Safety profile of pembrolizumab monotherapy based on an aggregate safety evaluation of 8937 patients

BACKGROUND

Pembrolizumab has a manageable safety profile as described in its label, which was primarily based on 2799 patients who participated in clinical trials for melanoma or non-small cell lung cancer. Here, we evaluated the safety of pembrolizumab in a broader population of patients from 31 advanced cancer clinical trials across 19 cancer types.

METHODS

Safety was analyzed in patients who received at least one dose of pembrolizumab (200 mg every 3 weeks [Q3W], 10 mg/kg Q2W or Q3W, or 2 mg/kg Q3W). Adverse events (AEs) and immune-mediated AEs and infusion reactions were evaluated.

RESULTS

Safety data from 8937 patients in 31 trials of pembrolizumab monotherapy were pooled (median, seven administrations; range, 1-59). Median duration on treatment was 4.1 months (range, 0.03-40.1). AEs occurred in 96.6% of patients. Grade 3-5 AEs occurred in 50.6% of patients. AEs led to pembrolizumab discontinuation in 12.7% of patients and death in 5.9%. Immune-mediated AEs and infusion reactions occurred in 23.7% of patients (4.6% experienced multiple immune-mediated AEs/infusion reactions) and led to pembrolizumab discontinuation in 3.6% and death in 0.2%. Grade 3-5 immune-mediated AEs occurred in 6.3% of patients. Serious immune-mediated AEs and infusion reactions occurred in 6.0% of patients. Median time to immune-mediated AE onset was 85 days (range, 13-163). Of 2657 immune-mediated AEs, 22.3% were initially treated with prednisone ≥ 40 mg/day or equivalent, and 8.3% were initially treated with lower steroid doses.

CONCLUSIONS

This pooled analysis of 31 clinical trials showed that pembrolizumab has a consistent safety profile across indications.

Integration of peripheral blood- and tissue-based biomarkers of response to immune checkpoint blockade in urothelial carcinoma

As predictive biomarkers of response to immune checkpoint inhibitors (ICIs) remain a major unmet clinical need in patients with urothelial carcinoma (UC), we sought to identify tissue-based immune biomarkers of clinical benefit to ICIs using multiplex immunofluorescence and to integrate these findings with previously identified peripheral blood biomarkers of response. Fifty-five pretreatment and 12 paired on-treatment UC specimens were identified from patients treated with nivolumab with or without ipilimumab. Whole tissue sections were stained with a 12-plex mIF panel, including CD8, PD-1/CD279, PD-L1/CD274, CD68, CD3, CD4, FoxP3, TCF1/7, Ki67, LAG-3, MHC-II/HLA-DR, and pancytokeratin+SOX10 to identify over three million cells. Immune tissue densities were compared to progression-free survival (PFS) and best overall response (BOR) by RECIST version 1.1. Correlation coefficients were calculated between tissue-based and circulating immune populations. The frequency of intratumoral CD3+ LAG-3+ cells was higher in responders compared to nonresponders (p = 0.0001). LAG-3+ cellular aggregates were associated with response, including CD3+ LAG-3+ in proximity to CD3+ (p = 0.01). Exploratory multivariate modeling showed an association between intratumoral CD3+ LAG-3+ cells and improved PFS independent of prognostic clinical factors (log HR -7.0; 95% confidence interval [CI] -12.7 to -1.4), as well as established biomarkers predictive of ICI response (log HR -5.0; 95% CI -9.8 to -0.2). Intratumoral LAG-3+ immune cell populations warrant further study as a predictive biomarker of clinical benefit to ICIs. Differences in LAG-3+ lymphocyte populations across the intratumoral and peripheral compartments may provide complementary information that could inform the future development of multimodal composite biomarkers of ICI response. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Infigratinib in Early-Line and Salvage Therapy for FGFR3-Altered Metastatic Urothelial Carcinoma

The optimal sequencing of systemic treatments for metastatic urothelial cancer (mUC) is unknown. We assessed the efficacy of infigratinib, a fibroblast growth factor receptor (FGFR) 1 to 3 inhibitor, in 67 patients with FGFR3-altered mUC by line of therapy. Objective response rates were 31% (early-line setting) and 24% (≥2nd-line setting). Infigratinib has notable activity in mUC regardless of line of therapy.

Clinical and Morphologic Characteristics of Fibroblast Growth Factor Receptor Inhibitor-Associated Retinopathy

Importance

Fibroblast growth factor receptor (FGFR) 1 to 4 inhibitors are approved by the US Food and Drug Administration and suppress the mitogen-activated protein kinase (MAPK) pathway, with a potential for treatment-related retinopathy. To date, implications of FGFR inhibitor-associated ocular toxic effects are poorly described. Therefore, more detailed clinical descriptions of this ocular toxic effect could help explain visual symptoms while receiving drug therapy.

Objective

To describe the clinical and morphologic characteristics of serous retinal disturbances associated with FGFR inhibitors.

Design, Setting, and Participants

In this retrospective case series, 146 patients receiving FGFR inhibitors as cancer treatment at a single tertiary referral center were included. This study included 40 eyes of 20 patients with retinopathy by optical coherence tomography (OCT). OCTs were obtained on the remaining patients and the results were judged normal. Patients were recruited from March 2012 to January 2021.

Main Outcomes and Measures

Characteristics of treatment-emergent choroidal and retinal OCT abnormalities as compared with baseline OCT, associated with visual acuity at presentation and at fluid resolution.

Results

A total of 20 of 146 patients (13.7%) exhibited FGFR inhibitor-associated retinopathy. Of these 20 patients, 11 (55%) were female, and the median (range) age was 62.6 (42.7-86.0) years. The median (range; mean) time from medication start to initial subretinal fluid detection was 21 (5-125; 32) days. The median (interquartile range [IQR]) baseline logMAR best-corrected visual acuity (BCVA) was 0 (0-0.1). At fluid accumulation, 11 eyes had decreased vision: the median (IQR) subgroup baseline BCVA was 0 (0-0.1); and the median (IQR) BCVA change from baseline to accumulation was -0.1 (-0.2 to -0.1). For 26 eyes (65%) with follow-up, the subretinal fluid resolved without medical intervention or drug interruption in all but 1 patient. At fluid resolution, the median (IQR) BCVA was 0.1 (0-0.1), and the change in median (IQR) BCVA from baseline to fluid resolution was 0 (-0.03 to 0). No patient discontinued drug therapy on account of their retinopathy.

