Choueiri, Toni K.

SNF'ing out antitumor immunity Immune checkpoint inhibitors induce durable tumor regressions in some, but not all, cancer patients. Understanding the mechanisms that determine tumor sensitivity to these drugs could potentially expand the number of patients who benefit (see the Perspective by Ghorani and Quezada). Pan et al. discovered that tumor cells in which a specific SWI/SNF chromatin remodeling complex had been experimentally inactivated were more sensitive to T cell–mediated killing. The cells were more responsive to interferon-γ, leading to increased secretion of cytokines that promote antitumor immunity. Miao et al. examined the genomic features of tumors from patients with metastatic renal cell carcinoma who had been treated with immune checkpoint inhibitors. Tumors harboring inactivating mutations in PBRM1 , which encodes a subunit of the same SWI/SNF complex, were more likely to respond to the drugs. Science , this issue p. 770 , p. 801 ; see also p. 745

522 Background: In the METEOR study (NCT01865747), cabo demonstrated improved progression-free survival (median 7.4 vs. 3.8 mo; HR 0.58, 95% CI 0.45–0.74; p<0.0001), OS (median 21.4 vs. 16.5 mo; HR 0.66, 95% CI 0.53-0.83, p=0.0003), and objective response rate (17% vs. 3%; p<0.0001) compared with eve in patients (pts) with advanced RCC who had received prior VEGFR TKI therapy (Choueiri NEJM 2015, Lancet Oncol 2016). Here we evaluate the impact of changes in target lesion size from baseline on OS. Methods: 658 pts were randomized 1:1 to receive cabo (60 mg qd) or eve (10 mg qd). Stratification factors were MSKCC risk group and number of prior VEGFR TKIs. Target lesion size was assessed per independent radiology review by CT/MRI scans at baseline, every 8 weeks for the first 12 months, and every 12 weeks thereafter. Three subgroups were defined by best change in target lesion size from baseline: decrease ≥30%, decrease <30%, and any increase. Results: The rate of target lesion regression was higher in the cabo arm (75%) compared with the eve arm (48%). A higher fraction of pts had a decrease ≥30% in target lesion size in the cabo arm, while a higher fraction of pts had an increase in target lesion size in the eve arm (Table). Medians for OS with cabo were not estimable (NE) (95% CI, NE‒NE), 20.8 mo (95% CI, 18.1‒NE), and 11.1 mo (95% CI, 7.6‒15.2) for the ≥30% decrease, <30% decrease, and any increase subgroups, respectively. Medians for OS with eve were NE (95% CI, 19.3‒NE), 18.0 mo (95% CI, 15.9‒20.4), and 14.0 mo (95% CI, 10.5‒16.3) for the ≥30% decrease, <30% decrease, and any increase subgroups, respectively. Median duration of follow-up for OS was 18.7 mo (IQR 16.1–21.1) for cabo and 18.8 mo (16.0–21.2) for eve. A higher proportion of pts received subsequent anticancer therapy in the any increase subgroup compared with the other subgroups. Conclusions: Cabo demonstrated a higher rate of tumor target lesion regression than eve, and greater target lesion regression was associated with improved OS in pts with advanced RCC. Clinical trial information: NCT01865747. [Table: see text]

