Impact of sarcomatoid features on treatment outcomes in metastatic clear cell renal cell carcinoma treated with first-line immunotherapy combinations

687

Background: The presence of sarcomatoid features in clear cell renal cell carcinoma (cRCC) has historically been associated with poor response to tyrosine kinase inhibitor (TKI) monotherapy and poor overall survival; however, immunotherapy (IO) combination therapies have shown more promise in treating this variant. Front-line anti-PD-1 based IO combinations used in ccRCC include ipilimumab/nivolumab (IO/IO) and several combinations of a VEGFR-targeted TKI with a PD-1 inhibitor (TKI/IO). Here, we compare progression-free survival after therapeutic 1st-line (PFS) and 2nd-line (PFS-2) in patients who received IO/IO vs TKI/IO combinations as 1st line treatment for metastatic ccRCC, and test whether the treatment effects differ based on the presence or absence of sarcomatoid dedifferentiation. Methods: A retrospective analysis was performed on patients with ccRCC initiating 1st line combination IO at Memorial Sloan Kettering Cancer Center between 1/1/2014 and 12/30/2020. Patient cohorts were defined by 1st line treatment type: IO/IO or TKI/IO. PFS and PFS-2 were estimated using the Kaplan-Meier method. Restricted mean survival time (RMST) was calculated for PFS and PFS-2 in each 1st line treatment group and modelled using a generalized linear model adjusted for IMDC risk. To test for heterogeneity of treatment effect among subgroups, sarcomatoid features (presence/absence) is included in the models and an interaction test is performed. Results: Ninety patients (28 sarcomatoid) received 1st line IO/IO and 83 (17 sarcomatoid) received 1st line TKI/IO. Median PFS time is 6.8 months (95% CI: 4.5, 12.2) for IO/IO and 21 months (95% CI: 15, 25) for TKI/IO, p=0.009. After adjusting for IMDC risk, and after 48 months of follow-up, RMST for PFS was 10 months for IO/IO and 24 months for TKI/IO (p=0.02) and RMST for PFS-2 was 20 months for IO/IO and 23 months for TKI/IO (p=0.24). In the RMST model, the interaction between treatment group and presence or absence of sarcomatoid features is not significant for PFS (0.95) or PFS-2 (0.29). Conclusions: For ccRCC patients treated with 1st line IO/IO or TKI/IO, adjusted RMST for PFS was significantly longer for the TKI/IO group, but there was no statistically significant difference in adjusted RMST for PFS-2. Anti-PD-1-based therapy is an effective approach to treating ccRCC with sarcomatoid features. [Table: see text]

Molecular profile and clinical outcomes of renal cell carcinoma brain metastases treated with stereotactic radiosurgery

4526

Background: Molecular profiles of renal cell carcinoma (RCC) tumors are associated with systemic treatment (ST) responses and clinical outcomes. However, the molecular profiles of RCC brain metastases (BM) and their correlation with ST response and clinical outcomes are not well characterized. Effective management of BM with locoregional therapies including stereotactic radiosurgery (SRS) is critical as ST advances have improved overall survival (OS). Therefore, we sought to identify the clinical and genomic features of RCC BM in a large cohort of patients treated with SRS. Methods: We performed an institutional retrospective analysis of RCC BM patients treated with SRS and evaluated corresponding genomic next generation sequencing (NGS) data via a targeted sequencing panel (MSK-IMPACT). A comparison cohort of all institutional patients with available NGS data was utilized to investigate genes enriched in our BM cohort using Fisher exact testing. Kaplan Meier analyses were performed for OS and intracranial progression-free survival (iPFS). Clinical factors and genes mutated in ≥ 10% of samples were assessed per patient using Cox proportional hazards models, and per individual BMs using clustered competing risks regression with a competing risk of death. Results: From 2010-2021, 91 RCC BM patients underwent SRS for 212 BMs, including 86% clear cell and 14% non-clear cell RCC. NGS data was available for 76 patients (84%), including 18 resected BMs, 26 extra-cranial metastatic lesions (EM), and 32 primary kidney tumors (Table 1). Median follow-up was 3.2 years with median OS of 21 months (m) and median iPFS of 7.8m. Karnofsky performance status ≥80 and extracranial disease control were significantly associated with improved OS on multivariable analyses (MVA; p=0.049 and 0.01, respectively). No clinical variables were significantly associated with iPFS on MVA. At the BM level, SETD2 alterations approached significance for improved iPFS (HR=0.35; 95%CI 0.11, 1.05; p=0.06). Enrichment in SMARCA4 alterations was seen in the BM cohort as compared to primary kidney and EM samples from patients without BM (17% vs 1% vs 2%, p<0.05). Conclusions: To our knowledge, this is the largest study investigating mutational profiles of RCC BM. SMARCA4 alterations were enriched in BM samples and a trend towards improved iPFS was seen in SETD2 variant BMs, warranting further investigation.[Table: see text]

Long-term outcomes of adrenal insufficiency (AI) due to anti–PD(L)-1 immune checkpoint inhibitors (ICI) among patients with cancer

12092

Background: Endocrine immune-related adverse events (irAEs) to anti-PD-(L)1 ICI, including hypophysitis, autoimmune insulin-dependent diabetes mellites (ICI-DM), and primary adrenal insufficiency (AI), are rare but often associated with long term co-morbidities. AI from anti-PD-(L)1 ICI without CTLA-4 blockade is not well characterized in the literature. Long term outcomes for AI including need for replacement steroids and cortisol levels are unknown. Methods: We performed a single center retrospective analysis of patients treated with ICI including anti-programmed cell death protein-1 (Anti-PD-1: nivolumab or pembrolizumab), anti-programmed death-ligand-1 (anti-PD-L1: atezolizumab or cemiplimab) and diagnosed with ICI induced AI by a board-certified endocrinologist from 1/1/2011 to 12/31/2021. Patients treated with anti-CTLA-4 based therapy were not included. Patient baseline characteristics, presenting symptoms at the time of AI diagnosis, and treatment with corticosteroids were obtained by chart review. Baseline labs were collected at the time of AI and during routine patient follow-up. Descriptive statistics are reported for the cohort. Results: Twenty-nine patients were identified, 27 diagnosed with secondary and 2 diagnosed with primary AI. The median age was 63 (range 39-84), 18 (62%) males and 11 (38%) females, 14 (48%) receiving anti-PD(L)-1 monotherapy and 22 receiving anti-PD(L)-1 combination therapy either with chemotherapy (7, 24%), targeted therapy (6, 21%) or other/investigational therapy (2, 7%). The common tumor types were 6 renal cell carcinoma, 4 urothelial carcinoma, 4 melanoma, 15 others. The common presenting symptoms were 26 (90%) with fatigue,16 (55%) weakness, 11 (38%) nausea/vomiting, 4 (14%) headaches and 2 (7%) arthralgias. The common concomitant irAEs were 16 (55%) hypothyroidism, 8 (28%) acute kidney injury, 7 (24%) colitis, 6 (21%) joint pain, 3 (10%) pneumonitis & dermatitis. Eleven (38%) patients were treated with high dose steroids. Median follow-up time for survivors in the cohort was 24 months (range 7-68). Median cortisol level at time of AI diagnosis was 1.1 (IQR 0.9, 2.7; n = 27) and 1.8 (IQR 0.6, 6.4; n = 10) at last follow-up (median lab follow-up 39 months, range 29-58); 7 of 10 patients with available data had cortisol < 5.0 at last follow-up. For secondary AI patients, median ACTH at time of diagnosis was 2.3 (IQR 2.0, 5.0; n = 21) and 2.0 (IQR 2.0, 7.2; n = 7) at last follow-up. Twenty-two of 23 patients with available data continued replacement steroids at last follow-up. Conclusions: AI associated with anti-PD(L)-1 ICI is primarily secondary. Cortisol and ACTH levels remain low even during long-term follow-up. Most patients need long-term replacement steroids. Systemic and comprehensive follow-up for patients who develop AI due to anti-PD(L)-1 ICI is needed to confirm these findings.

Progression-free survival after second line of therapy (PFS-2) for metastatic clear cell renal cell carcinoma (ccRCC) in patients treated with first-line immunotherapy combinations

4536

Background: Front-line therapy with immunotherapy combinations is standard of care for metastatic ccRCC, with ipilimumab/nivolumab (IO/IO) and several combinations of a VEGFR-targeted tyrosine kinase inhibitor with a PD-1 inhibitor (TKI/IO) showing superior efficacy to TKI monotherapy. PFS-2 evaluates the ability to be salvaged by 2nd line therapy and is a surrogate for overall survival (OS). PFS-2 was compared in patients receiving 1st line IO/IO vs TKI/IO for metastatic ccRCC. Methods: A retrospective analysis was performed on patients with ccRCC treated at Memorial Sloan Kettering Cancer Center between 1/1/2014 and 12/30/2020, in cohorts defined by 1st line: IO/IO or TKI/IO. PFS-2 is defined as time from start of 1st line to progression on next therapy, or death. Patients without a PFS-2 event were censored at a prespecified cutoff date. Objective response rate to 1st (ORR1st) and 2nd (ORR2nd) line are compared with the Fisher’s exact test. OS, PFS-2, and time on therapy are estimated with the Kaplan-Meier method and compared with the log-rank test. Results: One hundred seventy-three patients received 1st line IO/IO (N = 90) or 1st line TKI/IO (N = 83); respectively, 52 and 40 patients had a PFS-2 event. 1st line TKI/IO regimens included: 34% axitinib/pembrolizumab, 29% lenvatinib/pembrolizumab, 25% axitinib/avelumab, 11% other. More IO/IO patients had brain metastases and intermediate/poor MSKCC risk category (respectively p = 0.007, p < 0.001). ORR1st and median months on 1st line were higher with TKI/IO vs IO/IO (65% vs 39%, p < 0.001; 16.1 vs 5.1, p < 0.001). ORR2nd was higher with IO/IO vs TKI/IO (47% vs 13%, p < 0.001), and median months on 2nd line was not significantly different (7.7 vs 7.1, p = 0.30). Median PFS-2 for TKI/IO was 44 months (95% CI: 27, 53) vs 23 months (95% CI: 16, 47) for IO/IO, p = 0.13. For TKI/IO and IO/IO groups, respective PFS-2 at 12 months was 86% (95% CI 77, 92) and 74% (95% CI 63, 82); PFS-2 at 36 months was 51% (95% CI 39, 63) and 42% (95% CI 30, 53). OS was not significantly different (p = 0.32; 3 year OS: IO/IO 60%, 95% CI 47, 71; TKI/IO 62%, 95% CI 49, 73). (Table) Conclusions: In patients receiving 1st line IO/IO or TKI/IO, ORR2nd was higher with IO/IO and median PFS-2 was numerically higher with TKI/IO, but no statistically significant difference in PFS-2 or OS was seen. These findings suggest that IO/IO and TKI/O are both acceptable 1st line treatment strategies in ccRCC. [Table: see text]

