulted in a dose-dependent inhibition of RET phosphorylation (Y905 and Y1062) and the downstream effectors AKT, ERK1/2, p70S6K and S6. Caspase 3/7 activity and markers of apoptosis (BIM, cleaved PARP) were induced by HM06 to a similar extent as pralsetinib and selpercatinib (dose range: 0.05-1 µM). HM06 induced changes in the core mediators of cell cycle regulation (upregulation of p27, downregulation of CCND1) and suppressed expression of MYC and ETV5. In vivo, HM06 blocked tumor growth and/or induced regression of up to 65% in seven patient-derived xenograft (PDX) models with RET fusions (five NSCLC PDXs, one sarcoma PDX and one NSCLC cell-line xenograft) to a similar extent as pralsetinib and selpercatinib. However, 6 weeks after cessation of treatment of the SPECCL1-RET-driven sarcoma PDX model, growth of tumors treated with HM06 was suppressed completely, whereas 3/5 pralsetinib-treated tumors and 1/5 selpercatinib-treated tumor regrew. Combination of HM06 and the MET inhibitor capmatinib effectively blocked growth of PDX tumors in a model that was derived from a patient sample that expressed RET fusion and METamplification, and was resistant to selpercatinib. These results suggest that HM06 may be an effective therapy for RET-driven tumors in a tissue-type agnostic manner and can effectively address common on-target and off-target resistance mechanisms such as RET G810X and V804X mutations. HM06 is currently in a phase 1 and 2 clinical trial for patients with advanced solid tumors with RET gene abnormalities (margaRET, NCT 04683250). Citation Format: Igor Odintsov, Renate I. Kurth, Kota Ishizawa, Lukas Delasos, Allan J.W. Lui, Inna Khodos, Connor J. Hagen, Qing Chang, Marissa S. Mattar, Morana Vojnic, Siddharth Kunte, Annalisa Bonifacio, Claudio Giuliano, Elisa De Stanchina, Emily Cheng, Emanuela Lovati, Marc Ladanyi, Romel Somwar. TAS0953/HM06 is effective in preclinical models of diverse tumor types driven by RET alterations [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P233.

BACKGROUND RET rearrangements are targetable, oncogenic lung cancer drivers. While previous series have shown durable clinical benefit with pemetrexed-based therapies in ALK- and ROS1-rearranged lung cancers, the benefits of pemetrexed-based treatments in patients with RET-rearranged lung cancers relative to other genomic subsets have not previously been explored. PATIENTS AND METHODS A retrospective review of patients with pathologically confirmed stage IIIB/IV lung adenocarcinomas and evidence of a RET, ROS1, or ALK rearrangement, or a KRAS mutation was conducted. Patients were eligible if they received treatment with pemetrexed alone or in combination. The primary outcome of progression-free survival (PFS), and secondary outcomes of overall response rate (ORR, RECIST v1.1), time to progression (TTP), and time to treatment discontinuation were compared between RET-rearranged and groups of ROS1-rearranged, ALK-rearranged, and KRAS-mutant lung cancers. RESULTS We evaluated 104 patients. Patients with RET-rearranged lung cancers (n = 18) had a median PFS of 19 months [95% confidence interval (CI) 12-not reached (NR)] that was comparable with patients with ROS1- (23 months, 95% CI 14-NR, n = 10) and ALK-rearranged (19 months, 95% CI 15-36, n = 36) lung cancers, and significantly improved compared with patients with KRAS-mutant lung cancers (6 months, 95% CI 5-9, P < 0.001, n = 40). ORR (45%), median TTP (20 months, 95% CI 17-NR), and median time to treatment discontinuation (21 months, 95% CI 6-NR) in patients with RET-rearranged lung cancers were not significantly different compared with patients with ALK- and ROS1-rearranged lung cancers, and improved compared with patients with KRAS-mutant lung cancers. CONCLUSION Durable benefits with pemetrexed-based therapies in RET-rearranged lung cancers are comparable with ALK- and ROS1-rearranged lung cancers. When selecting therapies for patients with RET-rearranged lung cancers, pemetrexed-containing regimens should be considered.

245 Background: Despite low-dose computed tomography (LDCT) screening for lung cancer recommended by the United States Preventive Services Task Force (USPSTF) demonstrating a relative reduction in mortality, there remains low rates of testing nationwide. Yet studies are limited regarding specific differences in screening rates amongst various outpatient care settings. Methods: We performed retrospective chart reviews of patients followed by resident providers within an academic internal medicine residency program who met USPSTF guidelines for lung cancer screening between 2015-2020. This was conducted at three separate outpatient clinic sites including a state-funded academic institution, inner city community health center, and veteran affairs medical center. Data collection included patient demographic and smoking histories as well as rates of ordered and completed LDCT screening. Results: A total of 832 patients were identified as current or former smokers between the ages of 55 and 80 years: 320 from Hartford Hospital Community Health Center (HHCHC), 262 from University of Connecticut Health Center (UCHC), and 250 from the Veteran Affairs (VA) Medical Center. 85 (27%) of these patients from HHCHC, 84 (32%) from UCHC, and 56 (22%) from the VA met USPSTF eligibility criteria for LDCT screening. Overall compliance rates of screening were found to be 44% at HHCHC, 59.5% at UCHC, and 51.8% at the VA. Results are outlined in Table. Conclusions: Screening rates for lung cancer with LDCT remain low but have been steadily improving throughout the United States following new recommendations and increased awareness provided by multiple medical organizations. We sought to compare differences in compliance rates amongst various outpatient clinics within the same internal medicine residency program at University of Connecticut. Our findings demonstrate significant differences in LDCT screening for lung cancer between the program’s community health center versus its state and federally funded outpatient clinics. Automatic reminders to providers can potentially improve rates of lung cancer screening. Patients should also be educated about the importance of screening to improve adherence with imaging. [Table: see text]