431 Background: While targeting VEGF improves outcomes for mRCC pts, resistance invariably develops, often within the first year. Here, we describe the efficacy and safety of atezo (anti-PD-L1) with bev (anti-VEGF) and atezo monotherapy vs sun (TKI) in first-line mRCC. Methods: Treatment-naïve mRCC pts were enrolled in a hypothesis generating Ph II study (IMmotion150; NCT01984242) and randomized to atezo 1200 mg IV q3w + bev 15 mg/kg IV q3w, atezo alone or sun 50 mg PO QD 4 wk on/2 wk off. Crossover to atezo + bev after disease progression was allowed for pts receiving atezo or sun. PD-L1 expression was scored on tumor-infiltrating immune cells (IC, SP142 IHC assay). Coprimary endpoints were PFS (RECIST v1.1 by independent review [IRF]) in ITT pts and pts with PD-L1 expression on ≥ 1% of IC (PD-L1+). Results: Baseline characteristics were comparable across arms and between ITT and PD-L1+ pts. The majority of sun and atezo pts subsequently received atezo + bev. Median survival follow up was 20.7 mo. The PFS HR in ITT pts for atezo + bev vs sun was 1.00 and 1.19 for atezo vs sun. In PD-L1+ pts, the PFS HR for atezo + bev vs sun was 0.64 and 1.03 for atezo vs sun (table). Tx-related Gr 3-4 AEs were seen in 40%, 16% and 57% of pts in the atezo + bev, atezo and sun arms, respectively. AEs leading to death occurred in 3%, 2% and 2% of pts, respectively. Conclusion: Atezo + bev resulted in encouraging antitumor activity in the PD-L1+ subgroup of first-line RCC pts. Atezo + bev safety is consistent with the known profile of atezo and bev individually. The clinical benefit of atezo + bev vs sun will be evaluated in the ongoing Ph III study IMmotion151 (NCT02420821). Clinical trial information: NCT01984242. [Table: see text]

424 Background: Programmed death-1 (PD-1) receptor negatively regulates T cell-mediated responses.PD-1 ligand (PD-L1) is aberrantly expressed in clear cell renal cell carcinoma (ccRCC) and is associated with worse prognosis. Levels of PD-L1 expressions in non-ccRCC and its association with clinicopathological features and survival are unknown. Methods: Formalin-fixed paraffin-embedded (FFPE) specimens were obtained from 97 patients with chromophobe (CHR), papillary (PAP), translocation Xp11.2 (TrL) RCC and oncoytoma (ONC) and were included in the analysis. PD-L1 expression was evaluated by immunohistochemistry using a mouse monoclonal anti-PD-L1 antibody (405.9A11). The assay was validated using FFPE cell line controls known to be positive or negative for PD-L1 expression by flow cytometry. PD-L1 tumor positivity (PD-L1+) was defined as ≥5% tumor cell membrane staining. For PD-L1 expression in immune cells, a combined score based on the intensity of infiltrate and percentage of positive cells was used. Baseline characteristics including stage/grade, and survival data were collected. Comparisons between PD-L1 expression and clinicopathological features were evaluated using chisq or wilcoxon rank sum tests. Cox model tests for association of PD-L1 expression with OS in univariate and multivariable analysis. Results: Among 97 patients, 12 (12.4%) were considered PD-L1+ in tumor cells: 2/36 (5%) of CHR RCC, 5/50 (10%) of PAP RCC, 3/7 (43%) of TrL RCC, and 2/4 (50%) of ONC. PD-L1 positivity in tumor cells was significantly associated with higher stage (p=0.026) and grade (p=0.046), as well as lower OS on univariate (p=0.02) but not multivariate analysis (p=0.29). On the other hand, PD-L1 positivity by immune cells was observed in 50 (51.5%) patients: 13/36 (36%) of CHR RCC, 30/50 (60%) of PAP RCC, 6/7 (86%) of TrL RCC, and 1/4 (25%) of ONC. PD-L1 positivity in immune cells did not correlate with stage (p=0.7), grade (p=0.1) or OS (p=0.8). Conclusions: PD-L1 expression is variable in non-ccRCC and depends on histology and tumor vs. immune cells scoring. Only PD-L1 positivity in tumors cells was associated with aggressive features. Patients with non-ccRCC should not be automatically excluded from trials of agents that target the PD-1/PD-L1 pathway.

