The impact of EGFR subtype combined with TP53 co-mutation status on survival outcomes with front-line osimertinib in non-small cell lung cancer (NSCLC).
BACKGROUND: Osimertinib is a standard therapy for EGFR-mutant NSCLC. However, markers to better identify those at risk for poor outcomes are needed. This is the largest study to date evaluating the impact of EGFR subtype combined with TP53 co-mutation status on survival endpoints with front-line osimertinib. METHODS: Patients from a U.S. clinical-genomic database with advanced EGFR-mutant NSCLC receiving front-line osimertinib were studied. Real-world progression-free survival (rwPFS) and overall survival (OS) were determined using Kaplan-Meier methods, and multivariable Cox regression compared outcomes after accounting for relevant clinical covariates. RESULTS: Of 606 patients, 277 (46%) had EGFR L858R, 384 (63%) had TP53 co-mutations, and 186 (30.7%) had both. Bearing L858R vs. exon 19 deletions (rwPFS: hazard ratio [HR] 1.4, P = 0.001; OS: HR 1.3, P = 0.01) or a TP53 co-mutation vs. wildtype (rwPFS: HR 1.5, P < 0.001; OS: HR 1.6, P < 0.001) predicted inferior outcomes. Especially short median rwPFS (10.1 vs. 21.4 months, HR 2.2, P < 0.001) and OS (21.3 vs. 53.4 months, HR 2.3, P < 0.001) were observed in patients with both markers (L858R/TP53-mutant) as compared to neither (exon 19 deletion/TP53-wildtype). CONCLUSIONS: Having EGFR L858R or a TP53 co-mutation were independent predictors of inferior rwPFS and OS with front-line osimertinib. Patients with both unfavorable alterations had the shortest survival. Risk stratifying using a combination of these markers can assist in identifying patients for novel trials or approved intensified therapies.