A Randomized Phase 2 Study of Gefitinib With or Without Pemetrexed as First-line Treatment in Nonsquamous NSCLC With EGFR Mutation: Final Overall Survival and Biomarker Analysis

Introduction: Clinical studies have shown that a combination of a tyrosine kinase inhibitor (TKI) and pemetrexed overcame acquired resistance to epidermal growth factor receptor (EGFR) TKI in NSCLC. Previously, pemetrexed+gefintib (P+G) had improved progression-free survival (PFS) compared with gefitinib. We present OS, updated PFS, biomarker analysis, and safety of P+G versus gefitinib.

Methods: This was a phase 2, multicenter, randomized study conducted in East Asian patients with advanced nonsquamous NSCLC with EGFR mutations. Patients were randomized (2:1) to receive P+G (500 mg/m² intravenously 3-weekly + 250 mg/day orally) or gefitinib.

Results: In total, 191 patients (P+G, n=126; gefitinib, n=65) comprised the intent-to-treat and safety populations. Median OS was 43.4 months in P+G versus 36.8 months in gefitinib arm; adjusted HR 0.77 (95% CI, 0.5-1.2); one-sided P=0.105. Median PFS was significantly longer in the P+G (16.2 months) versus gefitinib arm (11.1 months); adjusted HR 0.67 (95% CI, 0.5-0.9); one-sided P=0.009. In the P+G and gefitinib arms, median PFS was 22.6 and 11.0 months, respectively, in patients with low thymidylate synthase (TS) expression, and 12.6 and 9.9 months, respectively, in patients with high TS expression. Common second-line post-discontinuation systemic therapies were EGFR-TKIs and chemotherapy. Most patients experienced at least one adverse event.

Conclusions: Addition of pemetrexed to EGFR TKI gefitinib resulted in significantly improved PFS and numerically longer OS compared with gefitinib in treatment-naïve patients with EGFR-mutated advanced nonsquamous NSCLC. Low TS expression appeared to be a good predictor for treatment outcomes.