Impact of the presence of EGFR mutation on definitive chemoradiotherapy in patients with locally advanced non-small cell lung cancer: Pattern of relapses and survival analyses in 145 patients.

7540 Background: EGFR mutational status is an important biomarker in advanced NSCLC patients. However, little is known about the frequency and clinical significance of the presence of EGFR mutation in patients with potentially curable locally advanced NSCLC (LA-NSCLC) eligible for definitive chemoradiotherapy (CRT). Methods: Between Jan 2001 and Dec 2010, we conducted analysis for the presence of EGFR mutations, in consecutive NSCLC patients who were eligible for CRT. The response rate (RR), progression-free survival (PFS), 2-year relapse-free rate, first relapse sites, and overall survival were investigated according to the EGFR mutational status. Results: A total of 528 patients received CRT at the National Cancer Center Hospital during the study period. Of these, 274 were diagnosed as having non-squamous NSCLC, and sufficient specimens for mutational analyses could be obtained from 145 patients. EGFR mutants (EGFR-mt) were found at a frequency of 18% in these patients. In addition to the well-known characteristics of NSCLC patients carrying EGFR mutations (female, adenocarcinoma, and never/ light smoker), the proportion of cases with smaller (T1/2) primary lesions was higher in patients with EGFR-mt than in those carrying wild-type EGFR (EGFR-wt). EGFR-mt showed a slightly better RR (85.7% vs. 72.9%), but similar median PFS (12.2 m vs. 10.6 m) and 2-year relapse free rates (23.8% vs. 29.2%) as compared to EGFR-wt. Local recurrence as first relapse occurred less frequently in EGFR-mt than in EGFR-wt (6% vs. 20%). After disease progression, a majority of EGFR-mt received EGFR-TKIs (62%), and these patients showed longer post-progression survival and a higher 5 year survival rate (60% vs. 40%) than EGFR-wt. Conclusions: Among the LA-NSCLC patients eligible for definitive CRT analyzed, 18% had EGFR- activating mutations. Although definitive CRT was similarly effective in both EGFR-mt and EGFR-wt, slightly better local control rate was noted in EGFR-mt. Treatment with EGFR-TKIs contributed to longer post-progression survival and overall survival in LA-NSCLC patients harboring EGFR mutations.