9006 Background: MET exon 14 alterations comprise a novel class of lung cancer drivers. MET tyrosine kinase inhibitors (TKIs) are active in patients with these cancers, but objective response rates (ORRs) are modest (~30%-40%). A subset of these cancers may harbor intrinsic resistance. Moreover, patients with initial benefit invariably develop acquired resistance. We set out to identify potential resistance mechanisms. Methods: We studied patients with stage IV MET exon 14-altered lung cancers who received a MET TKI. When feasible, tumor and/or plasma samples were collected, prioritizing paired pre- and post-TKI collection. Tumor samples underwent targeted mass spectrometry analysis (Nantomics) and DNA- (including MSK-IMPACT)/RNA-based (MSK-Fusion) next-generation sequencing (NGS). Plasma cfDNA underwent targeted NGS. ORR and progression-free survival (PFS) were assessed (RECIST v1.1). Results: 74 patients received a MET TKI (1 TKI n = 55; ≥2 TKIs n = 19). 91% received crizotinib as their 1st TKI. Pre-TKI MET levels in tumor tissue (range 0-2120 amol/µg) were associated with outcomes: ORR 63% (n = 7/11) and median PFS 6.9 mos with detectable MET vs ORR 0% (n = 0/5) and median PFS 4.6 mos with undetectable MET (HR for PFS 0.3). Pre-TKI RAS pathway activation was associated with response: ORR 0% (n = 0/6) with KRAS/NF1/RASA1 mutation vs ORR 29% (n = 25/87) in others. Similar outcomes were observed with pre-TKI KRAS expression (n = 16, all with detectable KRAS levels): ORR 0% (n = 0/2) in KRAS ≥700 amol/µg vs ORR 50% (n = 7/14) < 700 amol/µg. Acquired resistance (Jackman criteria) was seen in 29 patients, 9 with paired pre-/post-treatment samples. On-target acquired resistance was found in 2/9 patients (22%): MET D1228N (n = 1), HGF amplification (n = 1). Potential off-target acquired resistance mechanisms were found in 5/9 pts (44%): KRAS G13V (n = 1), RASA1 S742* (n = 1), MDM2 amplification (n = 2), EGFR amplification (n = 1). Conclusions: Lack of MET expression or RAS pathway activation is associated with poor MET TKI outcomes in MET exon14-altered lung cancers. On-target acquired resistance is found in < 25% of patients; HGF amplification is a novel mechanism. Off-target intrinsic/acquired resistance may be mediated by RAS/MDM2/EGFR pathway activation.

11583 Background: Lung cancers driven by oncogenic RET fusions have lower response rates to targeted monotherapy such as cabozantinib (28%) relative to response rates typically observed in ALK- or ROS1- rearranged lung adenocarcinomas (60-80%). Methods: To identify targetable co-dependencies or cooperating pathways for RET fusion-positive lung cancers, we performed high-throughput chemical and genetic screens to find FDA-approved drugs or genes that when inhibited, would synergize with cabozantinib in RET fusion-positive lung cancer cell lines. In addition we performed NGS of a pair of pre-treatment and post-cabozantinib progression samples. Results: We identified EGFR siRNAs and anti-EGFR drugs as synergistic with cabozantinib. Combinations of drugs that target EGFR (cetuximab, afatinib, erlotinib, gefitinib, neratinib) and RET (cabozantinib, CEP-32496, lenvatinib, vandetanib) were more effective at reducing growth of RET cell lines than any single agent in vitro and in xenograft models. Cabozantinib treatment of RET fusion-positive cell lines inhibited EGFR and RET phosphorylation, an observation not seen in RET wild-type cell lines. Co-immunoprecipitation studies reveal that RET and EGFR interact. Ectopic expression of CCDC6-RET in NIH-3T3 or human bronchial epithelial cells resulted in upregulation of multiple ERBB receptors and ligands (not seen in a ROS1 fusion-positive cell line) and a concomitant increase in EGFR stability. Treatment with ERBB pathway ligands or overexpression of EGFR decreased sensitivity to cabozantinib in two RET fusion-positive cell lines. Finally, sequencing of a pair of pre-treatment and post-progression samples from a lung cancer patient treated with cabozantinib revealed acquired amplification of EGFR in the latter sample. Conclusions: Taken together, these results suggest that the tumorigenic potential of RET fusion oncogenes is dependent on deregulation of ERBB-activated pathways and that a combination of RET and EGFR drugs could be more effective in treating RET fusion-positive tumors. Moreover, amplification of EGFR is a potential driver of resistance to cabozantinib in RET-rearranged lung cancers.