Diverse RB1 mutations and co-occurring molecular alterations in advanced NSCLC.

Abstract

e20672 Background: Retinoblastoma transcriptional corepressor 1 (RB1) mutation is strikingly more frequent in non-small cell lung cancer (NSCLC) with SCLC transformation (SCLC-T) than that remain NSCLC. However, NSCLC patients harboring RB1 mutations do not necessarily transform to SCLC. Thus, exploring RB1 mutation frequency and co-occurring genomic alterations is potentially important to understand the SCLC-T mechanism. Methods: We investigated 47 NSCLC pts with RB1 aberrations at our institution. Submitted samples (tissue, plasma, cerebrospinal fluid and pleural effusion) were analyzed using next-generation sequencing across at least 139 genes (139-520). Demographics, molecular features and outcomes were analyzed. Results: Among 47 pts (27F/20M), median age was 58. Twenty (47%) had brain metastases and 7 (15%) underwent SCLC-T. A total of 39 types of RB1 mutations were identified, in which copy number deletion is the most common (40%). RB1 mutations were present from early NSCLC and were detected in 88%(29/33), 82%(9/11), 70%(9/13) and 42% (20/48) of tissue, pleural effusion, CSF and plasma samples, respectively. The most frequent co-occurring alterations were TP53 (100%, 95%) and EGFR (100%, 93%) in both SCLC-T group and non-transformed group. Besides, mutations involving in the PI3K pathway were often detected: PIK3CA (57%, 20%), AKT (43%, 10%), PTEN (14%, 15%), MET (14%, 15%), NTRK1 (14%, 13%). Notably, RB1 also co-occurred with ALK fusion (1/47). Moreover, SCLC-T group harbored significant higher frequency of RB1 mutation compared with non-transformed group. Conclusions: RB1 mutations in NSCLC are associated with a trend toward SCLC-T, and the mechanisms may be increased frequency of RB1 mutations and co-occurring similar molecular alterations to those in SCLC.