NF2 mutation-driven renal cell carcinomas (RCC): A comprehensive genomic profiling (CGP) study.

Abstract

726 Background: NF2 genomic alterations (GA) have been associated with aggressive behavior in RCC. Methods: FFPE tissues from 1,386 clear cell (ccRCC), 307 papillary (pRCC), 72 chromophobe (chRCC), 145 sarcomatoid (sRCC), 54 collecting duct (cdRCC),37 medullary (medRCC) and 134 unclassified (nosRCC) underwent hybrid-capture based CGP to evaluate all classes of genomic alterations (GA). Tumor mutational burden (TMB) was determined on up to 1.1 Mbp of sequenced DNA and MSI was determined on 114 loci. PD-L1 expression was determined by IHC (Dako 22C3). Results: 140 (7%) RCC featured NF2 GA which were predominantly short variant (SV) mutations. Gender and age were similar with male preponderance in all histologic subtypes. NF2 GA frequency was highest in cdRCC (20%) and sRCC (19%) and lowest in ccRCC (3%). The medRCC at 5% NF2 GA and chRCC at 0% NF2 GA were not further evaluated. VHL and PBRM1 GA were significantly more frequent in NF2 altered ccRCC than all other RCC (P < 0.001). Other mTOR pathway GA were uncommon. Potentially targetable kinase GA in NF2-mutated RCC included BRAF (2% of ccRCC), EGFR (3% of pRCC), ERBB3 (4% of sRCC) and PIK3CA (9% of cdRCC). No NF2 mutated RCC featured MSI -high status and both TMB and PD-L1 expression levels were extremely low in all subsets with exception of high PD-L1 staining in sRCC tumors. Conclusions: cdRCC, sRCC, pRCC and nosRCC are enriched in NF2 GA. Low PBRM1 GA, TMB and MSI- high predict resistance to immunotherapy in NF2 mutated RCC although the high PD-L1 expression in sRCC is noteworthy.[Table: see text]