The frequency of second primary malignancies and colonic polyps in Lynch syndrome with MSI tumors following immune checkpoint blockade

10505

Background: Lynch syndrome (LS) is caused by germline mutations in DNA mismatch repair genes and is characterized by microsatellite instability (MSI) status of associated tumors. MSI sensitizes tumors to immune checkpoint inhibition (ICI). The incidence of second primary malignancies and colonic polyps in LS patients with MSI tumors following ICI has not been evaluated. Methods: The Memorial Sloan Kettering LS database was queried for all patients with cancer who received ≥1 cycle of ICI using an IRB approved protocol. LS was confirmed by presence of a germline pathogenic/likely pathogenic alteration in a DNA mismatch repair gene ( MLH1, MSH2, MSH6, PMS2, EPCAM). Tumor and matched normal DNA sequencing was performed via MSK-IMPACT, an IRB approved protocol (NCT01775072). MSI status was assessed using MSIsensor. Results: At our center, 131 patients with LS received ICI mostly (73.3%) in the context of metastatic cancer. While 108 patients received ICI for an MSI tumor, 23 LS patients received ICI for a MSS (Microsatellite Stable) tumor (4 hepatobiliary, 3 colorectal, 3 CNS, 2 endometrial, 2 gastroesophageal, 2 renal, 2 sarcoma, 5 other). Five patients (3.8%) developed ≥1 second primary malignancy while on or following ICI comprised of an MSI small bowel adenocarcinoma, MSI upper tract urothelial cancer, 2 MSS prostate cancers, MSS HCC and MSI sebaceous neoplasm; 1 patient developed both MSS prostate cancer and MSI urothelial cancer on ICI. All five patients’ primary malignancy was MSI. Only a minority of patients underwent surveillance colonoscopies post completion of ICI (31.3%, (41/131)). Of these 41, nine (22%, (9/41)) were identified to have polyps including 8 tubular adenomas and 1 tubulo-villous adenoma. Median time to development of a polyp was 22 months (95% CI 16.82-27.18) from last colonoscopy and 13 months (95% CI 4-25 months) from last ICI. Notably amongst the 23 LS patients whose tumors were MSS, 14 had progression on ICI. Conclusions: Herein, we demonstrate that in LS-patients in receipt of ICI for cancer treatment, the risk of a second primary cancer and polyps remain high following treatment with ICI. Biological mechanisms underlying immune escape warrant further investigation. Surveillance strategies should be continued for LS patients post ICI.

Phase II Trial of Cabozantinib Plus Nivolumab in Patients With Non-Clear-Cell Renal Cell Carcinoma and Genomic Correlates

PURPOSE

To assess the efficacy and safety of cabozantinib plus nivolumab in a phase II trial in patients with non-clear-cell renal cell carcinoma (RCC).

PATIENTS AND METHODS

Patients had advanced non-clear-cell renal carcinoma who underwent 0-1 prior systemic therapies excluding prior immune checkpoint inhibitors. Patients received cabozantinib 40 mg once daily plus nivolumab 240 mg once every 2 weeks or 480 mg once every 4 weeks. Cohort 1 enrolled patients with papillary, unclassified, or translocation-associated RCC; cohort 2 enrolled patients with chromophobe RCC. The primary end point was objective response rate (ORR) by RECIST 1.1; secondary end points included progression-free survival, overall survival, and safety. Next-generation sequencing results were correlated with response.

RESULTS

A total of 47 patients were treated with a median follow-up of 13.1 months. Objective response rate for cohort 1 (n = 40) was 47.5% (95% CI, 31.5 to 63.9), with median progression-free survival of 12.5 months (95% CI, 6.3 to 16.4) and median overall survival of 28 months (95% CI, 16.3 to not evaluable). In cohort 2 (n = 7), no responses were observed; one patient had stable disease > 1 year. Grade 3/4 treatment-related adverse events were observed in 32% treated patients. Cabozantinib and nivolumab were discontinued because of toxicity in 13% and 17% of patients, respectively. Common mutations included NF2 and FH in cohort 1 and TP53 and PTEN in cohort 2. Objective responses were seen in 10/12 patients with either NF2 or FH mutations.

CONCLUSION

Cabozantinib plus nivolumab showed promising efficacy in most non-clear-cell RCC variants tested in this trial, particularly those with prominent papillary features, whereas treatment effects were limited in chromophobe RCC. Genomic findings in non-clear-cell RCC variants warrant further study as predictors of response.

A phase II study of talazoparib and avelumab in VHL deficient clear cell renal cell carcinoma

347

Background: VHL inactivation may lead to impairments in the DNA damage response pathway and increased replication stress, which consequently can increase the genomic instability of clear cell renal cell carcinoma (RCC). Other molecularly driven RCC subtypes including FH and SDH deficient RCC show impaired DNA repair through oncometabolite accumulation. Synthetic lethality with PARP inhibitors (PARPi) has been suggested in preclinical models, and PARPi may potentiate the effects of immune checkpoint blockade (ICB) therapy. Methods: We conducted a single center, investigator-initiated phase II trial to evaluate combined PARPi + PD-L1 inhibition in two genomically selected advanced RCC cohorts: 1) VHL altered RCC; 2) FH, SDH-RCC and renal medullary carcinoma. For Cohort 1, patients had to have previously been treated with VEGFR TKI and ICB therapy with maximum 3 prior lines of therapy. Patients received talazoparib 1mg daily plus avelumab 800mg IV every 14 days. The primary endpoint was objective response rate (ORR) by iRECIST, and secondary endpoints included progression-free survival (PFS), safety and tolerability. Results from Cohort 1 are reported here. Results: From 2019-2021, 10 advanced RCC patients were enrolled per the first stage of a Simon 2-stage design for cohort 1. The median age was 63 years (R: 42-71), and median number of prior therapies was 2 (R: 1-3). All patients had VHL loss detected by tissue NGS sequencing via MSK-IMPACT, and 3/10 (30%) of patients had co-occurring somatic or germline alterations in DDR specific genes. No objective tumor responses were seen, and the disease control rate was 60% (6/10) with those patients achieving stable disease as best response. All patients experienced disease progression and the median PFS was 3.6 months (95% CI 1.4-4.9). Adverse events were in keeping with reported toxicities for individual agents without emerging safety signals. Conclusions: This is the first clinical study of combination PARPi and ICB therapy in advanced clear cell RCC. In our cohort of VHL deficient TKI/ICB refractory RCC, the study did not meet its pre-defined efficacy threshold to continue enrollment, and our results do not support further study of this regimen in this population. Exploratory efforts to evaluate this treatment approach in other biomarker selected populations of RCC, including cohort 2 of this study, are ongoing. Clinical trial information: NCT04068831.

Defining hereditary upper tract urothelial carcinoma: Implications for genetic testing and clinical management

523

Background: Despite being a rare cancer, upper tract urothelial carcinoma (UTUC) is the third most common core cancer associated with Lynch syndrome (LS) after colorectal and endometrial cancers. Yet, there is no established guideline to identify patients with UTUC who are at risk of carrying germline mutations in LS-associated genes. The objective of this study is to define selection criteria for patients with UTUC for LS screening. Methods: We retrospectively identified patients with UTUC who underwent germline sequencing of ≥77 cancer susceptibility genes using next generation sequencing (NGS) as part of a prospective matched tumor-normal genomic profiling initiative from 04/2015 to 04/2021. Mismatch repair protein status was evaluated by immunohistochemical (IHC) staining for MMR genes MSH2, MSH6, MLH1, and PMS2. Microsatellite instability (MSI) status was determined using NGS. Diagnostic performance of clinical and tumor-based screening criteria was assessed by the presence of germline pathogenic/likely pathogenic variants (PGVs) in MMR genes. Results: A total of 232 patients with UTUC underwent germline testing; median age of diagnosis was 67 years (interquartile range 59 – 73). Of these patients, 70% were male, 43% had UTUC diagnosed before the age of 65, 85% had high grade UTUC,12% had bilateral UTUC, 11% had metastasis at diagnosis, 10% and 31% had personal and family history of LS-associated cancers, respectively. PGVs in moderate or high-penetrance genes were identified in 31 (13%) patients including 6 (3%) in BRCA1/ 2 and 21 (9%) in MMR genes (13 MSH2, 4 MSH6, 4 MLH1). A total of 10/21 (48%) patients with MMR PGVs developed UTUC as their first cancer diagnosis. Of patients with MMR PVGs, 15/16 (94%) had MMR-deficient tumors and 12/18 (67%) had MSI-high tumors. Personal and family history of LS core cancers (p < 0.001), age of diagnosis < 65 (p = 0.008), MSI-high (p < 0.001), and MMR-deficiency (p < 0.001) were associated with MMR carrier status. Female gender (p = 0.7), HG UTUC (p = 0.5), and bilateral UTUC (p = 0.7) were not associated with MMR PGVs. Current NCCN genetic referral criteria for Lynch syndrome has high specificity in identifying patients with LS (100%) but missed 11/21 (52%) patients with UTUC and MMR PGVs. Conclusions: Current genetic referral guidelines for Lynch syndrome may miss a significant portion of patients with LS-associated UTUC. UTUC tumor should be investigated for MMR protein and MSI status with IHC or next generation sequencing methods to augment LS-screening of patients with UTUC and inform systemic treatment selection.