Conclusions and Relevance

FGFR inhibitors result in subretinal fluid foci similar to other drugs that inhibit the MAPK pathway. In this series, FGFR inhibitors did not cause irreversible loss of vision; the retinopathy was self-limited and did not require medical intervention. These results may explain visual symptoms while taking the drug, although the precise frequency or magnitude of this adverse effect cannot be determined with certainty from this retrospective investigation.

Pretreatment Eosinophil Counts in Patients With Advanced or Metastatic Urothelial Carcinoma Treated With Anti-PD-1/PD-L1 Checkpoint Inhibitors

Eosinophils influence antitumor immunity and may predict response to treatment with immune checkpoint inhibitors (ICIs). To examine the association between blood eosinophil counts and outcomes in patients with advanced or metastatic urothelial carcinoma (mUC) treated with ICIs, we identified 2 ICI-treated cohorts: discovery (n=60) and validation (n=111). Chemotherapy cohorts were used as comparators (first-line platinum-based chemotherapy, n=75; second-line or more pemetrexed, n=77). The primary endpoint was overall survival (OS). Secondary endpoints were time on treatment (ToT) and progression-free survival. Univariate and multivariate analyses were performed using Cox proportional hazard models. Associations between changes in eosinophil count at weeks 2/3 and 6 after the start of ICI treatment were analyzed using landmark analyses. Baseline characteristics of the ICI cohorts were similar. In the discovery cohort, an optimal cutoff for pretreatment eosinophil count was determined [Eos-Lo: <100 cells/µL; n=9 (15%); Eos-Hi: ≥100 cells/µL; n=51 (85%)]. Eos-Lo was associated with inferior outcomes [OS: hazard ratio (HR), 3.98; 95% confidence interval (CI), 1.85-8.56; P<0.013; ToT: HR, 2.45; 95% CI, 1.17-5.10; P=0.017]. This was confirmed in the validation cohort [Eos-Lo: n=17 (15%); Eos-Hi: n=94 (85%)] (OS: HR, 2.51; 95% CI, 1.31-4.80; P=0.006; ToT: HR, 2.22; 95% CI, 1.2-3.80; P=0.004), and remained significant after adjustment for other prognostic factors. Changes in eosinophil counts at weeks 2/3 and 6 were not clearly associated with outcomes. In chemotherapy cohorts, eosinophil counts were not associated with outcomes. In conclusion, low pretreatment eosinophil count was associated with poorer outcomes in patients with mUC treated with ICIs, and may represent a new predictive biomarker.

Tumor fraction-guided cell-free DNA profiling in metastatic solid tumor patients

BACKGROUND

Cell-free DNA (cfDNA) profiling is increasingly used to guide cancer care, yet mutations are not always identified. The ability to detect somatic mutations in plasma depends on both assay sensitivity and the fraction of circulating DNA in plasma that is tumor-derived (i.e., cfDNA tumor fraction). We hypothesized that cfDNA tumor fraction could inform the interpretation of negative cfDNA results and guide the choice of subsequent assays of greater genomic breadth or depth.

METHODS

Plasma samples collected from 118 metastatic cancer patients were analyzed with cf-IMPACT, a modified version of the FDA-authorized MSK-IMPACT tumor test that can detect genomic alterations in 410 cancer-associated genes. Shallow whole genome sequencing (sWGS) was also performed in the same samples to estimate cfDNA tumor fraction based on genome-wide copy number alterations using z-score statistics. Plasma samples with no somatic alterations detected by cf-IMPACT were triaged based on sWGS-estimated tumor fraction for analysis with either a less comprehensive but more sensitive assay (MSK-ACCESS) or broader whole exome sequencing (WES).

RESULTS

cfDNA profiling using cf-IMPACT identified somatic mutations in 55/76 (72%) patients for whom MSK-IMPACT tumor profiling data were available. A significantly higher concordance of mutational profiles and tumor mutational burden (TMB) was observed between plasma and tumor profiling for plasma samples with a high tumor fraction (z-score≥5). In the 42 patients from whom tumor data was not available, cf-IMPACT identified mutations in 16/42 (38%). In total, cf-IMPACT analysis of plasma revealed mutations in 71/118 (60%) patients, with clinically actionable alterations identified in 30 (25%), including therapeutic targets of FDA-approved drugs. Of the 47 samples without alterations detected and low tumor fraction (z-score<5), 29 had sufficient material to be re-analyzed using a less comprehensive but more sensitive assay, MSK-ACCESS, which revealed somatic mutations in 14/29 (48%). Conversely, 5 patients without alterations detected by cf-IMPACT and with high tumor fraction (z-score≥5) were analyzed by WES, which identified mutational signatures and alterations in potential oncogenic drivers not covered by the cf-IMPACT panel. Overall, we identified mutations in 90/118 (76%) patients in the entire cohort using the three complementary plasma profiling approaches.

CONCLUSIONS

cfDNA tumor fraction can inform the interpretation of negative cfDNA results and guide the selection of subsequent sequencing platforms that are most likely to identify clinically-relevant genomic alterations.

Randomized Phase III Trial of Gemcitabine and Cisplatin With Bevacizumab or Placebo in Patients With Advanced Urothelial Carcinoma: Results of CALGB 90601 (Alliance)

PURPOSE

The combination of gemcitabine and cisplatin (GC) is a standard therapy for metastatic urothelial carcinoma. Based on data that angiogenesis plays a role in urothelial carcinoma growth and progression, a randomized placebo-controlled trial was performed with the primary objective of testing whether patients treated with GC and bevacizumab (GCB) have superior overall survival (OS) than patients treated with GC and placebo (GCP).

PATIENTS AND METHODS

Between July 2009 and December 2014, 506 patients with metastatic urothelial carcinoma without prior chemotherapy for metastatic disease and no neoadjuvant or adjuvant chemotherapy within 12 months were randomly assigned to receive either GCB or GCP. The primary end point was OS, with secondary end points of progression-free survival, objective response, and toxicity.

RESULTS

With a median follow-up of 76.3 months among alive patients, the median OS was 14.5 months for patients treated with GCB and 14.3 months for patients treated with GCP (hazard ratio for death = 0.87; 95% CI, 0.72 to 1.05; two-sided stratified log-rank P = .14). The median progression-free survival was 8.0 months for GCB and 6.7 months for GCP (hazard ratio = 0.77; 95% CI, 0.63 to 0.95; P = .016). The proportion of patients with grade 3 or greater adverse events did not differ significantly between both arms, although increased bevacizumab-related toxicities such as hypertension and proteinuria occurred in the bevacizumab-treated arm.

