The depth of response was associated with the progression-free survival in advanced non-small cell lung cancer patients treated with EGFR-TKI.

Abstract

e20509 Background: Response Evaluation Criteria in Solid Tumors (RECIST) has been widely utilized to evaluate the new therapeutic strategies in cancer, however, RECIST fails to differentiate the heterogeneity of response in highly active therapies. Depth of response (DepOR), defined as maximum percent change in tumor size compared with baseline, may provide a new strategy to evaluate disease response. In the present study, we studied the association between DepOR and progression-free survival (PFS) in patients with advanced non-small cell lung cancer (NSCLC) treated with epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI). Methods: Advanced NSCLC patients harboring EGFR driver mutation (L858R or 19del) treated with EGFR-TKI from August 2014 to July 2017 in two sites were retrospetively collected for analysis. Patients were divided into four groups by maximal tumor shrinkage (Q1 = 1-25%, Q2 = 26-50%, Q3 = 51-75%, Q4 = 76-100%). Kaplan-Meier curves were plotted for PFS by DepOR and the hazard ratio (HR) was determined through univariable and multivariable Cox regression models. Results: In total, 265 patients were included for analysis. The number for Group Q1-Q4 was 91, 73, 65 and 36, respectively. The greater DepOR was significantly associated with a longer PFS (Log-rank P for trend < 0.0001). The DepOR vs PFS analyses HR were 0.58 (0.42-0.80) for Q2, 0.49 (0.35-0.69) for Q3 and 0.33 (0.22-0.50) for Q4 compared with Q1. In the multivariable cox regression model, abnormal LDH, brain metastasis and male were also found to be associated with poorer PFS (P < 0.05). Conclusions: Greater DepOR was significantly associated with a longer PFS in advanced NSCLC treated with EGFR-TKI, suggesting that it may be a useful clinical outcome to more efficiently evaluate the response of targeted therapy.