7034 Background: Mutations in the epidermal growth factor receptor (EGFR) are associated with response to chemotherapy in patients with advance NSCLC. The purpose of this study was to assess the association of mutations in the EGFR tyrosine kinase domain and the efficacy of adjuvant chemotherapy in patients with fully resected IIIA-N2 NSCLC tumors. Methods: Tumor samples (n =150) from patients in our prior trial with IIIA-N2 NSCLC who either had or had not received paclitaxel/vinorelbine plus carboplatin chemotherapy following removal of the tumor were analyzed for EGFR mutations in exons 19 and 21. The association of the presence of EGFR mutations and survival following treatment was assessed. Results: Mutations were identified in 33 (22%) patients (n=13 in the no chemotherapy [observation] arm and n=20 in the chemotherapy arm). Fourteen patients (9.3%) had deletion mutations in exon 19, and 19 patients (12.7%) had a substitution mutation in exon 21. Compared with patients wild-type for EGFR, patients with EGFR mutations had numerical but not statistically significant improved disease-free survival (35 months [95% CI, 14.6-55.4] versus 23 months [95% CI, 17.3-28.7], respectively, P=0.339) and overall survival (36 months [95% CI, 27.9 to 44.1] versus 26 months [95% CI, 20.1 to 31.9], respectively p=0.271) regardless of treatment. Patients with wild-type EGFR had greater overall survival with chemotherapy compared to no adjuvant therapy (HR=1.920; 95%CI, 1.245-2.963; p=0.003). In contrast, EGFR mutant patients in the observation group compared to the chemotherapy group had longer median disease-free survival (35 months [95% CI, 20.9 to 49.1] versus 27 months [95% CI, 5.3 to 48.7], respectively, p=0.671) and overall survival (33 months [95% CI, 24.2 to 41.8] versus 40 months [95% CI, 31.8 to 48.2] respectively, p =0.360). Conclusions: In this study, the status of mutations in exons 19 and 21 of EGFR was associated with different clinical outcomes in patients with resected IIIA-N2 NSCLC tumors either treated with or without adjuvant chemotherapy. These findings suggest that a patient’s treatment should be customized to their EGFR mutational status.