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

• Published in: Journal of clinical oncology Vol. 37; no. 7_suppl; p. 666
• Main Authors: Hakimi, A. Ari, Ged, Yasser, Flynn, Jessica, Hoen, Douglas R, Di Natale, Renzo G, Blum, Kyle A, Makarov, Vladimir, Kuo, Fengshen, Carlo, Maria Isabel, Lee, Chung-Han, Voss, Martin Henner, Ostrovnaya, Irina, Chan, Timothy An-thy, Motzer, Robert J.
• Format: Journal Article
• Language: English
• Published: 01.03.2019
• ISSN: 0732-183X; 1527-7755
• DOI: 10.1200/JCO.2019.37.7_suppl.666

Abstract only 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]