CONCLUSION

The addition of bevacizumab to GC did not result in improved OS. The observed median OS of about 14 months is consistent with prior phase III trials of cisplatin-based chemotherapy.

Cancer therapy shapes the fitness landscape of clonal hematopoiesis

Acquired mutations are pervasive across normal tissues. However, understanding of the processes that drive transformation of certain clones to cancer is limited. Here we study this phenomenon in the context of clonal hematopoiesis (CH) and the development of therapy-related myeloid neoplasms (tMNs). We find that mutations are selected differentially based on exposures. Mutations in ASXL1 are enriched in current or former smokers, whereas cancer therapy with radiation, platinum and topoisomerase II inhibitors preferentially selects for mutations in DNA damage response genes (TP53, PPM1D, CHEK2). Sequential sampling provides definitive evidence that DNA damage response clones outcompete other clones when exposed to certain therapies. Among cases in which CH was previously detected, the CH mutation was present at tMN diagnosis. We identify the molecular characteristics of CH that increase risk of tMN. The increasing implementation of clinical sequencing at diagnosis provides an opportunity to identify patients at risk of tMN for prevention strategies.

Hyperphosphatemia Secondary to the Selective Fibroblast Growth Factor Receptor 1-3 Inhibitor Infigratinib (BGJ398) Is Associated with Antitumor Efficacy in Fibroblast Growth Factor Receptor 3-altered Advanced/Metastatic Urothelial Carcinoma

BACKGROUND

Infigratinib (BGJ398) is a potent, selective fibroblast growth factor receptor (FGFR) 1-3 inhibitor with significant activity in metastatic urothelial carcinoma (mUC) bearing FGFR3 alterations. It can cause hyperphosphatemia due to the "on-target" class effect of FGFR1 inhibition.

OBJECTIVE

To investigate the relationship between hyperphosphatemia and treatment response in patients with mUC.

INTERVENTION

Oral infigratinib 125 mg/d for 21 d every 28 d.

DESIGN, SETTING, AND PARTICIPANTS

Data from patients treated with infigratinib in a phase I trial with platinum-refractory mUC and activating FGFR3 alterations were retrospectively analyzed for clinical efficacy in relation to serum hyperphosphatemia. The relationship between plasma infigratinib concentration and phosphorous levels was also assessed.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Clinical outcomes were compared in groups with/without hyperphosphatemia.

RESULTS AND LIMITATIONS

Of the 67 patients enrolled, 48 (71.6%) had hyperphosphatemia on one or more laboratory tests. Findings in patients with versus without hyperphosphatemia were the following: overall response rate 33.3% (95% confidence interval [CI] 20.4-48.4) versus 5.3% (95% CI 0.1-26.0); disease control rate 75.0% (95% CI 60.4-86.4) versus 36.8% (95% CI 16.3-61.6). This trend was maintained in a 1-mo landmark analysis. Pharmacokinetic/pharmacodynamic analysis showed that serum phosphorus levels and physiologic infigratinib concentrations were correlated positively. Key limitations include retrospective design, lack of comparator, and limited sample size.

CONCLUSIONS

This is the first published study to suggest that hyperphosphatemia caused by FGFR inhibitors, such as infigratinib, can be a surrogate biomarker for treatment response. These findings are consistent with other reported observations and will need to be validated further in a larger prospective trial.

PATIENT SUMMARY

Targeted therapy is a new paradigm in treating bladder cancer. In a study using infigratinib, a drug that targets mutations in a gene called fibroblast growth factor receptor 3 (FGFR3), we found that elevated levels of phosphorous were associated with greater clinical benefit. In the future, these data may help inform treatment strategies.

Abstract 5703: Oncologic therapy shapes the fitness landscape of clonal hematopoiesis

Recent studies among healthy individuals show evidence of somatic mutations in leukemia-associated genes, referred to as clonal hematopoiesis (CH). To determine the relationship between CH and oncologic therapy we collected sequential blood samples from 525 cancer patients (median sampling interval time = 23 months, range: 6-53 months) of whom 61% received cytotoxic therapy or external beam radiation therapy and 39% received either targeted/immunotherapy or were untreated. Samples were sequenced using deep targeted capture-based platforms. To determine whether CH mutational features were associated with tMN risk, we performed Cox proportional hazards regression on 9,549 cancer patients exposed to oncologic therapy of whom 75 cases developed tMN (median time to transformation=26 months). To further compare the genetic and clonal relationships between tMN and the proceeding CH, we analyzed 35 cases for which paired samples were available. We compared the growth rate of the variant allele fraction (VAF) of CH clones across treatment modalities and in untreated patients. A significant increase in the growth rate of CH mutations was seen in DDR genes among those receiving cytotoxic (p=0.03) or radiation therapy (p=0.02) during the follow-up period compared to patients who did not receive therapy. Similar growth rates among treated and untreated patients were seen for non-DDR CH genes such as DNMT3A. Increasing cumulative exposure to cytotoxic therapy (p=0.01) and external beam radiation therapy (2x10-8) resulted in higher growth rates for DDR CH mutations. Among 34 subjects with at least two CH mutations in which one mutation was in a DDR gene and one in a non-DDR gene, we studied competing clonal dynamics for multiple gene mutations within the same patient. The risk of tMN was positively associated with CH in a known myeloid neoplasm driver mutation (HR=6.9, p&lt;10-6), and increased with the total number of mutations and clone size. The strongest associations were observed for mutations in TP53 and for CH with mutations in spliceosome genes (SRSF2, U2AF1 and SF3B1). Lower hemoglobin, lower platelet counts, lower neutrophil counts, higher red cell distribution width and higher mean corpuscular volume were all positively associated with increased tMN risk. Among 35 cases for which paired samples were available, in 19 patients (59%), we found evidence of at least one of these mutations at the time of pre-tMN sequencing and in 13 (41%), we identified two or more in the pre-tMN sample. In all cases the dominant clone at tMN transformation was defined by a mutation seen at CH Our serial sampling data provide clear evidence that oncologic therapy strongly selects for clones with mutations in the DDR genes and that these clones have limited competitive fitness, in the absence of cytotoxic or radiation therapy. We further validate the relevance of CH as a predictor and precursor of tMN in cancer patients. We show that CH mutations detected prior to tMN diagnosis were consistently part of the dominant clone at tMN diagnosis and demonstrate that oncologic therapy directly promotes clones with mutations in genes associated with chemo-resistant disease such as TP53.