Nivolumab plus cabozantinib in patients with non-clear cell renal cell carcinoma: Results of a phase 2 trial

4509

Background: Cabozantinib plus nivolumab (CaboNivo) improved objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) over sunitinib in a phase 3 trial for metastatic clear cell renal cell carcinoma (RCC). (Choueiri, abstract 6960, ESMO 2020) We report the results of a phase 2 trial of CaboNivo in patients (pts) with non-clear cell RCC. Methods: Pts had advanced non-clear cell RCC, 0 or 1 prior systemic therapies excluding prior immune checkpoint inhibitors, and measurable disease by RECIST. Cabo 40 mg/day plus Nivo 240 mg every 2 weeks or 480 mg every 4 weeks was given across two cohorts. Cohort 1: papillary, unclassified, or translocation associated RCC; Cohort 2: chromophobe RCC. The primary endpoint was ORR by RECIST; secondary endpoints included PFS, OS, and safety. Cohort 1 was a single stage design that met its primary endpoint and was expanded to produce more precise estimates of ORR. Cohort 2 was a Simon two-stage design that closed early for lack of efficacy. Correlative analyses by next generation sequencing were performed and to be presented. Results: A total of 40 pts were treated in Cohort 1, and 7 pts were treated in Cohort 2 (data cutoff: Jan 20, 2021). Median follow up time was 13.1 months (range 2.2 – 28.6). In Cohort 1, 26 (65%) pts were previously untreated, and 14 (35%) pts had 1 prior line: 10 (25%) received prior VEGF-targeted therapy and 8 (20%) received prior mTOR-targeted therapy. ORR for Cohort 1 was 48% (95% CI 31.5–63.9; Table). Median PFS was 12.5 months (95% CI 6.3–16.4) and median OS was 28 months (95% CI 16.3–NE). No responses were seen among 7 patients in Cohort 2 with chromophobe histology (Table). Grade 3/4 treatment emergent adverse events were consistent with that reported in the phase 3 trial; Grade 3/4 AST and ALT were 9% and 15%, respectively. Cabozantinib and nivolumab were discontinued due to toxicity in 17% and 19% of pts, respectively. Conclusions: CaboNivo had an acceptable safety profile and showed promising efficacy in metastatic non-clear cell RCC pts with papillary, unclassified, or translocation associated histologies whereas activity in patients with chromophobe RCC was limited. Clinical trial information: NCT03635892. [Table: see text]

Early age of onset and broad cancer spectrum persist in MSH6 and PMS2-associated Lynch syndrome

10516

Background: Recently updated NCCN guidelines for management of germline MSH6 and PMS2 pathogenic/likely pathogenic (P/LP) variant carriers suggest a more modest phenotype with later onset colorectal cancer (CRC) and limited extra-colonic cancers compared to other Lynch Syndrome (LS) genes. However, data are limited, and a comprehensive understanding of the risk spectrum and age of cancer onset is critical for cancer screening and risk-reduction. We sought to characterize MSH6 and PMS2-associated cancers and age of diagnosis in those with mismatch repair deficient (MMRD)/ microsatellite instability-high (MSI-H) tumors, a hallmark of LS pan-cancer. Methods: Pts consented to IRB-approved protocols of tumor/germline sequencing or to a prospective registry of LS pts at a single institution from 2/2005-01/2021 were reviewed to identify those with germline heterozygous MSH6/ PMS2 P/LP variants; pts with constitutional MMRD (CMMRD) were excluded. In cancer-affected pts, tumors were evaluated for MSI and/or MMR protein expression via immunohistochemistry. Tumor types were tabulated, and clinical variables were correlated with MMR/MSI status using non-parametric tests. Results: We identified 243 pts (159 female, 94 male) with P/LP germline MSH6/PMS2 variants, and 186 (77%) pts had a confirmed cancer [ MSH6 111/148 (75%); PMS2 75/95 (79%)]. Overall, 51 (21%) pts had multiple primary cancers, 35 (24%) in MSH6 and 16 (17%) in PMS2 (p = 0.20), resulting in 261 total tumors, 160 in MSH6 and 101 in PMS2. Of the 191 tumors with molecular assessment, 118 (62%) were MMRD/MSI-H, including CRC (n = 54), endometrial (EC, n = 34), small bowel (SBA, n = 6), ovarian (OC, n = 5), urothelial (n = 5), pancreato-biliary (n = 4), gastroesophageal (n = 3), non-melanoma skin (n = 3), prostate (n = 2), breast (n = 1), and brain (n = 1). While CRC and EC were more likely to be MMRD/MSI-H (79% each) compared to other cancers (37%) (p < 0.001 overall, p = 0.001 for MSH6, and p < 0.001 for PMS2), 25% of all MMRD/MSI-H tumors in both genes were comprised of non-CRC/EC cancers. Notably, there were 6 SBAs (5 in PMS2, 1 in MSH6), and all were MMRD/MSI-H. There were 17 OCs (12 in PMS2, 5 in MSH6), and of the 12 that underwent molecular assessment, 5 (41.7%) were MMRD/MSI-H (3 PMS2, 2 MSH6). Among MMRD/MSI-H CRC and EC, median age of diagnosis was 51.5 (range 27-80) and 55 (range 39-74) respectively, with 9/54 (17%) of CRC (4 in MSH6, 5 in PMS2) diagnosed < age 35, the suggested upper threshold for initiation of colonoscopy per NCCN. Conclusions: Despite being lower penetrance LS-associated genes, pts with MSH6/PMS2 P/LP variants remain at risk for a broad-spectrum of cancers and very early-onset CRC, with 17% of MMRD/MSI-H CRC presenting prior to upper threshold of initiation of colonoscopic screening per NCCN.

Characterization of findings on prostate cancer tumor sequencing that should prompt consideration for germline testing

5022

Background: Tumor sequencing is increasingly used for therapeutic selection in men with advanced prostate cancer (PC). If tumor-only sequencing is performed without matched germline, identified mutations could be of somatic or germline origin. Germline mutations could confer additional risk for other cancers to the patient and at-risk family members. The objective of this study is to determine the overall and gene-specific probability of pathogenic/likely pathogenic germline mutations based on tumor-only sequencing. Methods: We investigated mutations found in a cohort of men with PC who underwent targeted next generation sequencing of PC tumor and matched peripheral blood using the MSK-IMPACT assay between 01/2015 and 01/2020. A germline probability for each gene was determined by dividing the number of germline mutations by the total number of somatic and germline mutations. Cancer susceptibility genes commonly sequenced on tumor-based tests for PC were assessed, including ATM, BRCA1/ 2, BRIP1, CHEK2, HOXB13, MLH1, MSH2, MSH6, NBN, PALB2, PMS2 (henceforth referred to as PC genes). Results: A total of 1883 men with PC were included, with median age of diagnosis of 62.0 ± 8.8 years. 84% had high risk PC, 52% had metastasis, 38% had family history of PC. A total of 364 (19%) men had at least one mutation (either somatic or germline) in PC genes. Overall, 189 (10%) men had at least one germline mutation that would not have been reported as germline without matched normal. The average germline probability of PC genes was 40% (range: 0% in MLH1 to 83% in CHEK2). The number of total mutations, germline mutations, and germline probability of genes found in > 0.5% of the study cohort are summarized in Table. All these genes are moderate/high penetrance autosomal dominant genes with established guidelines for cascade testing, enhanced cancer screening, or potential risk-reducing surgery. Conclusions: In this study, an average of 40% of mutations found in cancer susceptibility genes on PC tumor sequencing were germline mutations. Men undergoing tumor-only sequencing should be counseled on the possibility of uncovering a germline mutation. In addition to BRCA1/ 2, mutations in certain genes, such as CHEK2 and PALB2, have a high probability of being germline and should prompt referral for genetic counseling and germline testing.[Table: see text]

Disparities in pan-cancer patients undergoing germline cancer risk assessment by self-reported race/ethnicity and ancestry

10508

Background: Disparities in access to germline testing for cancer patients (pts) have been demonstrated; however, disparities in post-testing care are unknown. We sought to evaluate germline findings and subsequent genetic counseling/care in cancer pts undergoing tumor-germline sequencing to explore differences by self-reported ancestry. Methods: Pan-cancer pts were prospectively consented to tumor-normal sequencing via a custom NGS panel (MSK-IMPACT) from 1/2015-12/2019 inclusive of germline analysis up to 88 genes. Germline analysis was performed as a research non-billable test in 97.5% of cases. Referral to clinical genetics service (CGS) was recommended for all pts with a new positive (likely pathogenic/pathogenic) germline variant (PV). Ancestry was defined using self-reported Federal definitions of race/ethnicity and designations of Ashkenazi Jewish (AJ) ancestry. Pts were categorized into mutually exclusive groups: AJ, White, Non-White (Asian, Black/African American, Hispanic, Other), and unknown. All pts self-identifying as Hispanic were classified as such, regardless of race. Abstracted data on germline findings and downstream CGS follow-up were compared across groups using non-parametric statistical tests. Results: Among the 15,775 pts in this cohort (59.6% White, 15.7% AJ, 20.5% Non-White [6.9% Asian, 6.8% Black, 6.7% Hispanic, 0.1% Other], and 4.2% unknown), 2663 (17%) had a PV. AJ pts had the highest rates of PV (n = 683, 27.6%), and Non-White pts had a lower proportion of PV (n = 433, 13.6%) compared to Whites (n = 1451, 15.5%), p < 0.01, with differences mostly due to increased prevalence of moderate/low penetrance variants in White and AJ pts . These findings were consistent across multiple tumor types. Prior knowledge of the PV (424/2663, 16%) was more common in Non-White (19.9%) and AJ (19.2%) than White pts (13.4%), p < 0.01. Among 2239 pts with new PV, all were referred to CGS, and 1652 (73.8%) pts were seen. Non-White pts had lower rates of completing visits (67.7%) than White (73.7%) and AJ pts (78.8%), p < 0.01, with the lowest rates occurring in Black (63%) and Hispanic (68.1%) pts. All pts without a visit (n = 587) received a close out letter including 139 pts (6.2% of pts with new PV) who had no documentation of receipt of results in the medical record. Higher rates of non-disclosure were observed in Non-White (6.7%) compared to White (5.4%) and AJ (3.4%) pts with new PV, p = 0.032; non-disclosure did not vary by gene penetrance. There was a non-significant trend towards lower rates of cascade testing at CGS in Asian and Black pts with ongoing analysis. Conclusions: Even when traditional barriers to genetic testing were minimized, Non-White pts were less likely to receive recommended cancer genetics follow-up for subsequent cancer risk counseling, with potential implications for oncological care, cancer risk reduction, and at-risk family members.

Germline alterations in cancer susceptibility genes in women with high-risk bladder cancer: Implications for germline testing and clinical management

418

Background: Gender differences exist in bladder cancer incidence, stage at diagnosis, and outcomes. Women have lower incidence of bladder cancer but are diagnosed with more advanced disease at presentation. They also have less favorable outcomes even after adjusting for tumor stage and treatment modality. The biologic mechanisms underlying gender disparities in bladder cancer remain unknown. Methods: We leveraged a prospective matched tumor-normal genomic profiling initiative to determine the prevalence and spectrum of pathogenic/likely pathogenic (P/LP) germline variants in women with bladder cancer. Germline DNA was tested for mutations in ≥77 cancer susceptibility genes using next-generation sequencing in 686 patients with bladder cancer. Mutation frequency and clinical characteristics were assessed by gender. Results: A total of 184 (27%) women and 502 (73%) men with bladder cancer underwent germline testing; median age of diagnosis was 66 ± 11.3 and 65 ± 11.3 years, respectively. Twenty-two women (12%) had bladder cancer diagnosis at age ≤ 50 years. Both groups had similar rate of tobacco exposure (57% vs 63%, p = 0.1), family history of bladder cancer (10% vs 10%, p = 0.5), and disease stage at diagnosis (non-muscle invasive bladder cancer [NMIBC] 54% vs 54%, MIBC 38% vs 39%, and metastatic disease 8% vs 6%, p = 0.7). Women had more non-urothelial carcinoma histology than men (adenocarcinoma 5% vs. 1%; squamous cell carcinoma 1% vs 0.2%, p = 0.001). More P/LP germline variants were found in women than men (38 [21%] vs. 70 [14%], p = 0.04). Twenty-eight women (15%) had P/LP variants in DNA-damage repair (DDR) genes; 23 (13%) carried moderate/high penetrance germline mutations, the most common were BRCA1/ 2, CHEK2, NBN, ATM, and MITF. Current clinical guideline for referral for genetic testing failed to identify 12 (52%) women with moderate/high penetrance germline mutations. Nine women (5%) carried germline mutations associated with increased risk of ovarian/endometrial cancers ( BRCA1/ 2 [5], ATM [2], MLH1 [1], TP53 [1]). Conclusions: Deleterious germline alterations are commonly present in women with high-risk bladder cancer. The presence of germline variants in some genes, such as BRCA1/2, can guide cancer screening and risk-reducing surgeries for patients and their families. Women with high-risk bladder cancer should be evaluated for suitability of germline testing, especially those who desire preservation of uterus and ovaries at the time of radical cystectomy, to rule out the presence of P/LP variants that increase risk of future gynecologic malignancies.

