1259P - Differential efficacy of cisplatin plus pemetrexed between L858R and Del-19 in advanced EGFR-mutant non-squamous non-small cell lung cancer

Abstract

LUX-Lung 3 showed afatinib improved progression-free survival (PFS) compared with cisplatin plus pemetrexed in patients with epidermal growth factor receptor (EGFR) mutations. In this study, chemotherapy efficacy tended to differ between patients with Leu858Arg (L858R) point mutation and Exon 19 deletion (Del-19); PFS in L858R patients (8.1 months) was greater than in Del-19 patients (5.6 months). We investigated whether there is any difference in efficacy of cisplatin plus pemetrexed between Del-19 and L858R. This study is a multicenter retrospective study. We reviewed medical records of patients who had received cisplatin plus pemetrexed as first line chemotherapy. Efficacies were evaluated between EGFR mutation status: Del-19 and L858R. Wild type cases were reference arm only, and not included in any statistical analysis. Among 304 patients, 78 (25.7%) harbored EGFR mutations: Del-19 (36/78 patients, 46.2%); and L858R (42/78, 53.8%). Median PFS of L858R group (9.4 months, 95% confidence interval [CI]: 7.0–12.6) was significantly longer than Del-19 group (5.5 months, 95% CI, 3.6–8.6) (p = 0.049). Response rate (RR) and OS presented no significant difference between L858R and Del-19. In multivariate analysis, EGFR mutation status (L858R versus Del-19) was the only significant factor for longer PFS (Hazard ratio [HR]: 0.78, 95% CI: 0.62–0.98) (p = 0.033). Our study indicated better efficacy of cisplatin plus pemetrexed in L858R than in Del-19 patients. In EGFR-mutant NSCLC, EGFR-TKIs are undoubtedly the premier therapy. However, in second line or later settings, cisplatin plus pemetrexed regimen may confer higher efficacy for L858R patients.