Abstract C136: VHL, PBRM1, and BAP1 mutation variants and response to first-line therapies in patients with metastatic clear-cell renal cell carcinoma (mRCC)
Authors: Zhu Jessica , Hu Junxiao , Lam Elaine T 
Published: December 2023

Abstract
Background VHL, PBRM1, and BAP1 are common mutations in clear-cell renal cell carcinoma (ccRCC). VHL and PBRM1 mutations result in downstream dysregulation of vascular endothelial growth factor receptor (VEGFR) that cause angiogenesis and uncontrolled cell growth. VEGFR tyrosine kinase inhibitors (TKI) are the mainstay of ccRCC treatment. The current first-line (1L) therapies for mRCC include combination anti-VEGFR TKI + anti-PD-1 immune checkpoint inhibitors (CPI), or combination CPI targeting PD-1 and CTLA-4. It is unknown whether VHL and PBRM1 mutations are predictive for response to 1L anti-VEGFR TKI, anti-VEGFR TKI + CPI, or combination CPI immunotherapy. In this retrospective observational study, we evaluated the real-world outcomes of 1L therapies in patients with mRCC with or without VHL, PBRM1, or BAP1 mutations.
Methods This study used the nationwide de-identified Flatiron Health-Foundation Medicine RCC clinico-genomic database, originating from approximately 280 cancer clinics (~800 sites of care). Patients with metastatic ccRCC, diagnosed from 8/1996-8/2022, who received 1L therapy with anti-VEGFR TKI, anti-VEGFR TKI + PD-1/PD-L1, or anti-PD-1 + anti-CTLA-4 therapy, and who had comprehensive genomic profiling were included. The primary endpoint was real-world overall survival (rwOS) in mRCC patients with VHL mutations. Secondary endpoints included rwOS and real-world progression-free survival (rwPFS) in patients with BAP1 and PBRM1 mutations, and rwPFS in patients with VHL mutations. The cox proportional hazard model was used to conduct the multivariable analysis adjusting for demographic/clinical factors for rwOS and rwPFS. The Kaplan-Meier method were used to estimate the median survival time.
Results149 patients with complete data sets were included, of whom 99 had VHL mutations, 65 had PBRM1 mutations, and 31 had BAP1 mutations. Eight patients (5%) had favorable International Metastatic RCC Database Consortium (IMDC) risk, 110 (74%) had intermediate IMDC risk, and 31 (21%) had poor IMDC risk. The adjusted hazard ratio (HR) for rwOS in patients with VHL mutations compared to those without who received 1L anti-VEGFR TKI, anti-VEGFR TKI + PD-1/PD-L1, or PD-1/PD-L1 + CTLA-4 therapy were 1.53 (95% CI: 0.78-3.00, p=0.221), 0.87 (95% CI: 0.29-2.61, p=0.798), and 1.64 (95% CI: 0.71-3.75,p=0.245), respectively. The median rwOS for patients with PBRM1 mutations who received anti-VEGFR TKI was 50.1 months (95% CI: 34.62-NR) and 30.6 months (95% CI: 19.4-63.2) in patients without PBRM1 mutations (adjusted HR 0.54, 95% CI: 0.29-1.00, p=0.049). The median rwPFS for BAP1 mutations with anti-VEGFR TKI therapy was 5.2 months (95% CI: 3.6-9.1) and 6.4 (95% CI: 4.7-10.8) in patients without BAP1 mutations (adjusted HR 2.45, 95% CI: 1.35-4.44, p=0.003).
Conclusion No significant difference was observed in rwOS in mRCC patients with VHL mutations treated with first-line anti-VEGFR TKI, anti-VEGFR TKI + PD-1/PD-L1, or PD-1/PD-L1 + CTLA-4 therapy, compared to patients without VHL mutations. Additional studies are needed to confirm this finding.
Citation Format: Jessica Zhu, Junxiao Hu, Elaine T Lam. VHL, PBRM1, and BAP1 mutation variants and response to first-line therapies in patients with metastatic clear-cell renal cell carcinoma (mRCC) [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C136.