Evaluation of germline genetic testing criteria in early-onset kidney cancer

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Background: An estimated 5% of kidney cancers are associated with hereditary RCC syndromes. Current germline genetic testing guidelines for patients with kidney cancer were developed to identify carriers of known RCC-associated genes and have evolved in the panel-testing era. We evaluated the utility of the recent National Comprehensive Cancer Network (NCCN) recommendation of testing all patients with early-onset RCC (defined as age of diagnosis ≤ 46 years) for germline variants in genes implicated in hereditary RCC syndromes. Methods: We retrospectively identified patients with RCC diagnosed at age ≤ 46 years who underwent targeted germline testing at our institution through referral to clinical genetics service (n = 68, 29%) or through broad germline testing of ≥77 cancer susceptibility genes using next generation sequencing as part of a prospective matched tumor-normal genomic profiling initiative (n = 165, 71%). Diagnostic performance of referral criteria was assessed by the presence of pathogenic/likely pathogenic (P/LP) germline variants in RCC-associated genes and incidental cancer susceptibility genes. Results: Of 233 patients, 61% were male, 74% were Caucasian, 15% had family history of RCC, 15% had RCC-syndromic features, including 9% with multifocal renal tumors. Most patients (54%) had clear cell RCC (ccRCC). P/LP germline variants were identified in 42 (18%) patients but only 21 (9%) had mutations in RCC genes (12 FH, 4 VHL, 2 SDHB, 1 each in BAP1, TSC1, and FLCN). All 21 early-onset patients with germline variants in an RCC-associated gene also had one of the following risk factors: non-ccRCC histology, family history, or syndromic features. In 91 patients (39%) with a non-RCC germline variants or no alteration, none of these three risk factors were found. Of 21 patients with non-RCC P/LP germline variants, 9 had mutations in moderate/high penetrance genes ( BRCA1 [2], ATM [2], CHEK2 [1], TP53 [2] , PALB2 [1], and RET [1]); 8/9 (89%) met standard criteria for testing for those genes independent of early-onset RCC diagnosis. Conclusions: Patients with early-onset clear cell RCC and no suspicious personal or family history are unlikely to have an RCC-associated germline mutation. RCC-gene panel testing has highest utility in early-onset patients with either non-ccRCC histology, family history of RCC, or RCC-associated syndromic features. Given the high frequency of non-RCC P/LP variants, early-onset RCC patients should be counseled regarding broader testing beyond RCC-associated genes.

A pilot study of preoperative nivolumab in high-risk nonmetastatic renal cell carcinoma

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Background: Immunotherapy improves survival in patients with advanced renal cell carcinoma (RCC), but has no established role for perioperative use in patients with localized RCC. Neoadjuvant immunotherapy is a promising strategy in several cancers, and may leverage the primary tumor as antigen source. Methods: We conducted a single institution pilot study of neoadjuvant nivolumab in patients with RCC undergoing nephrectomy with curative intent. Patients were eligible if their risk of metastatic recurrence within the first 12 years was >20% by an established nomogram. After confirmatory biopsy and renal MRI, patients were treated with standard dose nivolumab every 2 weeks for 4 treatments, with a follow-up renal MRI prior to nephrectomy. The primary end points of the study were safety and feasibility defined as being able to complete 3/4 treatments without surgical delay. We evaluated adverse events by CTCAE, surgical safety by Clavien-Dindo classification, and tumor radiographic response by RECIST 1.1. Results: Eighteen (11 men, 7 women; median age 60) were enrolled. All patients had clear cell RCC, median tumor size at baseline was 8.8cm (range 6.4-14.2cm). Median predicted 12-year probability of recurrence was 45% (range 25-71%). All received at least 1 dose of nivolumab; 16/18 patients completed all 4 doses. 17/18 (94%) patients completed at least 3 doses. No patient had notable delay in the timing of their nephrectomy. 4 patients had surgical complications per Clavien-Dindo classification, including 2 with grade 3a chylous ascites after lymphadenectomy. Two patients had nivolumab discontinued for immune-related adverse events, including grade 3 transaminitis and grade 2 arthralgias; a third patient developed grade 4 colitis 4 months after completing nivolumab. All patients had stable disease as the best response prior to surgery. Recurrence-free survival at 2 years was 0.74 (95%CI 0.45-0.90). We analyzed an additional 21 patients with metastatic RCC (20 ccRCC, 1 epithelioid AML) who subsequently had nephrectomy after standard immunotherapy. 15 patients had received ipilimumab+nivolumab, 6 received single-agent PD-1 or PD-L1 inhibitors. 3 (14%) patients achieved a near or complete pathologic response, including a patient with epithelioid AML. Analysis of radiologic and pathologic biomarkers of response are ongoing and will be presented at conference. Conclusions: In this pilot study, there were no new safety signals or delays in surgery with preoperative nivolumab. Neoadjuvant immunotherapy shows preliminary evidence of safety, feasibility and efficacy; biomarker studies may help identify individuals who may have a higher likelihood of response. Clinical trial information: NCT02595918 .

Prevalence and clinical characterization of MMR-D/MSI extra-colonic cancers among germline PMS2 mutation carriers

1527

Background: PMS2-associated Lynch syndrome (LS) may have a more modest phenotype than that associated with other mismatch repair (MMR) genes ( MLH1, MSH2, MSH6, EPCAM). Recent studies suggest limited extra-colonic cancers, and modified risk-reducing measures can be provided. Understanding the spectrum of risk is of critical importance as some LS-associated cancers do not have effective screening, requiring risk-reducing surgery (endometrial, ovarian). As MMR-deficiency (MMRD)/ microsatellite instability (MSI) is associated with LS pan-cancer, we sought to characterize PMS2-associated malignancies according to MMR/MSI status. Methods: Review of cancer patients (pts) consented to an IRB-approved protocol of tumor/germline next-generation sequencing (NGS) identified 43 germline heterozygous PMS2 mutation carriers. Tumors were evaluated for MSI via MSIsensor and/or corresponding MMR protein expression via immunohistochemical staining (IHC). Clinical variables were correlated with MMR/MSI status, comparing via Chi-square or standard T-test. Results: There were > 10 tumor types; 69.8% (30/43) were extra-colonic cancers (endometrial (n = 4), ovarian (n = 6), small bowel (n = 3), urothelial (n = 2), pancreas (n = 3), prostate (n = 3), breast (n = 3), brain (n = 3), biliary (n = 1), spindle cell sarcoma (n = 1), and hepatoblastoma (n = 1)). 46.5% (20/43) of tumors were MMRD/MSI. 61.5% (8/13) of colorectal cancers (CRC) were MMRD/MSI, compared to 40% (12/30) of extra-colonic tumors. All endometrial and small bowel cancers were MMRD/MSI. Of 6 ovarian cancers, 3 were clear-cell, 1 endometrioid, and 2 high-grade serous (HGS). The only MMRD/MSI ovary tumor was HGS. 73.9% (17/23) of pts with MMRP/MSS tumors had recurrent/metastatic disease vs 30% (6/20) of pts with MMRD/MSI tumors ( p= 0.004). Mean age at diagnosis did not differ significantly between MMRP/MSS and MMRD/MSI groups (49 vs. 57, respectively, p= 0.146). 11.6% (5/43) of pts had a prior cancer, with only one patient having prior CRC. Pts with extra-colonic tumors were less likely to meet clinical pt and family history LS testing criteria than those with CRC (63.3% (19/30) vs. 7.7% (1/13); p< 0.001). Conclusions: While PMS2-related LS may have a more modest clinical phenotype, in this single-institution study, 60% (12/20) of patients with MMRD/MSI tumors presented with extra-colonic cancers. We caution counseling pts with PMS2-associated LS about reduced extra-colonic risk until more complete information about penetrance, spectrum, and age distribution of cancer is available.

Prospective agnostic germline testing in pediatric cancer patients

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Background: We report our large cohort of pediatric cancer patients undergoing prospective agnostic germline sequencing. Our dataset is a significant addition to the 1,573 children reported to date who have undergone agnostic germline sequencing in previous large sequencing studies, each with ascertainment bias. Methods: 676 patients with pediatric solid tumors underwent matched tumor-normal targeted DNA sequencing from July 2015 to February 2020. At least 76 genes associated with cancer predisposition were analyzed in the germline, and variants were classified per American College of Medical Genetics guidelines. Pathogenic and likely pathogenic (P/LP) variants were reported to patients/families, who were offered genetic counseling and cascade testing with screening recommendations and referral to a surveillance clinic as appropriate. Results: One or more P/LP variants were found in 17% (115/676) of individuals when including low, moderate and high penetrance mutations in recessive and dominant genes, or 12% (81/676) when including moderate and high penetrance mutations in dominant genes. P/LP variants were detected in 40% (21/53) of patients with retinoblastomas, 8% (13/161) with neuroblastomas/ganglioneuroblastomas, 13% (14/112) with brain/spinal tumors, 8% (20/245) with sarcomas, and 12% (13/105) with other solid tumors. The most frequent mutations were in RB1 (n = 28) and TP53 (n = 8) in patients with associated tumors. Of patients with moderate/high penetrance mutations, 30% (24/81) had unexpected tumor types, with potential therapeutic relevance in 58% (14/24) including BRCA1 n = 2, BRCA2 n = 3, RAD51D n = 1, ATM n = 1 MLH1 n = 1, MSH2 n = 1, MSH6 n = 1, PMS2 n = 3, and SUFU n = 1. Two patients received immunotherapy based on their germline finding. Conclusions: P/LP germline variants are frequently present in patients with pediatric cancer. We are contributing significantly to the cohort size of agnostic sequencing in pediatric cancers. Our experience is similar to other studies with a ~12% detection rate of moderate and high penetrance mutations. Moderate/high penetrance mutations were concordant with the patient’s cancer history in 70% of cases, higher than previously reported, likely due to an enrichment of retinoblastoma. While many mutations are identified in patients with associated tumor types, a large proportion of mutations are unexpected based on the patient’s history. Clinical actionability of these findings may include screening, risk reduction, family planning, and increasingly targeted therapies.