334 Background: Radical cystectomy (RC) represents the standard of care for patients with muscle-invasive urothelial carcinoma of the urinary bladder (UCUB). Alternative organ-conserving treatments such as chemotherapy and/or radiotherapy have gained interest. We sought to compare survival outcomes of patients according to treatment modalities, in a stage-for-stage analysis. Methods: We relied on the Surveillance, Epidemiology, and End Results Medicare-linked database to identify 12,950 patients diagnosed with T2–T4a N0/x M0 UCUB between years 1992 and 2009. Treatment types include RC (n=5207), chemotherapy/radiation (n=2,669), and surveillance (n=5,074). Following instrumental variable analysis, Cox- and competing-risks regression analyses were performed for prediction of overall survival (OS) and cancer-specific mortality (CSM), respectively. All analyses were stratified according to disease stage (T2, T3, T4a). Results: After adjusting for potential confounders, OS was more favorable for RC relative to chemotherapy/radiation (hazard ratio [HR]: 1.57, 95% confidence interval [CI]: 1.02–2.40) or surveillance (HR: 1.82, 95% CI: 1.20–2.78) in patients with T2 UCUB. For the same stage, CSM rates were lower in the surgery group compared to chemotherapy/radiation (HR: 2.05, 95% CI: 1.14–3.67) or surveillance (HR: 1.95, 95% CI: 1.09–3.48). When analyses focused on individuals with more advanced disease (T3–T4a), no statistically significant difference was observed between chemotherapy/radiation relative to RC for both OS and CSM. Conclusions: In the current retrospective population-based cohort, RC was associated with improved survival outcomes relative to its alternative treatment counterparts. However, this effect was only observable in patients with T2 disease. Conversely, no difference between chemotherapy/radiation vs. surgery was noted in patients with more advanced disease stage.

422 Background: There is significant variability in the response to VEGF-TT in mRCC with no validated predictive biomarkers. We hypothesized that whole exome analysis might identify markers of response and resistance to VEGF-TT in mRCC. Methods: mRCC patients who received first-line sunitinib or pazopanib and were in two extreme phenotypes of response were identified. Extreme responders (ER) were defined as PR or CR for ≥3 years (n=10) and primary refractory patients (PRP) were defined as PD within the first 3 months of therapy (n=10). WES was performed in pre-treatment specimens and established Broad Institute analytical pipelines were utilized to identify point mutations and copy number alterations across the exome. ER (n=4) and PRP (n=4) who were part of TCGA project for clear-cell RCC were included in this analysis. Nonsense, missense and indel mutations in established or novel RCC genes were investigated. Results: IMDC prognostic scores were not significantly different between the two groups. VHL mutations were observed at similar frequency in ER and PRP, overall 57%. Mutations in PBRM1 were identified in 7 ER (50%) vs. 1 PRP (7%) (p=0.03). In addition, mutations in TP53 were only found in PRP (p=0.09). No other gene had mutations that were associated with either response or primary refractory disease (Table). Conclusions: In this pilot study, PBRM1 mutations were associated with extreme response to VEGF-TT. However, this was exploratory, and multivariable analysis was not performed. Analysis of additional patient samples is ongoing to confirm or refute this association. If true it suggests that epigenetic effects of PBRM1 mutation may contribute to response to VEGF-TT in mRCC. [Table: see text]

616 Background: Polybromo-1 (PBRM1) and BRCA1 associated protein-1 (BAP1) are genes commonly mutated in clear cell RCC (ccRCC) and have been associated with clinical outcome. This work aims to evaluate the impact of PBRM1 and BAP1 expression by IHC in mRCC patients treated with VEGF-TT. Methods: PBRM1 and BAP1 expression was evaluated by IHC in a TMA including 146 mRCC patients. PBRM1 and BAP1 IHC scores were dichotomized as a binary variable: negative (-) or positive (+) (weak positivity was excluded). The associations of PBRM1 or BAP1 expression with baseline clinico-pathological characteristics were evaluated, as well as with overall survival (OS) and time to treatment failure (TTF) usingCox proportional hazards models. Results: Out of 146 patients, 116 and 109 samples had available results for PBRM1 and BAP1 staining, respectively. Overall, 90% (n = 131) patients had ccRCC. 70/116 samples (60%) were PBRM1- and 26/109 patients (24%) were BAP1-. Only 12% (n = 13) of patients had simultaneous negative PBRM1 and BAP1. While there was no association between PBRM1 expression status and clinical factors, BAP1- samples were associated with poor IMDC prognostic risk score (p = 0.004) and higher Fuhrman grade (p = 0.012). PBRM1+ patients showed a trend towards an increased risk of death and a shorter TTF compared to PBRM1- patients (OS: HR = 1.38, 95%CI: 0.92-2.07, p = 0.1; TTF: HR = 1.39, 95%CI: 0.94-2.06, p = 0.1). BAP1 expression was not independently associated with OS or TTF. Conclusions: Loss of PBRM1, but not BAP1 expression showed a trend towards longer TTF and OS in mRCC patients treated with VEGF-TT.

