LAUSR

Purpose: In EGFR-mutated metastatic non–small cell lung cancer (NSCLC), outcomes from EGFR tyrosine kinase inhibitors have differed historically by mutation type present, with lower benefit reported in patients with ex21L858R versus ex19del mutations. We investigated if EGFR-activating mutation subtypes impact treatment outcomes in the phase III RELAY study. Associations between EGFR mutation type and preexisting co-occurring and treatment-emergent genetic alterations were also explored. Patients and Methods: Patients with metastatic NSCLC, an EGFR ex19del or ex21L858R mutation, and no central nervous system metastases were randomized (1:1) to erlotinib (150 mg/day) with either ramucirumab (10 mg/kg; RAM+ERL) or placebo (PBO+ERL), every 2 weeks, until RECIST v1.1–defined progression or unacceptable toxicity. The primary endpoint was progression-free survival (PFS). Secondary and exploratory endpoints included overall response rate (ORR), duration of response (DOR), PFS2, time-to-chemotherapy (TTCT), safety, and next-generation sequencing analyses. Results: Patients with ex19del and ex21L858R mutations had similar clinical characteristics and comutational profiles. One-year PFS rates for ex19del patients were 74% for RAM+ERL versus 54% for PBO+ERL; for ex21L858R rates were 70% (RAM+ERL) versus 47% (PBO+ERL). Similar treatment benefits (ORR, DOR, PFS2, and TTCT) were observed in RAM+ERL–treated patients with ex19del and ex21L858R. Baseline TP53 comutation was associated with superior outcomes for RAM+ERL in both ex19del and ex21L858R subgroups. EGFR T790M mutation rate at progression was similar between treatment arms and by mutation type. Conclusions: RAM+ERL provided significant clinical benefit for both EGFR ex19del and ex21L858R NSCLC, supporting this regimen as suitable for patients with either of these EGFR mutation types.