Citation Format: Kelly L. Bolton, Ryan N. Ptashkin, Teng Gao, Lior Braunstein, Sean M. Devlin, Minal Patel, Antonin Berthon, Aijazuddin Syed, Mariko Yabe, Catherine Coombs, Nicole M. Caltabellotta, Mike Walsh, Ken Offit, Zsofia Stadler, Choonsik Lee, Paul Pharoah, Konrad H. Stopsack, Barbara Spitzer, Simon Mantha, James Fagin, Laura Boucai, Christopher J. Gibson, Benjamin Ebert, Andrew L. Young, Todd Druley, Koichi Takahashi, Nancy Gillis, Markus Ball, Eric Padron, David Hyman, Jose Baselga, Larry Norton, Stuart Gardos, Virginia Klimek, Howard Scher, Dean Bajorin, Eder Paraiso, Ryma Benayed, Maria Arcilla, Marc Ladanyi, David Solit, Michael Berger, Martin Tallman, Montserrat Garcia-Closas, Nilanjan Chatterjee, Luis Diaz, Ross Levine, Lindsay Morton, Ahmet Zehir, Elli Papaemmanuil. Oncologic therapy shapes the fitness landscape of clonal hematopoiesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5703.

Long-Term Outcomes in KEYNOTE-052: Phase II Study Investigating First-Line Pembrolizumab in Cisplatin-Ineligible Patients With Locally Advanced or Metastatic Urothelial Cancer

PURPOSE

The phase II single-arm KEYNOTE-052 study evaluated the efficacy and safety of first-line pembrolizumab for patients with locally advanced or metastatic cisplatin-ineligible urothelial carcinoma (UC).

PATIENTS AND METHODS

Three hundred seventy patients received pembrolizumab 200 mg intravenously every 3 weeks for up to 24 months. Positive tumor programmed death ligand 1 (PD-L1) expression was defined as combined positive score (CPS) ≥ 10. Response was assessed by independent central review every 9 weeks per RECIST v1.1. The primary end point was objective response rate (ORR).

RESULTS

At data cutoff (September 26, 2018), the minimum follow-up was 2 years since the last patient enrolled. ORR was 28.6% (95% CI, 24.1% to 33.5%); 33 patients (8.9%) and 73 patients (19.7%) achieved complete and partial response, respectively. The median duration of response was 30.1 months (95% CI, 18.1 months to not reached [NR]); responses lasted ≥ 12 and ≥ 24 months in 67% and 52% of patients, respectively. Forty patients with complete or partial response completed 2 years of study treatment, and 32 had ongoing response at completion. Median overall survival (OS) was 11.3 months (95% CI, 9.7 to 13.1 months), and 12- and 24-month OS rates were 46.9% and 31.2%, respectively. In patients with CPS ≥ 10, ORR was 47.3% (95% CI, 37.7% to 57.0%) and median OS was 18.5 months (95% CI, 12.2 to 28.5 months). In patients with lymph node-only disease, ORR was 49.0% (95% CI, 34.8% to 63.4%), and median OS was 27.0 months (12.4 months to NR). There were no new safety signals.

CONCLUSION

First-line pembrolizumab confers meaningful and durable clinical response in cisplatin-ineligible patients with advanced UC and is associated with prolonged OS, particularly with PD-L1 CPS ≥ 10 and lymph node-only disease.

Infigratinib in upper tract urothelial carcinoma versus urothelial carcinoma of the bladder and its association with comprehensive genomic profiling and/or cell-free DNA results

BACKGROUND

Infigratinib (BGJ398) is a potent and selective fibroblast grown factor receptor 1 to 3 (FGFR1-3) inhibitor with significant activity in patients with advanced or metastatic urothelial carcinoma bearing FGFR3 alterations. Given the distinct biologic characteristics of upper tract urothelial carcinoma (UTUC) and urothelial carcinoma of the bladder (UCB), the authors examined whether infigratinib had varying activity in these settings.

METHODS

Eligible patients had metastatic urothelial carcinoma with activating FGFR3 mutations and/or fusions. Comprehensive genomic profiling was performed on formalin-fixed, paraffin-embedded tissues. Blood was collected for cell-free DNA analysis using a 600-gene panel. Patients received infigratinib at a dose of 125 mg orally daily (3 weeks on/1 week off) until disease progression or intolerable toxicity occurred. The overall response rate (ORR; partial response [PR] plus complete response [CR]) and disease control rate (DCR; CR plus PR plus stable disease [SD]) were characterized.

RESULTS

A total of 67 patients were enrolled; the majority (70.1%) had received ≥2 prior antineoplastic therapies. In 8 patients with UTUC, 1 CR and 3 PRs were observed (ORR, 50%); the remaining patients achieved a best response of SD (DCR, 100%). In patients with UCB, 13 PRs were observed (ORR, 22%), and 22 patients had a best response of SD (DCR, 59.3%). Notable differences in genomic alterations between patients with UTUC and those with UCB included higher frequencies of FGFR3-TACC3 fusions (12.5% vs 6.8%) and FGFR3 R248C mutations (50% vs 11.9%), and a lower frequency of FGFR3 S249C mutations (37.5% vs 59.3%).

CONCLUSIONS

Differences in the cumulative genomic profile were observed between patients with UTUC and those with UCB in the current FGFR3-restricted experience, underscoring the distinct biology of these diseases. These results support a planned phase 3 adjuvant study predominantly performed in this population.

Abstract LB-304: Oncologic therapy for solid tumors alters the risk of clonal hematopoiesis

Solid tumor patients often suffer from cytopenias and are at risk for therapy-related myeloid neoplasms (tMN). Somatic mutations in leukemia-associated genes can occur in normal healthy individuals, referred to as clonal hematopoiesis (CH). CH is associated with cytopenias, risk of leukemia and cardiovascular disease. We and others have shown that CH is frequent in cancer patients. Characterization of the relationship between exposure to specific oncologic regimens and CH and how these relate to cytopenias and tMN risk would inform treatment decisions and tMN prevention strategies.

To determine the relationship between CH and oncologic therapy we interrogated CH in a cohort of 9045 solid tumor patients. Subjects were sequenced using a targeted panel of cancer-associated mutations used to screen tumor samples against a blood control sample. Mutation detection was performed on blood-derived sequencing data using the matched tumor as a comparator and accounted for background sequencing error rates.