Targeted therapy based on germline analysis of tumor-normal sequencing (MSK-IMPACT) in a pan-cancer population

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Background: Tumor mutational profiling for identification of somatic alterations for targeted treatment is increasingly being performed in advanced cancer patients (pts). We sought to assess the clinical utility of germline mutation profiling for targeted therapeutic interventions in a pan-cancer patient population. Methods: All pts who had germline genetic testing through a prospective protocol via a next-generation sequencing panel (MSK-IMPACT) were identified (N=11,975) from 2015-5/2019. The medical record of pts with likely pathogenic/pathogenic germline (LP/P) alterations in genes with known therapeutic targets were reviewed to identify germline-targeted treatment either in a clinical or research setting. Results: We identified 2,043 (17.1%) pts who harbored LP/P variants in a cancer predisposition genes including 777 (6.5%) in genes with potentially targetable therapeutic implications: 416 BRCA1/2, 149 DNA mismatch repair genes (Lynch syndrome, LS), 122 ATM, 45 PALB2, 26 RAD51C/D, 7 RET, 4 TSC, 3 PTCH1, 2 ALK, 1 EGFR, 1 MET and 1 KIT. Of those with advanced disease (n=554), 45.3% received targeted therapeutic treatment (Table) including 50.9% BRCA1/2, 58.3% LS (67.4% of microsatellite-high LS cases), 41.7% PALB2, 36.8% RAD51C/D and 19.3% ATM carriers. Of patients receiving a poly (ADP-ribose) polymerase inhibitor (PARP-I) in the setting of a BRCA1/2 mutation, 55.1% had breast or ovarian cancer; however, 44.8% had other tumors, including pancreas, prostate, bile duct, gastric, wherein the drug was given in a research setting. Among PALB2 pts receiving PARP-Is, 53.3% (8/15) had breast or pancreas cancer; 46.7% had cancer of the prostate, ovary or unknown primary. Conclusions: In our pan-cancer analysis, 6.5% of pts harbored a targetable germline variant highlighting the importance of germline analysis in advanced cancer pts for selection of both FDA-approved treatments and clinical trial participation with germline-targeted therapeutics. [Table: see text]

Characterization of patients with multiple primary tumors

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Background: 17% of patients (pts) with a cancer diagnosis in the U.S. have a prior malignancy. We sought to characterize pts with multiple (≥2) primary cancers (MPC) & identify potential drivers of cancer risk to guide management. Methods: Pts prospectively consented (1/2013-2/2019) to tumor-normal sequencing via custom targeted NGS panel. A subset consented to testing of >76 germline cancer predisposition genes. IARC 2004 rules for defining MPC were applied.Age adjusted gender specific standardized incidence ratios (SIR) for cancer event combinations occurring in at least 5pt were calculated using R statistical package. Results: Of 24417 pts sequenced, 4341 had MPC (18%). (Table) 3465 (80%) had 2, 4% had >4 cancers. Cancer pairs where SIR of 2nd cancer was higher than expected included: colon-colon, prostate-pancreas, bladder-prostate in men & lung-lung, breast-pancreas, thyroid-pancreas in women. 1580 (36%) pts had germline testing; 324 (21%) had 361 pathogenic/likely pathogenic (P/LP) variants (vts). Of these, 157 (48%), 66(20%), pts had high, moderate penetrance vts. The remainder had low penetrance, recessive or vts of uncertain utility. Of pts with high penetrance vt, 132 (84%) had at least one tumor type concordant with germline findings. Conclusions: 18% of pts in this cohort had MPC. There was a significant excess over expected incidence in some cancer combinations. Of pts with germline testing, 21% had a P/LP vt, with most (69%) being high or moderate penetrance. Assessment for loss of heterozygosity in tumor & germline sequencing of the full MPC cohort is ongoing. [Table: see text]

Impact of treatment line on outcomes with salvage ipilimumab + nivolumab in metastatic renal cell carcinoma (mRCC)

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Background: With the approval of ipilimumab plus nivolumab (I+N) and other immune checkpoint blockade (ICB) based combinations in the first-line setting, the role of I+N for salvage is of high interest for treatment sequencing, yet data is limited. Methods: We conducted a retrospective review of mRCC patients (pts) treated with I+N in the second-line (2L) and beyond settings at MSKCC between 2013-2019. Pt demographics, treatment history and toxicity were compiled. IMDC-risk status was calculated at I+N therapy start. Time to treatment failure (TTF) was defined as earliest date of clinical progression, therapy change or death, and overall survival (OS) was estimated by Kaplan-Meier method. Results: 36 pts received I+N in the 2+L setting, including 31/36 with clear-cell histology. Evaluable IMDC-risk at I+N start was favorable in 1/35 and intermediate-poor in 34/35 pts. The most common 1L therapies were anti-VEGF (22/36) and VEGF + ICB (6/36). 11/36 pts had ICB treatment exposure prior to I+N therapy. I+N therapy in the 2L, 3L and 4L was in 21/36, 8/36 and 7/36 pts, respectively, and 7/36 pts continue I+N at data cut-off. 8/36 pts discontinued I+N due to toxicity, 20/36 pts discontinued therapy due to disease progression, and 1 pt discontinued per pt preference. Cohort median OS was 14.8 months (95%CI: 4.2-44). Overall median TTF was 5.0 months (95%CI: 2.9-14.4), and TTF per 2L, 3L and 4+L was 8.3, 8.9 and 2.5 months, respectively. The number of patients who completed all 4 I+N induction cycles in the 2L, 3L, and 4+L was 11/21 (52%), 5/8 (63%), and 1/7 (14%). The number of patients who subsequently received nivolumab maintenance therapy after induction was 16/21 (76%) in the 2L, 1/8 (13%) in the 3L, and 0/7 (0%) in 4+L. Conclusions: With emerging treatment options for mRCC, this study reveals activity and safety for I+N in 2+L settings. In this limited cohort, completion of induction ipilimumab and use of maintenance nivolumab decline in later-line settings, suggesting limitations as salvage therapy. [Table: see text]

Genomic biomarkers of response to lenvatinib/pembrolizumab (Len/Pembro) in patients with advanced renal cell carcinoma

733

Background: A phase 1b/2 clinical trial indicated that len/pembro shows promise in the treatment of renal cell carcinoma (RCC) in both PD-1/PD-L1 immune checkpoint blockade (ICB)-naïve and pretreated patients (NCT02501096). The combination is being further investigated in a phase 3 clinical trial in RCC (NCT02811861). Tumor antigen presentation depends on multiple factors, including HLA diversity, which can be measured by HLA evolutionary divergence (HED). HED quantitates the capacity of a patient’s HLA genotype to present different peptide antigens. This study is investigating the genomic components of tumor antigen presentation in ICB-naïve patients who have RCC and are treated with len/pembro. Methods: Whole exome sequencing (WES) was performed on pretreatment tumor-derived DNA. Somatic mutations, tumor mutation burden (TMB), neoantigen (NA) load, germline HLA zygosity and somatic loss of heterozygosity (LOH), and HED were correlated with objective response rate (ORR) and progression-free survival (PFS). An updated clinical cutoff was March 29, 2019. Results: Twenty four (80%) of 30 ICB-naïve patients underwent WES. A top-quartile cutoff was used. Increased mean HED was associated with improved PFS, while HLA homozygosity or LOH trended toward worse PFS. Loss-of-function mutations in PBRM1 (PBRM1 LOF) trended toward improved PFS. However, TMB and NA load were not correlated to PFS. No genomic biomarkers were correlated to ORR. Conclusions: Increased HLA diversity was associated with improved PFS, while decreased HLA diversity may be associated with worse PFS. PBRM1 mutation may be associated with improved PFS; however, TMB and NA load were not correlated to outcomes. These findings warrant further examination in larger datasets to rule out possible artifacts from multiple testing in a small cohort. Clinical trial information: NCT02811861. [Table: see text]

Response to systemic therapy in patients with metastatic fumarate hydratase (FH) deficient renal cell carcinoma (RCC)

686

Background: FH-deficient RCC (FHRCC) is characterized by unique pathologic features and lack of FH staining on immunohistochemistry (IHC). Most cases are associated with germline FH mutations and poor prognosis, but there is limited data on the efficacy of systemic therapy. Methods: Patients with metastatic FHRCC, defined by presence of FH germline or somatic mutation with loss of FH by IHC [FH and 2-succino-cysteine (2SC)], were identified from an institutional database. Clinical and treatment data was obtained from electronic records. The primary outcome was best objective response rate to first, second or third-line systemic therapy by blinded investigator RECIST v1.1 assessment. Results: 32 patients (median age 46; range 20-74; M:F, 20:12) were identified. All patients had evidence of FH-deficiency by IHC, 23 (72%) had germline FH mutations, 9 (28%) had somatic only FH mutations. 20 patients (62.5%) presented with de novo metastatic disease. Most common sites of metastasis were retroperitoneal lymph nodes (82%), lung (78%) and peritoneal spread (70%); no patients developed brain metastases. Median overall survival (OS) from diagnosis of metastatic disease is 28.1 months (95% CI: 14.9, 33.8). Median follow-up is 14.8 months. 25 patients were evaluable for response to first-line therapy, 5 to second-line and 4 to third-line therapy (Table). Most common first-line therapies were combination mTOR/VEGFR (50%) and VEGFR monotherapy (20%). ORR to first, second and third-line therapy was 40%, 20% and 25%, with no complete responses. 8 patients who received IO monotherapy were evaluable; 3 had stable disease, no responses were seen. Conclusions: Patients with FHRCC show distinct patterns of disease progression with primary peritoneal spread. Although there was high ORR to VEGFR/mTOR inhibitor combinations, there were limited responses to IO monotherapy.[Table: see text]

The spinal distribution of metastatic renal cell carcinoma: Support for locoregional rather than arterial hematogenous mode of early bony dissemination

742

Background: To investigate the distribution of spinal metastasis in metastatic renal cell carcinoma (mRCC) and to explore relationships between biological and clinical factors and patterns of spinal spread. Methods: An institutional database was queried to identify patients with mRCC and spinal metastatic involvement from June 2005 – November 2018. A blinded radiologist examined all cross-sectional imaging involving the spine and scored each level for absence or presence of disease. Clinical and biologic features including primary tumor size and degree of spinal and non-bony metastatic involvement (including regional lymph node and distant deposits) were collected. Spinal distributions were evaluated by the Kolmogorov Smirnov test and compared across radiographic and clinical parameters. Results: One-hundred patients with 685 spinal levels involved by mRCC were evaluated. A nonuniform spatial distribution was observed across the cohort; a preponderance of thoracolumbar involvement was noted with the mode at L3 (p<0.001). No difference in metastatic distribution was observed in right versus left-sided tumors. Tumors <4cm compared to >7cm, patients who had distant spread versus bone-only disease, and patients with increasing number of spine levels involved (1 versus >5 levels) had a significantly different distribution (p<0.001 for all comparisons). Smaller tumor size, distant spread, and greater number of involved levels appeared to have a more uniform distribution of spinal metastasis. Conclusions: These data support a dominant locoregional as opposed to arterial hematogenous mechanism for the early dissemination of mRCC to the spine. This is concordant with the theory of the valveless Batson plexus acting as a conduit for such spread, as the kidneys are compartmentally distinct from, but reside just anterior to the spine at L1-L3. Characterizations of the biologic molecular features contributing to osseous tropism and aggressive tumor biology (as seen in the subset of patients with uniform spread, such as outlier patients with small tumors), have implications for surveillance and are an area of active investigation.

