Early radiological response as predictor of overall survival in non-small cell lung cancer (NSCLC) patients with epidermal growth factor receptor mutations.

Background: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) are the standard treatment of advanced, EGFR -mutant non-small-cell lung cancer (NSCLC). Usually, radiographic assessment of response to chemotherapy is performed after the patient completes the second course of treatment. The optimal timing of response evaluation for patients receiving EGFR-TKIs is, however, not well-defined. The purpose of this study is to evaluate the association of an early radiological response (ERR) to TKIs by computed tomography (CT) with progression-free survival (PFS) and overall survival (OS) in advanced NSCLC patients with EGFR mutations.

Methods: EGFR mutation status was analyzed retrospectively in a cohort of 360 NSCLC patients' between January 2009 and November 2014. Forty of them received treatment with TKI and therefore were included in the study. Response to TKI therapy was defined according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. ERR was defined as complete response (CR) or partial response (PR) at the first radiographic evaluation performed within 6-8 weeks after the beginning of the treatment.

Results: Activating mutations in the tyrosine kinase domain of the EGFR gene were mainly exon 19 deletions. Thirty patients (75%) had ERR, 4 of those patients (10%) showed a PR on early CT achieving a CR in the long-term monitoring. Median PFS was longer in patients experiencing an ERR (10.9 vs. 2.4 months; HR: 0.42; 95% CI: 0.19-0.93; P=0.033) than those that did not [stable disease (SD) or progressive disease (PD)]. Median overall survival OS was also significantly increased in patients experiencing ERR (23.2 vs. 11.9 months; HR: 0.3; 95% CI: 0.15-0.85; P=0.021).

Conclusions: ERR in patients treated with EGFR TKI therapy is associated with statistically significant PFS and OS, and could be a surrogate marker of efficacy in these patients. Moreover, ERR provides an early identification of patients not benefitting from TKI, despite the presence of activating EGFR mutations in which further efforts are needed to improve their prognosis.