CH was identified in 23% of patients. In multivariate regression analyses adjusted by age, CH was more often found in current smokers (OR=1.20, 95%CI=1.07-1.35, p&lt;0.001) and less often found in Asians compared to Whites (OR=0.72, 95%CI=0.56-0.89, p&lt;0.001). Smoking was associated with CH mutations in ASXL1 (OR=3.75, 95%CI=2.73-5.17, p&lt;0.001). There was a higher proportion of patients with CH among those who had received chemotherapy (OR=1.14, 95%CI=1.02-1.26, p=0.02) and those who had received external beam radiation therapy (OR=1.45, 95%CI=1.28-1.63, p&lt;0.001) prior to blood collection. Mutations in the DNA repair/cell cycle pathway (including TP53, PPM1D and CHEK2) were more common among patients who received chemotherapy and radiation therapy prior to IMPACT testing compared to those who were treatment naïve (p&lt;0.001). Exposure to prior cytotoxic chemotherapy (OR=1.20, 95%CI=1.02-1.30; p=0.007) and radiation therapy (OR=1.6, 95%CI=1.4-1.9, p&lt;0.001) was associated with having CH while exposure to immunotherapy and targeted therapy was not. Increasing cumulative dose of chemotherapy overall and cytotoxic therapy was associated with a higher likelihood of CH (p=0.015 and p=0.007 respectively). There was evidence of specific gene, treatment and dosage effects. To further examine the relationship between oncologic therapy and clonal evolution of CH, we collected 375 sequential samples at least 18 months apart. T mean change in VAF of CH mutations per year was found to increase by 0.17% in patients who did not receive further therapy during the follow-up time and 0.49% in those who were exposed to cytotoxic chemotherapy. A subset of patients with CH were consented to germline testing for cancer predisposition genes (N=6368). We observe a higher rate of CH among patients with a germline mutation in the cell cycle/DNA repair pathway (i.e. TP53) when compared to patients without germline mutations (OR=3.7, 95% CI: 1.35-9.35, p-value=0.01).

CH is frequent in solid tumor patients and can be reliably detected when a matched tumor normal targeted gene sequencing approach is performed. Beyond age, CH is strongly associated with race, smoking and importantly prior exposure to oncologic therapy with evidence of specific treatment effects. Screening of CH in cancer cohorts is critical to the development of future clinical guidelines and risk-adapted prevention strategies for tMN.

Note: This abstract was not presented at the meeting.

Citation Format: Kelly Bolton, Ryan Ptashkin, Lior Braunstein, Teng Gao, Sean M. Devlin, Daniel Kelly, Catherine Coombs, Minal Patel, Matahi Moarii, Elsa Bernard, Antonin Berthon, Laura Boucai, Dominik Glodzik, Axel Martin, Zsofia Stadler, Michael Walsh, Diana Mandelker, Akshar Patel, Jessica Schulman, Gunes Gundem, Aijazuddin Syed, Maria Arcila, David B. Solit, Mark E. Robson, Marc Ladanyi, Choonsik Lee, John Philip, Dean Bajorin, Montserrat Garcia-Closas, Stuart Gardos, David Hyman, Martin Tallman, Mariko Yabe, Kenneth Offit, Howard Scher, Virginia Klimek, Luis Diaz, Nilanjan Chatterjee, Michael F. Berger, Lindsay Morton, Ross Levine, Ahmet Zehir, Elli Papaemmanuil. Oncologic therapy for solid tumors alters the risk of clonal hematopoiesis [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 LB-304.

Microsatellite Instability Is Associated With the Presence of Lynch Syndrome Pan-Cancer

PURPOSE

Microsatellite instability (MSI) and/or mismatch repair deficiency (MMR-D) testing has traditionally been performed in patients with colorectal (CRC) and endometrial cancer (EC) to screen for Lynch syndrome (LS)-associated cancer predisposition. The recent success of immunotherapy in high-frequency MSI (MSI-H) and/or MMR-D tumors now supports testing for MSI in all advanced solid tumors. The extent to which LS accounts for MSI-H across heterogeneous tumor types is unknown. Here, we establish the prevalence of LS across solid tumors according to MSI status.

METHODS

MSI status was determined using targeted next-generation sequencing, with tumors classified as MSI-H, MSI-indeterminate, or microsatellite-stable. Matched germline DNA was analyzed for mutations in LS-associated mismatch repair genes ( MLH1, MSH2, MSH6, PMS2, EPCAM). In patients with LS with MSI-H/I tumors, immunohistochemical staining for MMR-D was assessed.

RESULTS

Among 15,045 unique patients (more than 50 cancer types), LS was identified in 16.3% (53 of 326), 1.9% (13 of 699), and 0.3% (37 of 14,020) of patients with MSI-H, MSI-indeterminate, and microsatellite-stable tumors, respectively ( P < .001). Among patients with LS with MSI-H/I tumors, 50% (33 of 66) had tumors other than CRC/EC, including urothelial, prostate, pancreas, adrenocortical, small bowel, sarcoma, mesothelioma, melanoma, gastric, and germ cell tumors. In these patients with non-CRC/EC tumors, 45% (15 of 33) did not meet LS genetic testing criteria on the basis of personal/family history. Immunohistochemical staining of LS-positive MSI-H/I tumors demonstrated MMR-D in 98.2% (56 of 57) of available cases.

CONCLUSION

MSI-H/MMR-D is predictive of LS across a much broader tumor spectrum than currently appreciated. Given implications for cancer surveillance and prevention measures in affected families, these data support germline genetic assessment for LS for patients with an MSI-H/MMR-D tumor, regardless of cancer type or family cancer history.

ERCC2 Helicase Domain Mutations Confer Nucleotide Excision Repair Deficiency and Drive Cisplatin Sensitivity in Muscle-Invasive Bladder Cancer

PURPOSE

DNA-damaging agents comprise the backbone of systemic treatment for many tumor types; however, few reliable predictive biomarkers are available to guide use of these agents. In muscle-invasive bladder cancer (MIBC), cisplatin-based chemotherapy improves survival, yet response varies widely among patients. Here, we sought to define the role of the nucleotide excision repair (NER) gene ERCC2 as a biomarker predictive of response to cisplatin in MIBC.

EXPERIMENTAL DESIGN

Somatic missense mutations in ERCC2 are associated with improved response to cisplatin-based chemotherapy; however, clinically identified ERCC2 mutations are distributed throughout the gene, and the impact of individual ERCC2 variants on NER capacity and cisplatin sensitivity is unknown. We developed a microscopy-based NER assay to profile ERCC2 mutations observed retrospectively in prior studies and prospectively within the context of an institution-wide tumor profiling initiative. In addition, we created the first ERCC2-deficient bladder cancer preclinical model for studying the impact of ERCC2 loss of function.