Prevalence and landscape of actionable genomic alterations in renal cell carcinoma

616

Background: We report our experience with next-generation sequencing to characterize the prevalence and genomic landscape of actionable genomic alterations in renal cell carcinoma (RCC). Methods: A query of our institutional clinical sequencing database was performed to include tumor samples sequenced across all cancers. Actionable alterations with clinical or biologic evidence supporting an association with response to targeted therapy were stratified by level of evidence using an oncology knowledge database (OncoKB). Results: Data from 35,668 patients was included, and the 15 cancer types with the highest prevalence of actionable alterations were selected for subsequent analysis (28,027 patients). Of these cancers, RCC ranked 13th in prevalence of actionable alterations. Of 708 RCC samples included, 259 (37%) were from metastatic sites. However, of the remaining 449 primary samples, 208 (29%) belonged to patients who had metastatic disease at the time of sequencing. Although 69% of patients with any RCC harbored at least one known oncogenic mutation, only 90/687 (13%) harbored alterations for which compelling clinical data currently exist to justify the use of a standard or an investigational agent (levels of evidence 1 to 3B). This represents an increase from the previously reported prevalence (5% in 2017). The most common histologic subtype, clear cell RCC harbored the vast majority of actionable alterations (52/421; 12%). Regarding the specific genes that harbor these alterations, 31 level 2A alterations were identified, all of which were TSC1/TSC2 mutations; 30 level 2B alterations were identified, of which PIK3CA (22) and BRCA1/BRCA2 (5) mutations were most common; 11 level 3A alterations, all of which were MTOR mutations, and 8 level 3B alterations, of which AKT1 (4) mutation was most common. Conclusions: Although the prevalence of actionable mutations in RCC seems to have doubled in recent years, the role of genetic testing in identifying candidates for targeted therapy in RCC is currently limited relative to other cancer types, emphasizing the need for additional research in this area to further inform targeted therapy decisions.

Defining the genetic evolution of epigenetic alterations in bladder cancer

529

Background: Large-scale efforts have sought to define the genomic landscape of urothelial carcinomas of the bladder with the goal of identifying novel therapeutic targets. Many bladder cancers harbor mutations in genes that regulate chromatin state, such as KDM6A, ARID1A and KMT2D. There remains uncertainty as to the timing at which alterations in chromatin modifying genes (CMG) arise during the evolution of urothelial cancer. Methods: We leveraged a prospective genomic profiling initiative to characterize driver alterations in urothelial cancer. To define the timing at which mutations arose during disease pathogenesis, we performed whole exome (WES) or targeted sequencing analysis of matched pairs of primary and metastatic tumors. Results: CMG mutations were identified in 76% of UC samples in the prospective MSK-IMPACT tumor sequencing cohort (N=1057); most frequent in KDM6A (31%), KMT2D (28%) and ARID1A (27%). Comparison of primary low-grade (N=65), high-grade (N=742) and metastatic (N=250) samples revealed KDM6A, FGFR3 and KMT2C were more frequently mutated in low-grade tumors. WES and targeted sequencing of 63 matched pairs demonstrate a high degree of concordance among likely oncogenic mutations. Notably, 100% (18/18) of pairs were concordant for mutations in KDM6A suggesting that, when present KDM6A mutations arise early during tumor development. Mutations in ARID1A were present only in the metastatic samples of a subset of tumors (29%) suggesting that ARID1A mutations arise later in disease pathogenesis. Several additional oncogenic drivers were found in only the metastatic sample ( FGFR3, TSC1, PIK3CA) of select tumor pairs. Conclusions: Primary and metastatic pairs were largely concordant for known and likely oncogenic mutations. Evolutionary analysis of sequencing data suggested that KDM6A mutations arise early in tumor development whereas ARID1A mutations were enriched and present only in the metastatic samples of a subset of patients. Despite the high frequency of FGFR3 mutations in low grade tumors, discordance of FGFR3 mutational status was observed in small fraction of patients suggesting that profiling of metastatic tumors or cell free DNA would be preferable to identify patients for FGFR inhibitor therapy.

Association of body mass index (BMI) with clinical outcomes in 203 metastatic clear cell renal cell carcinoma (ccRCC) patients (pts) treated with immuno-oncology (IO) agents

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Background: Obesity is a known risk factor for the development of ccRCC. For malignant melanoma, higher BMI was recently associated with improved outcomes to IO therapy (McQuade, Lancet Onc, 2018), a potential explanation being an obesity-associated inflammation effect. The association of BMI and clinical outcomes in mccRCC pts treated with IO therapy is unknown. Methods: Baseline characteristics and outcomes on therapy were retrospectively collected for pts with mccRCC who received IO-only regimens for at least 4 weeks at our institution. BMI and IMDC risk categories were determined for all pts at IO initiation. The log-rank statistic was used to test the associations between BMI with overall survival (OS) and progression free survival (PFS) and the chi-square test for the association with objective response rates (ORR). Results: Of the 203 eligible pts, 31% were normal weight, 36.5% were overweight, and 32.5% were obese. 24% of pts received IO as first line treatment. IMDC favorable vs intermediate/poor risk was 11 vs 89% in normal weight pts, 20 vs 80% in overweight pts and 20 vs 80% in obese pts. Median follow up time for survivors was 28.6 months (3.4-88). Obese and overweight pts experienced longer OS than those who were normal weight (P=0.01) (normal weight vs. obese, HR 2.0, 95% CI 1.20-3.37). However, this association became non-significant after adjusting for IMDC risk. RECIST evaluations were available for 107 pts. A higher ORR was seen in obese (41%) compared to overweight (15%) or normal weight (28%) pts (P=0.03). We found no association between BMI and PFS. Findings are summarized in the table below. Conclusions: In mccRCC pts treated with IO, obesity associates with superior outcomes, but does not appear to be independent of IMDC risk score. Research into the underlying mechanisms of obesity as a possible biomarker of IO clinical benefit is warranted. [Table: see text]

Alterations in DNA damage repair (DDR) genes and outcomes to systemic therapy in 225 immune-oncology (IO) versus tyrosine kinase inhibitor (TKI) treated metastatic clear cell renal cell carcinoma (mccRCC) patients (pts)

551

Background: Loss of function alterations in DDR genes including core components of mismatch repair and homologous recombination deficiency pathways are associated with tumorigenesis and may determine benefit from IO therapies as shown in colon cancer. The significance for standard IO and TKI treatments in mccRCC is unknown. Methods: Genomic data and treatment outcomes were retrospectively collected for two large cohorts of mccRCC: pts treated with pure IO therapy (cohort 1); and pts receiving first-line TKI (cohort 2). Tumor and germline DNA was subject to targeted panel testing across >400 genes of interest, including 34 DDR machinery genes. Presence of truncating mutations, deletions and functionally validated missense mutations identified individual patient as ‘DDR altered’ (DDRa). Tumor mutational burden (TMB) was inferred for all pts. Non-parametric tests were applied to determine association between DDR status, TMB and treatment outcomes. Results: 225 pts were included (cohort 1=107, cohort 2=118), 37 (16%) were DDRa. Most commonly altered genes were ATM (n=8, 4%) and CHEK2 (n=8, 4%). DDR germline alterations were seen in 12 pts (5%). Median TMB was 4.1 per megabase (range: 0-21.7), and higher TMB (≥ median) was associated with being DDRa (Fisher’s exact, p=0.03). DDRa status correlated significantly with longer overall survival (OS) in the IO cohort (HR 0.29, logrank p=0.04) but not in the TKI cohort (HR 0.74, logrank p=0.44). We found no interaction between objective response and DDR status in either cohort. Conclusions: Loss of function in DDR genes was associated with superior OS in IO-treated but not in TKI-treated RCC pts. Possible underlying mechanisms beyond increase in TMB observed here deserve further study. [Table: see text]

Tumor testing in men with prostate cancer to predict for germline DNA-damage repair mutations

229

Background: Current guidelines recommend genetic testing for patients (pts) who have BRCA1/2 mutations on tumor-only testing, where germline is not subtracted. The clinical utility of this approach, and possible inclusion of other DDR genes associated with cancer susceptibility, has not been examined in men with prostate cancer. Methods: Pts with mostly advanced prostate cancer were prospectively enrolled to a matched tumor-germline DNA sequencing protocol and consented for disclosure of germline results. Germline analysis was done with an institutional, CLIA-certified next generation sequencing (NGS) platform (MSK-IMPACT) and analyzed for likely pathogenic or pathogenic germline mutations in at least 76 cancer susceptibility genes. Clinical data was retrieved from the medical record. We report on the frequencies in the germline and in the tumor of a subset of DDR genes. Results: 1243 men had analysis of both germline and tumor. Median age 64 (range 35-90). 12% had a second malignancy and 40% reported a relative with prostate cancer. 19% were of Ashkenazi Jewish (AJ) descent. 330 (27%) had any mutation in BRCA1/2, ATM, CHEK2, PALB2, RAD51C, RAD51D, MSH2, MSH6, MLH1, PMS2. 127 (10%) had a germline mutation, of which 36% were AJ founder mutations. For each gene, the percentage of mutations found in germline and tumor is shown in the table. Conclusions: Of prostate cancer pts found to have any DDR mutation on tumor-germline testing, 29% had a germline mutation. Proportion of germline mutations was highest for PALB2, CHEK2 and BRCA2. These findings not only support germline testing when BRCA1/2 mutations are found tumor-only sequencing, but also support germline testing when other DDR mutations are seen. Clinical trial information: NCT01775072. [Table: see text]

Genomic biomarkers of response to nivolumab/ipilimumab (nivo/ipi) and nivolumab (nivo) monotherapy in 108 patients with advanced renal cell carcinoma