570 Background: Vascular endothelial growth factor- (VEGF-) and mammalian target of rapamycin- (mTOR-) directed therapies represent a standard of care in metastatic renal cell carcinoma (mRCC). However, these agents are not employed based on an assessment of predictive biomarkers such as genomic alterations (GA). We sought to determine if an association exists between GA detected by comprehensive genomic profiling (CGP) and the response to VEGFR and mTOR pathway targeted therapies in a cohort of mRCC treated in a clinical practice setting. Methods: The results of CGP performed in the course of clinical care on 31 consecutive mRCC obtained from patients who had received VEGFR- and/or mTOR-inhibitors were reviewed. Duration of treatment (DOT), extent and duration of clinical response was obtained from review of medical records. All classes of genomic alterations - base substitutions, short insertions, deletions, gene fusions, rearrangements and copy number - were assessed via CGP. Descriptive statistics were used to determine the frequency of GAs in groups segregated by the DOT with VEGF-directed agents. Results: The most common GAs detected in this series were in VHL (70%), PBRM1 (48%), SETD2 (32%), TSC1 (29%), MLL (19%), TERT (16%), ARID1B (16%) and KDM5C (16%). Across 61 administrations of VEGF-directed therapy in 27 patients, exceptional responses (DOT > 21 months) were more frequent amongst patients with GAs in KDM5C, PBRM1, and VHL. Conversely, these patients also featured a lower frequency of GA associated with response to mTOR-directed therapy, such as TSC1. Conclusions: Multiple GAs are more prevalent in exceptional responders to VEGF-directed therapy. Prospective validation of these findings may lead to use of CGP to optimize therapeutic selection.

501 Background: Reports have demonstrated an inverse relationship between suppression of immune surveillance mechanisms and activation of the vascular endothelial growth factor receptor (VEGFR) pathway suggesting that T cell repertoires may impact response to VEGFR blockade. We evaluated the association between clinical outcomes and T cell repertoire in metastatic RCC patients receiving a front-line anti-VEGFR, pazopanib. Methods: Pre-treatment RCC tumors were analyzed from VEG105192, a phase III study of mRCC patients randomized (2:1) to pazopanib (paz) 800 mg daily vs placebo (pbo) for TCR gamma (TCRG) and TCR beta (TCRB) CDR3 regions. Using the Adaptive Biotechnologies immunoSEQ Assay, we assessed TCR clonality, a measure of total repertoire represented by expanded clones, and entropy, a measure of evenness and diversity. PD-L1 was evaluated by immunohistochemistry (IHC) H-Scores. The goal of the study was to determine if the repertoire of T cell clones was associated with progression-free survival as a clinical endpoint. Results: In the cohort with available tissue, the median PFS was 10.8 and 5.5 months (mos) for paz and pbo, respectively. TCRB (n = 114) and TCRG (n = 43 pbo, 109 paz) clonality ranged from 0-0.31 and 0-0.98, and entropy from 1-12.1 and 0-10.37, respectively. TCRB and TCRG entropy were highly correlated (Spearman’s R = 0.92, n = 114). Samples from the pbo-treated group with higher TCRG entropy, defined as the top 25th percentile, were associated with an improved median PFS (12.8 months) when compared to the lower 75th percentile (3.1 months, P = 0.023); similar trends were seen for TCRB entropy. Neither entropy nor clonality was associated with maximal reduction in tumor volume in the paz-treated group. PD-L1 H-scores were not associated with entropy or clonality (P > 0.05). Conclusions: Our data suggests that RCC samples with higher entropy are associated with a favorable prognosis. Identification of tumors with restricted TCRB/G chain usage and less diverse repertoire, as represented by lower entropy and higher clonality, may impact responses to VEGFR blockade and requires further study. Clinical trial information: NCT00334282.