RESULTS

We used our functional assay to test the NER capacity of clinically observed ERCC2 mutations and found that most ERCC2 helicase domain mutations cannot support NER. Furthermore, we show that introducing an ERCC2 mutation into a bladder cancer cell line abrogates NER activity and is sufficient to drive cisplatin sensitivity in an orthotopic xenograft model.

CONCLUSIONS

Our data support a direct role for ERCC2 mutations in driving cisplatin response, define the functional landscape of ERCC2 mutations in bladder cancer, and provide an opportunity to apply combined genomic and functional approaches to prospectively guide therapy decisions in bladder cancer.See related commentary by Grivas, p. 907.

Clinical Outcome of Retroperitoneal Lymph Node Dissection after Chemotherapy in Patients with Pure Embryonal Carcinoma in the Orchiectomy Specimen

OBJECTIVE

To determine the pathologic findings and clinical outcome of patients with pure embryonal carcinoma (EC) of the testis who were diagnosed with testis cancer from January 1989 to January 2013 who underwent an orchiectomy, cisplatin-based chemotherapy and a postchemotherapy retroperitoneal lymph node dissection (PC-RPLND).

METHODS

We compared those patients with 100% EC with those with mixed nonseminomatous germ cell tumor pathology who underwent a PC-RPLND.

RESULTS

Of 1105 patients who underwent a PC-RPLND, 145 had pure EC. Twenty-six percent of patients presented with metastatic disease outside the retroperitoneum. Patients with mixed histologies tended to have worse International Germ Cell Cancer Collaborative Group risk compared to those with EC at orchiectomy (P = .037). Histology at PC-RPLND revealed fibrosis or necrosis in 76%, mature teratoma in 19% and viable cancer in 4%. Over one-third of the patients had a residual mass of <1 cm prior to RPLND; of whom 15% harbored mature teratoma in PC-RPLND histology. The Kaplan-Meier estimated probability of recurrence at 5 years of follow-up was 3.1% (95% CI 1.2%, 8.0%) for EC histology, 7.3% lower than mixed histology. For cancer-specific mortality, the Kaplan-Meier estimated probability at 5 years was 4.6% (95% CI 3.3%, 6.3%) and 1.7% (95% CI 0.4%, 6.8%) for mixed and pure EC histologies, respectively.

CONCLUSION

Approximately 20% of patients with pure EC had teratoma at PC-RPLND. We have shown that those with a maximum node size of <1 cm should not be precluded from RPLND.

First-line pembrolizumab in cisplatin-ineligible patients with locally advanced and unresectable or metastatic urothelial cancer (KEYNOTE-052): a multicentre, single-arm, phase 2 study

BACKGROUND

More than half of all patients with advanced urothelial cancer cannot receive standard, first-line cisplatin-based chemotherapy because of renal dysfunction, poor performance status, or other comorbidities. We assessed the activity and safety of first-line pembrolizumab in cisplatin-ineligible patients with locally advanced and unresectable or metastatic urothelial cancer.

METHODS

In this multicentre, single-arm, phase 2 study (KEYNOTE-052), cisplatin-ineligible patients with advanced urothelial cancer who had not been previously treated with systemic chemotherapy were recruited from 91 academic medical centres in 20 countries. Enrolled patients received intravenous pembrolizumab 200 mg every 3 weeks. The primary endpoint was objective response (the proportion of patients who achieved complete or partial response) in all patients and by PD-L1 expression status according to the Response Evaluation Criteria in Solid Tumors, version 1.1, as assessed by independent central review. PD-L1 expression was assessed in tumour and inflammatory cells from tumour biopsies provided at study entry. Activity and safety were analysed in all patients who received at least one dose of pembrolizumab (all-patients-treated population). This study is registered with ClinicalTrials.gov, number NCT02335424, and follow-up is ongoing.

FINDINGS

Between Feb 24, 2015, and Aug 8, 2016, 374 patients were enrolled and 370 patients received at least one dose of pembrolizumab. 89 (24%, 95% CI 20-29) of 370 patients had a centrally assessed objective response, and as of Sept 1, 2016 (data cutoff), 74 (83%) of 89 responses were ongoing. Median follow-up was 5 months (IQR 3·0-8·6). A PD-L1-expression cutoff of 10% was associated with a higher frequency of response to pembrolizumab; 42 (38%, 95% CI 29-48) of 110 patients with a combined positive score of 10% or more had a centrally assessed objective response. The most common grade 3 or 4 treatment-related adverse events were fatigue (eight [2%] of 370 patients), alkaline phosphatase increase (five [1%]), colitis, and muscle weakness (both four [1%]). 36 (10%) of 370 patients had a serious treatment-related adverse event. 17 (5%) of 370 patients died from non-treatment-related adverse events associated with death, and one patient died from treatment-related adverse events (myositis in addition to grade 3 thyroiditis, grade 3 hepatitis, grade 3 pneumonia, and grade 4 myocarditis).

INTERPRETATION

First-line pembrolizumab has antitumour activity and acceptable tolerability in cisplatin-ineligible patients with urothelial cancer, most of whom were elderly, had poor prognostic factors, or had serious comorbidities. In view of this result, pembrolizumab has become a new treatment option for patients who are cisplatin-ineligible or not suitable candidates for chemotherapy. Pembrolizumab in the first-line setting is being further assessed in the phase 3 KEYNOTE-361 trial (ClinicalTrials.gov, NCT02335424).

FUNDING

Merck & Co.

Bilateral Testicular Germ Cell Tumors in the Era of Multimodal Therapy

OBJECTIVE

To characterize the incidence, presentation, management, and relapse of a large population of bilateral testicular germ cell tumors (TGCT) from a single institution.

PATIENTS AND METHODS

We identified bilateral TGCT diagnosed between January 1989 and February 2014. We categorized synchronous and metachronous TGCT, noting time between first and second TGCT, histology (seminoma vs nonseminoma [NSGCT]), stage, and treatments. Kaplan-Meier survival estimates characterized relapse.

RESULTS

Of 5132 patients with TGCT, 128 (2.5%) had bilateral TGCT. Bilateral TGCT increased over time-1.7% in 1989-1994 up to 3.8% in 2010 to February 2014. The 35 (27%) synchronous cases of TGCT had 20 (57%) concordant seminoma, 5 (14%) concordant NSGCT, and 10 (29%) discordant NSGCT. The 93 (73%) metachronous cases had median time interval to second TGCT of 73 months (range: 5 months-28.6 years). Compared with first TGCT, 39 (42%) had discordant histology, 29 (31%) had concordant seminoma, and 25 (27%) had concordant NSGCT. Stage at first tumor was statistically similar to second TGCT (second stage I, II, II in 69%, 22%, 10%). Increasing duration between first and second TGCT was not associated with higher stage (II or III) at second TGCT (P = .09). Treatment at first tumor was not associated with stage at second tumor. Relapse following bilateral diagnosis was 16.8% (95% confidence interval 10.5%-26.2%) at 5 years.