641

Background: Both the combination of nivo/ipi and nivo monotherapy have shown efficacy across multiple malignancies including clear cell Renal Cell Carcinoma (ccRCC). Biomarkers such as tumor mutation burden (TMB) are prognostic in other malignancies, however, remain unvalidated in ccRCC. This study investigates genomic biomarkers associated with nivo/ipi and nivo clinical response. Methods: Whole exome sequencing (WES) was performed on pretreatment tumor derived DNA from nivo/ipi and nivo treated patients from MSKCC and publicly available WES datasets (Miao D, Science, 2018, 359: 6377). Somatic mutations, TMB, neoantigen load (NA), and HLA zyogosity were correlated to objective response rate (ORR), progression free survival (PFS), and Overall Survival (OS). Alterations occurring in < 10% of the cohort were considered non-evaluable (NE). Results: 108 patients had tumors studied; 32 patients with nivo/ipi and 76 patients with nivo therapy. No individual factors showed significant correlations to ORR or both PFS and OS. In the combined cohort, homozygosity at HLA-C was associated with shorter OS (HR=2.55 95% CI 1.17-5.57; P=0.02). In the nivo/ipi cohort, TMB (HR=0.36 95% CI 0.16-0.84; P=0.02) and NA (HR=0.43 95% CI 0.19-0.98; P=0.04) were associated with longer PFS. Conclusions: Increased TMB and NA load may predict for improved outcomes, and homozygosity at HLA loci may predict for worse outcomes. The predictors of response to nivo may not be generalizable to nivo/ipi. To rule out artifacts of multiple testing in a small cohort, validation in a larger dataset is necessary. [Table: see text]

The impact of PBRM1 mutations on overall survival in greater than 2,100 patients treated with immune checkpoint blockade (ICB)

666

Background: PBRM1 is the second most commonly mutated gene in clear cell renal cell carcinoma (ccRCC). We have previously shown favorable outcomes in PBRM1-mutated ccRCC tumors treated with vascular endothelial growth factor (VEGF) inhibitors. Recent data suggested PBRM1 mutations may sensitize ccRCC and non RCC malignancies to ICB therapy. We queried the impact of PBRM1 loss on overall survival (OS) across 2,152 patients treated with ICB. Methods: PBRM1 mutations were assessed in metastatic ccRCC patients who received first line (n = 82) or second line (n = 61) ICB or ICB/VEGF combinations. Additionally, 41 cohorts of non-RCC malignancies treated with ICB and combination (n = 2,009) were analyzed. Mutations were assessed by next generation targeted sequencing using archival tissue. Association of mutation status and overall survival (OS) was tested by multivariate Cox regression analysis (MVA) and adjusted for tumor mutation burden (TMB), copy number alterations (CNA), loss of function(LOF) mutations (non RCC cohort) and IMDC risk (for ccRCC patients). Results: PBRM1 mutations were not associated with improved OS in ICB the entire ccRCC cohort (HR 1.37; CI 0.79-2.4; p = 0.265), the first line (p = 0.624) or second line setting (p = 0.39) or as combination with VEGF inhibitors (p = 0.2). Several RCC subgroups were investigated (see Table at bottom). In the non-RCC cohorts (n = 2,009) PBRM1 mutations were not significantly associated with OS on univariate analysis (HR = 0.73, p = 0.22 for LOF and HR = 0.84,p = 0.34 for non LOF), and remained insignificant after adjusting for TMB, total CNA, and drug class (CTLA4, PD-1/PDL-1 and combinations) (HR = 1.07, p = 0.78 for LOF and HR = 1.08,p = 0.67 for non LOF). Conclusions: Neither in ccRCC nor in the pan-cancer cohort did PBRM1 mutations appear to be associated with improved overall survival with ICB therapy.[Table: see text]

Immune checkpoint inhibitors in MITF family translocation renal cell carcinomas and genetic correlates of exceptional responders

Background

Microphthalmia Transcription Factor (MITF)family translocation renal cell carcinoma (tRCC) is a rare RCC subtype harboring TFE3/TFEB translocations. The prognosis in the metastatic (m) setting is poor. Programmed death ligand-1 expression was reported in 90% of cases, prompting us to analyze the benefit of immune checkpoint inhibitors (ICI) in this population.

Patients and methods

This multicenter retrospective study identified patients with MITF family mtRCC who had received an ICI in any of 12 referral centers in France or the USA. Response rate according to RECIST criteria, progression-free survival (PFS), and overall survival (OS) were analyzed. Genomic alterations associated with response were determined for 8 patients.

Results

Overall, 24 patients with metastatic disease who received an ICI as second or later line of treatment were identified. Nineteen (82.6%) of these patients had received a VEGFR inhibitor as first-line treatment, with a median PFS of 3 months (range, 1–22 months). The median PFS for patients during first ICI treatment was 2.5 months (range, 1–40 months); 4 patients experienced partial response (16,7%) and 3 (12,5%) had stable disease. Of the patients whose genomic alterations were analyzed, two patients with mutations in bromodomain-containing genes (PBRM1 and BRD8) had a clinical benefit. Resistant clones in a patient with exceptional response to ipilimumab showed loss of BRD8 mutations and increased mutational load driven by parallel evolution affecting 17 genes (median mutations per gene, 3), which were enriched mainly for O-glycan processing (29.4%, FDR = 9.7 × 10^− 6).

Conclusions

MITF family tRCC is an aggressive disease with similar responses to ICIs as clear-cell RCC. Mutations in bromodomain-containing genes might be associated with clinical benefit. The unexpected observation about parallel evolution of genes involved in O-glycosylation as a mechanism of resistance to ICI warrants exploration.

Outcomes of metastatic chromophobe renal cell carcinoma (ChRCC) with sarcomatoid features (SF)

678

Background: ChRCC makes up 5-10% of RCC subtypes and is generally thought to confer favorable prognosis. Presence of SF on histologic review can occur in any RCC subtype and is considered a hallmark of aggressive disease. We assessed outcomes in a cohort of patients (pts) with metastatic ChRCC and SF (sChRCC). Methods: Baseline clinical features and details on treatment were collected for pts with newly diagnosed metastatic sChRCC evaluated at Memorial Sloan Kettering Cancer Center (MSKCC) between 2002-17. Overall survival (OS) was calculated for all patients and time to treatment failure (TTF) for those who received first-line therapy at MSKCC. Next generation sequencing (NGS) with MSK-IMPACT was performed in a subset of pts. Results: 27 pts with newly diagnosed metastatic sChRCC were identified; other clinical features are summarized below ( table). 2 pts never received first line therapy based on poor performance status. 16 were treated at MSKCC and received a median of 2 lines of systemic therapy. First line agents included sunitinib (n = 6), pazopanib (n = 2), temsirolimus (n = 2), everolimus + bevacizumab (n = 2), sunitinib + gemcitabine (n = 2) and interferon alpha (n = 2) with median TTF of 2.1 months (0.9-14.5). Across the entire cohort (n = 27), median OS was 7.9 months (95% CI 4.2-11.2) with estimated 1 year OS rate of 25%. By comparison, a cohort of 67 pts with metastatic ChRCC lacking SF also treated at MSKCC 2002-17 achieved median OS of 38.1 months, (HR 4.6; 95% CI: 2.6-8.3; p < 0.001). In the 6 sChRCC pts with NGS analysis, TP53 (n = 4), PTEN (n = 2) and CHEK2 (n = 2) were the most frequently altered genes. Conclusions: Outcome for pts with metastatic sChRCC was poor in contrast to pts with ChRCC lacking SF. The lack of benefit observed across various classes of systemic agents warrants study of underlying biology and novel agents. [Table: see text]

Everolimus (E) plus bevacizumab (B) is effective first-line treatment for patients (pts) with advanced renal cell carcinoma (RCC) with papillary features (PF): Results from a phase II trial

627

Background: We previously reported on a phase II trial of E+B across various non-clear cell RCC histologies and observed significant activity among pts with papillary or unclassified RCC ( uRCC ) with PF (objective response rate [ORR] 39%, median progression-free survival [PFS] 12.9 months [m]; Voss, JCO, 2016). An expansion cohort limited to these two histologies was conducted to confirm the efficacy of E+B. Methods: E + B was administered at standard doses until progressive disease (PD) or intolerance to therapy. The current analysis included 19 pts with pRCC or uRCC with PF in the initial cohort and 20 pts in the expansion cohort (total n=39). The primary endpoint was 6 month PFS with secondary endpoints of ORR, median PFS, and overall survival (OS). Correlative analyses included next generation sequencing (NGS) from tumor and germline across >341 genes of interest. Results: Of 39 pts, 24 had uRCC with PF, 14 had papillary RCC, and 1 had translocation RCC with PF. Among 37 evaluable pts, the ORR was 35%; 43% for uRCC with PF and 23% for papillary RCC. Six-month PFS for all 39 pts was 78%; 82% for uRCC with PF and 68% for papillary RCC. Median PFS was 13.7m; 13.7m for uRCC with PF and 8.4m for papillary RCC (Table). With median followup of 17.6m, median OS is 33.9m. Toxicity with E+B was similar to previous reports. 33 of 39 pts had NGS performed and partial responses were observed across a wide spectrum of genomic alterations, including several recurrently seen in papillary RCC variants such as mutations in FH, MET, NF2, and ARID1a. Conclusions: The expansion cohort confirms the activity of E+B for pts with advanced papillary RCC or uRCC with PF with superior ORR, PFS, and OS compared to historical results with sunitinib for these histologies. E+B represents a new standard first-line treatment option for these pts. Clinical trial information: NCT01399918. [Table: see text]

Genomic Alterations and Outcomes with VEGF-Targeted Therapy in Patients with Clear Cell Renal Cell Carcinoma

Background: Mutations in VHL, PBRM1, SETD2, BAP1, and KDM5C are common in clear cell renal cell carcinoma (ccRCC), and presence of certain mutations has been associated with outcomes in patients with non-metastatic disease. Limited information is available regarding the correlation between genomic alterations and outcomes in patients with metastatic disease, including response to VEGF-targeted therapy.

Objective: To explore correlations between mutational profiles and cancer-specific outcomes, including response to standard VEGF-targeted agents, in patients with metastatic cc RCC.

Methods: A retrospective review of 105 patients with metastatic ccRCC who had received systemic therapy and had targeted next-generation sequencing of tumors was conducted. Genomic alterations were correlated to outcomes, including overall survival and time to treatment failure to VEGF-targeted therapy.

Results: The most frequent mutations were detected in VHL (83%), PBRM1 (51%), SETD2 (35%), BAP1 (24%), KDM5C (16%), and TERT (14%). Time to treatment failure with VEGF-targeted therapy differed significantly by PBRM1 mutation status (p = 0.01, median 12.0 months for MT versus 6.9 months for WT) and BAP1 mutation status (p = 0.01, median 6.4 months for MT versus 11.0 months for WT). Shorter overall survival was associated with TERT mutations (p = 0.03, median 29.6 months for MT versus 52.6 months for WT) or BAP1 mutations (p = 0.02, median 28.7 months for MT versus not reached for WT).

