Response to Standard Therapies and Comprehensive Genomic Analysis for Patients with Lung Adenocarcinoma with EGFR Exon 20 Insertions.

PURPOSE: EGFR exon 20 insertions (ex20ins) are an uncommon genotype in non-small cell lung cancer (NSCLC) for which targeted therapies are under development. We sought to describe treatment outcomes and genomic and immunophenotypic characteristics of these tumors. EXPERIMENTAL
DESIGN: We identified sequential patients with NSCLC with EGFR ex20ins and compared their clinical outcomes and pathologic features with other patients with NSCLC.
RESULTS: Among 6,290 patients with NSCLC, 106 (2%) had EGFR ex20ins. Patients with EGFR ex20ins were more likely to be Black (14% vs. 6%; P < 0.001) or Asian (22% vs. 10%; P < 0.001) compared with all other patients with NSCLC. Median tumor mutational burden (TMB; 3.5 vs. 5.9; P < 0.001) and proportion of tumors with PD-L1 expression ≥1% (22% vs. 60%; P < 0.001) were lower in EGFR ex20ins compared with other NSCLCs (TMB, n = 5,851 and PD-L1 expression, n = 282) and EGFR del 19/L858R (median TMB, 3.5; P = 0.001 and 39% PD-L1 ≥ 1%; P = 0.02). Compared with a 2:1 cohort of patients with metastatic NSCLC without targetable alterations (n = 192), EGFR ex20ins patients had longer overall survival (median 20 vs. 12 months; HR, 0.56; P = 0.007) and longer time to treatment discontinuation (TTD) for platinum chemotherapy (median, 7 vs. 4 months; HR, 0.6; P = 0.02) and no improvement in TTD for immune checkpoint inhibitors (ICI; HR, 1.75; P = 0.05).
CONCLUSIONS: With better outcomes on platinum chemotherapy, patients with EGFR ex20ins NSCLC have improved prognosis, lower PD-L1 expression and TMB, and derive less benefit from ICIs compared with patients with NSCLC without targetable oncogenes. Improving molecularly targeted therapies could provide greater benefit for patients with EGFR ex20ins. ©2021 American Association for Cancer Research.