CONCLUSION

Incidence of bilateral TGCT increased with >25% of metachronous TGCT presenting ≥10 years after first TGCT; possible causes include increased survivorship and referral bias. Stage was statistically similar at first and second tumor; stage at second tumor was not associated with time interval between tumors or prior treatment modality at first tumor.

Atezolizumab in patients with locally advanced and metastatic urothelial carcinoma who have progressed following treatment with platinum-based chemotherapy: a single-arm, multicentre, phase 2 trial

BACKGROUND

Patients with metastatic urothelial carcinoma have few treatment options after failure of platinum-based chemotherapy. In this trial, we assessed treatment with atezolizumab, an engineered humanised immunoglobulin G1 monoclonal antibody that binds selectively to programmed death ligand 1 (PD-L1), in this patient population.

METHODS

For this multicentre, single-arm, two-cohort, phase 2 trial, patients (aged ≥18 years) with inoperable locally advanced or metastatic urothelial carcinoma whose disease had progressed after previous platinum-based chemotherapy were enrolled from 70 major academic medical centres and community oncology practices in Europe and North America. Key inclusion criteria for enrolment were Eastern Cooperative Oncology Group performance status of 0 or 1, measurable disease defined by Response Evaluation Criteria In Solid Tumors version 1.1 (RECIST v1.1), adequate haematological and end-organ function, and no autoimmune disease or active infections. Formalin-fixed paraffin-embedded tumour specimens with sufficient viable tumour content were needed from all patients before enrolment. Patients received treatment with intravenous atezolizumab (1200 mg, given every 3 weeks). PD-L1 expression on tumour-infiltrating immune cells (ICs) was assessed prospectively by immunohistochemistry. The co-primary endpoints were the independent review facility-assessed objective response rate according to RECIST v1.1 and the investigator-assessed objective response rate according to immune-modified RECIST, analysed by intention to treat. A hierarchical testing procedure was used to assess whether the objective response rate was significantly higher than the historical control rate of 10% at an α level of 0·05. This study is registered with ClinicalTrials.gov, number NCT02108652.

FINDINGS

Between May 13, 2014, and Nov 19, 2014, 486 patients were screened and 315 patients were enrolled into the study. Of these patients, 310 received atezolizumab treatment (five enrolled patients later did not meet eligibility criteria and were not dosed with study drug). The PD-L1 expression status on infiltrating immune cells (ICs) in the tumour microenvironment was defined by the percentage of PD-L1-positive immune cells: IC0 (<1%), IC1 (≥1% but <5%), and IC2/3 (≥5%). The primary analysis (data cutoff May 5, 2015) showed that compared with a historical control overall response rate of 10%, treatment with atezolizumab resulted in a significantly improved RECIST v1.1 objective response rate for each prespecified immune cell group (IC2/3: 27% [95% CI 19-37], p<0·0001; IC1/2/3: 18% [13-24], p=0·0004) and in all patients (15% [11-20], p=0·0058). With longer follow-up (data cutoff Sept 14, 2015), by independent review, objective response rates were 26% (95% CI 18-36) in the IC2/3 group, 18% (13-24) in the IC1/2/3 group, and 15% (11-19) overall in all 310 patients. With a median follow-up of 11·7 months (95% CI 11·4-12·2), ongoing responses were recorded in 38 (84%) of 45 responders. Exploratory analyses showed The Cancer Genome Atlas (TCGA) subtypes and mutation load to be independently predictive for response to atezolizumab. Grade 3-4 treatment-related adverse events, of which fatigue was the most common (five patients [2%]), occurred in 50 (16%) of 310 treated patients. Grade 3-4 immune-mediated adverse events occurred in 15 (5%) of 310 treated patients, with pneumonitis, increased aspartate aminotransferase, increased alanine aminotransferase, rash, and dyspnoea being the most common. No treatment-related deaths occurred during the study.

INTERPRETATION

Atezolizumab showed durable activity and good tolerability in this patient population. Increased levels of PD-L1 expression on immune cells were associated with increased response. This report is the first to show the association of TCGA subtypes with response to immune checkpoint inhibition and to show the importance of mutation load as a biomarker of response to this class of agents in advanced urothelial carcinoma.

FUNDING

F Hoffmann-La Roche Ltd.

Identification of a novel susceptibility locus at 13q34 and refinement of the 20p12.2 region as a multi-signal locus associated with bladder cancer risk in individuals of European ancestry

Candidate gene and genome-wide association studies (GWAS) have identified 15 independent genomic regions associated with bladder cancer risk. In search for additional susceptibility variants, we followed up on four promising single-nucleotide polymorphisms (SNPs) that had not achieved genome-wide significance in 6911 cases and 11 814 controls (rs6104690, rs4510656, rs5003154 and rs4907479, P < 1 × 10(-6)), using additional data from existing GWAS datasets and targeted genotyping for studies that did not have GWAS data. In a combined analysis, which included data on up to 15 058 cases and 286 270 controls, two SNPs achieved genome-wide statistical significance: rs6104690 in a gene desert at 20p12.2 (P = 2.19 × 10(-11)) and rs4907479 within the MCF2L gene at 13q34 (P = 3.3 × 10(-10)). Imputation and fine-mapping analyses were performed in these two regions for a subset of 5551 bladder cancer cases and 10 242 controls. Analyses at the 13q34 region suggest a single signal marked by rs4907479. In contrast, we detected two signals in the 20p12.2 region-the first signal is marked by rs6104690, and the second signal is marked by two moderately correlated SNPs (r(2) = 0.53), rs6108803 and the previously reported rs62185668. The second 20p12.2 signal is more strongly associated with the risk of muscle-invasive (T2-T4 stage) compared with non-muscle-invasive (Ta, T1 stage) bladder cancer (case-case P ≤ 0.02 for both rs62185668 and rs6108803). Functional analyses are needed to explore the biological mechanisms underlying these novel genetic associations with risk for bladder cancer.

Association Between Geographic Access to Cancer Care and Receipt of Radiation Therapy for Rectal Cancer

PURPOSE

Trimodality therapy (chemoradiation and surgery) is the standard of care for stage II/III rectal cancer but nearly one third of patients do not receive radiation therapy (RT). We examined the relationship between the density of radiation oncologists and the travel distance to receipt of RT.

