MA14.10 Clinical Outcomes in Metastatic Squamous Lung Cancer with Targetable Driver Alterations

Abstract

Genomic profiling is not routinely performed for metastatic squamous (SCC) and adenosquamous (ASC) NSCLC. However molecular profiling may be ordered if demographic features suggest a higher likelihood of a targetable driver alteration (e.g. never or remote smoking history). Response and survival data are scant in pts with actionable alterations treated with targeted therapy. We reviewed the clinical data and molecular profiling (FISH, PCR, tissue NGS, ctDNA) of metastatic SCC and ASC pts treated at our institution from Feb 2010-Dec 2018. Pts with typical sensitizing mutations in EGFR or BRAF V600E or fusions in ALK or ROS1 treated with matched targeted therapy for ≥2 months were included in this analysis. Response assessment was based on RECIST v1.1. Among 261 metastatic SCC or ASC pts with available molecular profiling, 16 total pts (6%) were found to have actionable targets, consisting of 13 SCC and 2 ASC (median age 53, 81% female, 88% never-smoker). The distribution of driver alterations in this cohort was 56% (9/16) EGFR ex19del/L858R/G719A, 38% (6/16) ALK fusion, and 6% (1/16) BRAF. The overall objective response rate (ORR) and median progression free survival (PFS) to targeted therapy was 69% and 5.2 months respectively. By mutational subgroup, ORR was 67% (6/9) for EGFR, 67% (4/6) for ALK, and 100% (1/1) for BRAF. Median PFS was only 4.5 months (95% CI 3.0 – 6.0) for EGFR pts and 2.8 months (95% CI 0 – 6.4) for ALK pts, and the lone BRAF pt had a PFS of 8.5 months. In EGFR pts with available NGS, co-mutations in TP53 (75% [6/8]) and PIK3CA (38% [3/8]) were seen at rates higher than previously reported in EGFR+ ADC (TP53 55%, PIK3CA 12%; Blakely et al, Nat Gen 2017). In ALK pts with available NGS, co-mutations in TP53 (80% [4/5]) were also higher than recently reported in ALK+ ADC (24%; Kron et al, Ann Oncol 2018). Despite initial responses comparable to those previously reported in ADC, matched targeted therapy in pts with SCC and ASC histology is associated with shorter PFS. A higher prevalence of adverse co-mutations such as TP53 and PIK3CA may contribute to early targeted therapy resistance in these histologies. These findings may have implications for the use of targeted therapy in squamous lung cancer.