Differential progression-free survival (PFS) to erlotinib according to EGFR exon 19 deletion type in non-small cell lung cancer (NSCLC) patients (p) in the EURTAC study.

Abstract

7540 Background: Different exon 19 deletion types have shown different in vitro sensitivity to erlotinib, with the lower IC50 for deletion E746_A750 (ELREA) (Yuza et al. Cancer Biol Ther 2007). This information prompted us to examine outcome according to type of exon 19 deletion in the EURTAC study. Methods: The EURTAC trial (clinicaltrials.gov NCT00446225) randomized 174 p with EGFR exon 19 deletions or L858R mutations to receive erlotinib or chemotherapy. Progression-free survival (PFS) was 9.7 months (m) vs 5.2 m, respectively (P<0.0001). Exon 19 deletions were divided into two groups: ELREA vs non-ELREA deletions. Results: Exon 19 deletions were present in 57 p in the erlotinib arm and in 58 p in the chemotherapy arm. ELREA deletions were found in 41 p (71.9%) in the erlotinib arm and in 38 p (65.5%) in the chemotherapy arm. Non-ELREA deletions were found in 16 p in the erlotinib arm and in 20 p in the chemotherapy arm. There were no differences in p characteristics between treatment arms according to type of deletion. PFS for p with ELREA deletions was 9.4 m in the erlotinib arm and 4.6 in the chemotherapy arm (HR, 0.36; P=0.0004). PFS for p with non-ELREA deletions was not reached in p in the erlotinib arm and was 5.3 m for p in the chemotherapy arm (HR, 0.17; P=0.001). The multivariate analysis identified erlotinib arm (P<0.001) and non-ELREA deletions (P=0.001) as independent markers of longer PFS. Overall survival (OS) for p with ELREA deletions was 17 m in the erlotinib arm and 18.4 in the chemotherapy arm (P=0.575). OS for p with non-ELREA deletions was not reached in the erlotinib arm and 19.5 m in the chemotherapy arm (P=0.216). Response rate (RR) for p with ELREA deletions was 53.6% in the erlotinib arm vs 15.7% in the chemotherapy arm (P=0.004). RR for p with non-ELREA deletions was 68.7% in the erlotinib arm vs 10% in the chemotherapy arm (P=0.001). Conclusions: To date, no biological reason has been identified that can explain the greater sensitivity to erlotinib in p with non-ELREA exon 19 deletions. Our findings indicate the need to define the type of deletion prior to treatment since this information can be helpful in predicting the duration of response.