METHODS AND MATERIALS

A retrospective study based on the National Cancer Data Base identified 26,845 patients aged 18 to 80 years with stage II/III rectal cancer diagnosed from 2007 to 2010. Radiation oncologists were identified through the Physician Compare dataset. Generalized estimating equations clustering by hospital service area was used to examine the association between geographic access and receipt of RT, controlling for patient sociodemographic and clinical characteristics.

RESULTS

Of the 26,845 patients, 70% received RT within 180 days of diagnosis or within 90 days of surgery. Compared with a travel distance of <12.5 miles, patients diagnosed at a reporting facility who traveled ≥50 miles had a decreased likelihood of receipt of RT (50-249 miles, adjusted odds ratio 0.75, P<.001; ≥250 miles, adjusted odds ratio 0.46; P=.002), all else being equal. The density level of radiation oncologists was not significantly associated with the receipt of RT. Patients who were female, nonwhite, and aged ≥50 years and had comorbidities were less likely to receive RT (P<.05). Patients who were uninsured but self-paid for their medical services, initially diagnosed elsewhere but treated at a reporting facility, and resided in Midwest had an increased the likelihood of receipt of RT (P<.05).

CONCLUSIONS

An increased travel burden was associated with a decreased likelihood of receiving RT for patients with stage II/III rectal cancer, all else being equal; however, radiation oncologist density was not. Further research of geographic access and establishing transportation assistance programs or lodging services for patients with an unmet need might help decrease geographic barriers and improve the quality of rectal cancer care.

Association Between Geographic Access to Cancer Care, Insurance, and Receipt of Chemotherapy: Geographic Distribution of Oncologists and Travel Distance

PURPOSE

Geographic access to care may be associated with receipt of chemotherapy but has not been fully examined. This study sought to evaluate the association between density of oncologists and travel distance and receipt of adjuvant chemotherapy for colon cancer within 90 days of colectomy.

PATIENTS AND METHODS

Patients in the National Cancer Data Base with stage III colon cancer, diagnosed between 2007 and 2010, and age 18 to 80 years were selected. Generalized estimating equation clustering by hospital service area was conducted to examine the association between geographic access and receipt of oncology services, controlling for patient sociodemographic and clinical characteristics.

RESULTS

Of 34,694 patients in the study cohort, 75.7% received adjuvant chemotherapy within 90 days of colectomy. Compared with travel distance less than 12.5 miles, patients who traveled 50 to 249 miles (odds ratio [OR], 0.87; P=.009) or ≥250 miles (OR, 0.36; P<.001) had decreased likelihood of receiving adjuvant chemotherapy. Density level of oncologists was not statistically associated with receipt of adjuvant chemotherapy (low v high density: OR, 0.98; P=.77). When stratifying analyses by insurance status, non-privately insured patients who resided in areas with low density of oncologists were less likely to receive adjuvant chemotherapy (OR, 0.85; P=.03).

CONCLUSION

Increased travel burden was associated with a decreased likelihood of receiving adjuvant chemotherapy, regardless of insurance status. Patients with nonprivate insurance who resided in low-density oncologist areas were less likely to receive adjuvant chemotherapy. If these findings are validated prospectively, interventions to decrease geographic barriers may improve the timeliness and quality of colon cancer treatment.

Abstract 1101: Functional genomics of HER2 and HER3 mutations and response to neratinib

Selective kinase inhibitors, such as erolotinib and lapatinib, and monoclonal antibodies, such as cetuximab, trastuzumab and pertuzumab, targeting EGFR and ERBB2 have elicited significant response rates in lung cancer patients harboring mutant EGFR alleles and breast cancer patients whose tumors harbor gene amplification of ERBB2. To date, only a small number of ERBB2 and ERBB3 mutations have been reported and biologically characterized. Moreover, the therapeutic impact of ERBB2 or ERBB3 mutant alleles and their value as an actionable target in patients has not been validated. While ERBB2 itself cannot bind ligand, it is a potent receptor that integrates growth signals via homo- or heterodimerization with other ERBB family members.

Genomic alterations increase ERBB2 kinase activity by constitutively activating the kinase domain, enabling ligand-independent receptor activation, by promoting enhanced dimerization or other mechanisms that have yet to be elucidated. Although ERBB3 has limited inherent kinase activity and cannot homodimerize, ligand stimulation promotes dimerization with active kinases like ERBB2 and EGFR that can phosphorylate ERBB2 which then promotes transformation.

Thus genomic alterations in ERBB3 may be a key means of promoting oncogenic signaling despite the protein lacking robust enzymatic activity. We performed an analysis of ∼100 large-scale next generation sequencing datasets newly generated by our group (bladder), our institution (MSKCC-IMPACT), or found in recently published repositories (The Cancer Genome Atlas (TCGA), Broad, Genentech, Sanger, etc) to characterize the distribution and spectrum of mutations in the ERBB2 and ERBB3 genes. Data generated suggests that ERBB2 and ERBB3 mutations are highly prevalent in bladder cancer (each ∼10%), and recurrent, but with less frequency (&lt;5%), in stomach, breast, colon and lung cancers. Hotspots include mutation of S310F and a cluster of residues in the kinase domain in ERBB2 and the V104M mutation in ERBB3. Preliminary analysis of ∼300 tumors demonstrated that ERBB2 and ERBB3 mutations present in a typically in a mutually exclusive pattern suggesting that these may be driver events with overlapping biologic effects. Generation and expression of several of these ERBB2 and ERBB3 mutants induced receptor activation, cell transformation and tumor growth in isogenic cell line and xenograft models. Treatment with the dual EGFR/HER2 inhibitor, neratinib, in isogenic cell lines abrogated colony formation in soft agar and receptor activation and downstream signaling. We hope to correlate the in vitro potency of specific ERBB2 and ERBB3 mutations with drug response in patients on ongoing or future clinical trials of targeted ERBB therapies and determine the whether lineage, subclonality and co-altered genes, if present, predict for drug resistance.

Citation Format: Aphrothiti J. Hanrahan, David M. Hyman, John Sfakianos, Alexis Jones, Ricardo Ramirez, Hannah Johnsen, Gopakumar Iyer, Hikmat A. Al-Ahmadie, Dean Bajorin, Bernard H. Bochner, Jonathan A. Coleman, Jonathan E. Rosenberg, Michael F. Berger, Sarat Chandarlapaty, Jose Baselga, David B. Solit. Functional genomics of HER2 and HER3 mutations and response to neratinib. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1101. doi:10.1158/1538-7445.AM2015-1101