Résumé
Abstract only 10507 Background: The EGFR exon 19 deletion and exon 21 L858R mutation are associated with response to EGFR-TKI. However, the correlation with response to EGFR-TKI remains unclear for rare exon 18 and 20 EGFR mutations. We investigated the clinical features of NSCLC patients with exon 18 and exon 20 EGFR mutations, analyzed response to EGFR-TKI and patient's survival. Methods: Between 2005 and 2011, all rare exon 18 and 20 EGFR mutations were collected from 10117 cases of NSCLC in 15 of 28 French NCI molecular genetic laboratories. Results: During the study period, EGFR mutations were identified in 1048 (10.35%) out of the 10117 performed tests and 108 rare mutations (10.3%) were identified in 103 patients, including 25 never identified mutations. Among them, 48 mutations were localized at exon 18 and 60 at exon 20, with 3 out of the 4 identified T790M exon 20 mutations associated with L858R mutation. Only 5 other rare mutations were associated with EGFR 19 or 21 mutations. 38 patients received EGFR-TKI (erlotinib, n=32; gefitinib, n=6). Among the 36 evaluable patients, best response on TKI was progression in 18 patients (50%), stabilization in 11 (30.5%) and partial response in 7 (19.4%). Tumor control rate observed in exon 18 mutations was 61% (8/13) and 50% (13/26) in exon 20 mutations. For the EGFR-TKI treated patients, the median PFS was 6 months (2-53). Median OS was 15 months (1-92), with no difference between the EGFR-TKI treated patients or not. Conclusions: Prevalence of rare EGFR mutations was 1.06% of all tested NSCLC and 10.35% of all EGFR mutations. Tumor control on TKI was observed in half of the patients. Reports of NSCLC harboring rare mutations are important to help the decision-making process in this subset of patients.