Conclusions: Genomic alterations in ccRCC tumors have prognostic implications in patients with metastatic disease. BAP1 and TERT promoter mutations may be present in higher frequency than previously thought, and based on this data, deserve further study for their association with poor prognosis.

Mismatch repair (MMR) detection in urothelial carcinoma (UC) and correlation with immune checkpoint blockade (ICB) response

4511

Background: High mutation burden correlates with response to ICB in UC. Loss of function alterations or epigenetic silencing of MMR genes results in MMR deficient (MMR-D) UC, leading to a microsatellite instability (MSI) mutation signature. We used a CLIA-certified pipeline (MSISensor) to interrogate Next Generation sequencing (NGS) data from UC tumors to identify MMR-D patients (pts). We correlated MMR-D with mutation load and response to ICB. Methods: 447 tumors from 424 UC pts underwent prospective NGS using the MSK-IMPACT exon capture assay and genomic interrogation of microsatellite (MS) sites using MSIsensor, which assesses the number/length of MS within the targeted regions of tumor-normal sample pairs. Loci are considered unstable (somatic) if k-mer distributions are significantly different between tumor and matched normal using a standard multiple testing correction of χ2 p-values. The fraction of unstable sites is reported as an MSIsensor score. MSI high tumors have scores >10 while <3 are denoted MS stable. Scores from 3-10 were categorized as MS intermediate. Results: Thirteen pts (3%) had an MSI score >10 and a median mutation count of 52 (36.5-73.5) vs 8 (5-13) in 410 non-MMR-D pts (p<0.01). Ten pts (71%) had upper tract UC. Of 9 pts with germline sequencing performed, 8 (89%) had heritable loss of function mutations in MMR proteins (Lynch syndrome, LS). One pt had a somatic MSH2 mutation. Fifteen pts had MS scores from 3-10: 3 had LS, one a BRCA1 germline alteration, and 9 did not have germline testing available. Two pts with MSI scores <3 had extremely high mutation loads (213 and 414) and both had POLE mutations. Five pts received ICB therapy for metastatic and all achieved near-complete or complete responses. No MMR-D pt has died at 27 months follow-up vs 125 non-MMR-D pts (p=0.014). Conclusions: The MSI Sensor assay can discriminate MSI high from MMR proficient UC. While rare, MMR-D UC is characterized by a high mutation load, strong association with Lynch syndrome, and durable responses to ICB, similar to data in colon cancer. An MMR-D signature should trigger genetic testing for Lynch syndrome. ICB should be considered early in the treatment course of patients with MMR-D metastatic UC.

Discovery and prevalence of cancer-susceptibility germline mutations (Mts) in patients (Pts) with advanced renal cell carcinoma (aRCC)

4524

Background: About 5% of RCC is thought to be familial, but recent studies suggest this may be an underestimate (Int. J. Cancer;100:476). We studied the prevalence of germline cancer-susceptibility mts in pts with aRCC. Methods: Pts with aRCC (stage III or IV), unselected for suspicion of an inherited cancer syndrome, were offered germline testing for 76 cancer-associated genes between 10/2015 and 12/2016. Germline sequencing was done as part of MSK-IMPACT, a matched tumor-normal next-generation sequencing platform. Results: 203/213 pts accepted testing (median age 55, range 13-55) of whom 73% had clear cell RCC (ccRCC), 92% had metastases, 20% were early onset (≤46 yrs at diagnosis), 9% had a family history of RCC, 6% multifocal RCC at diagnosis, and 15% ≥2 primary malignancies. Pathogenic/likely pathogenic mts were found in 35 pts (17%): 12 (6%) with mts in genes associated with familial RCC; 10 (5%) mts in high/moderate penetrance genes not linked to RCC (Table).13 (6%) had mts in genes of low/uncertain penetrance or for autosomal recessive disease. Mts were present in 15% of ccRCC and 19% of non-ccRCC. Mts were not more common in pts with early onset, family history, multifocal RCC, or ≥2 malignancies (p>0.1 for each by Fisher’s exact test). Notably, 4/12 pts with mts in familial RCC genes did not meet the American College of Medical Genetics (ACMG) criteria for testing (1 each VHL, BAP1, SDHA, FH). Prevalence of CHEK2 mts was compared to population databases (ExAC); CHEK2 conferred a relative risk of 10.9 (p< 0. 002; CI=3.9-24.7) for RCC. Conclusions: 17% of aRCC pts had a germline mutation in a cancer-associated gene of which 33% of the high penetrance RCC germline mts were not identified using standard clinical criteria, providing rationale for broad testing. Once the increased risk is confirmed, CHEK2 should be included in RCC genetic testing. [Table: see text]

Cancer predisposing germline mutations in patients (pts) with urothelial cancer (UC) of the renal pelvis (R-P), ureter (U) and bladder (B)

4510

Background: Urothelial cancers (UC) are suspected to have a substantial hereditary component, but other than highly penetrant genes such as those in mismatch-repair pathway (e.g. MSH2) typically associated with R-P/U primaries, heritable gene mutations have not been systematically studied. We sought to investigate the prevalence of known cancer pre-disposing germline mutations in pts with UC originating from all sites within the urinary tract. Methods: Pts with R-P, U and B primaries, unselected for suspicion of inherited cancer syndrome, were prospectively enrolled from medical oncology and urology clinics to a germline sequencing protocol from June 2016 to January 2017. Germline gene analysis was performed in a CLIA-certified lab using a next generation sequencing (NGS) platform (MSK-IMPACT) that analyzes tumor-normal DNA pairs. The germline gene panel consisted of 76 genes associated with hereditary cancer predisposition. Results: As of January 24, 2017, 101 pts have NGS results available, with median age 63 (31-87), 76% male, 24% female. Primary sites were B (67%), R-P/U (31%), or both (3%). 73% had organ-confined disease and 27% had metastases. 8% had early onset (≤45 yrs at diagnosis), 10% had a family history of UC, 25% had documented non-UC cancers. 25 pathogenic or likely pathogenic (P-LP) mutations were identified in 22 patients. P-LP mutations were present in 29% of pts with R-P/U primaries and 18% of pts with B primaries. 12 DNA damage response gene alterations were found (4 CHEK2, 3 BRCA1, 2 BRCA2, 1 ATM, 1 BRIP1, 1 NBN) and 8 in Lynch syndrome associated genes (5 MSH2, 2 MSH6, 1 MLH1). Other mutations include 2 APC, 1 TP53, and 1 FH. Notably 3 pts had 2 alterations each ( MSH6/ APC, BRCA2/ APC, BRCA1/ CHEK2). 9/22 pts with P-LP mutations did not meet American College of Medical Genetics criteria for genetic screening. Conclusions: 22% of UC pts had a germline mutation in a cancer-associated gene. There was an unexpectedly high frequency of pts with DNA-repair pathway mutations. Active accrual is ongoing to define the full spectrum of alterations. These results have profound implications for genetic counseling and screening and further studies are warranted.

Dynamics of immune-mediated thyroid dysfunction in patients with advanced renal cell carcinoma receiving checkpoint inhibitor therapy

e16071

Background: Checkpoint inhibitors (CPI) are quickly gaining relevance in the management of metastatic renal cell carcinoma (RCC). Treatment is generally well tolerated, but immune-induced thyroid dysfunction (TD) is reported in up to 10% of patients (pts) across trials. The dynamics of this phenomenon are undefined; hence there are no proposed standards for endocrine surveillance on therapy. Here we report on a cohort of RCC pts treated with CPI at Memorial Sloan Kettering Cancer Center with serial prospective assessment of thyroid function on therapy. Methods: Thyroid function tests (TFT) were assessed at baseline and serially on therapy. We recorded trends for hyper- and hypothyroidism and determined median time to development of TD by standard statistical methods. T4 replacement therapy was investigated by individual chart review. The association of TD with outcomes on CPI therapy was assessed by non-parametric tests. Results: Of 59 pts with serial TFT assessment, 20 were hypothyroid and 39 were euthyroid at baseline. 50% of previously hypothyroid pts required adjustment of T4 dosage. Thirteen of 39 euthyroid pts (36%) developed new TD requiring thyroid replacement. TD occurred early (median time to onset: 1.4 months, range 0.9-9.6), and in six of the 13 pts (46%), transient thyroiditis preceded hypothyroidism. None of the pts with thyroiditis required treatment, and the median duration from onset of thyroiditis to development of hypothyroidism was 1.5 months (range 0.7-2.8). All pts with hypothyroidism required replacement therapy; none required discontinuation of immunotherapy due to TD. TD was not associated with difference in objective response rate (fisher’s exact, p = 0.163), regression in target lesions (wilcoxon rank-sum, p = 0.135), or PFS (log rank p = 0.8214). Conclusions: TD is common in RCC pts receiving CPI therapy. In this cohort, onset of TD was early, thyroiditis was always transient, and no new cases were detected beyond 10 months. Confirming these findings in larger cohorts will provide meaningful data to guide management of TD when using this new class of agents outside of clinical trials.

The genomic landscape of metastatic non-clear cell renal cell carcinoma

474

Background: Non-clear cell renal cell carcinoma (nccRCC) encompasses about 20% of RCC cases and includes a number of subtypes that vary clinically and molecularly. Compared to ccRCC, these tumors have more limited sensitivity to conventional anti-VEGF agents and mTOR inhibitors, and there is clear need for better therapies. Analysis of genomic alterations in potentially targetable pathways may lead to novel therapeutic development strategies. Methods: We retrospectively analyzed tumors from 112 patients with metastatic nccRCC with targeted next-generation sequencing (NGS) across a panel of >340 cancer-relevant genes. Matched tumor and normal was used to facilitate somatic calling. We report on recurrent alterations observed for nccRCC variants. Results: Median age was 53 years (range 12-77), 67% were male; 47% presented with metastatic disease and 53% with localized disease that later metastasized. NGS was performed on tissue from primary tumors (57%) or metastatic sites (43%). Subtype classifications included unclassified (44%), papillary (21%), chromophobe (13%), translocation (12%), and other (9%). The most frequently altered genes by subtype are included in table. 36% of unclassified or papillary tumors had a mutation in a putative driver gene amenable to targeted therapies, including MET, NOTCH1, SMARCB1, TSC1, TSC2, PIK3CA, and FGFR3. 3 chromophobe tumors and 1 translocation tumor had a mutation in a potentially targetable pathway. Conclusions: The mutation profiles of metastatic nccRCC vary by papillary, chromophobe, and translocation subtype, with unclassified tumors most approximating papillary subtype. Unclassified and papillary subtypes harbor frequent mutations in potentially targetable pathways that merit further investigation. [Table: see text]