Chemotherapy-induced neutropenia as a prognostic factor in patients with extensive-stage small cell lung cancer

Purpose Chemotherapy-induced neutropenia (CIN) is a dose-limiting factor for cytotoxic chemotherapy, but recently, it was suggested that CIN contributes to prolonged survival. In this study, we examined the association between severe CIN and survival and determined whether CIN affected survival in patients with extensive-stage small cell lung cancer (ES-SCLC). Methods The medical records from 214 patients with ES-SCLC treated with etoposide or irinotecan in combination with cisplatin (EP/IP) between 2012 and 2016 were collected and retrospectively analyzed. Landmark analysis was performed at the end of cycle 4, and the relationship between severe CIN and survival was determined by a log-rank test. In addition, a multivariate analysis using the COX proportional hazard model was performed to identify independent predictive factors. The Landmark analysis included 102 patients in the IP group and 47 patients in the EP group. Results No significant difference was found between grades 0–3 and grade 4 neutropenia and overall survival (OS) in the EP group ( P = 0.57). Contrariwise, for the IP patients, the median OS was 444 days for grades 0–3 and 633 days for grade 4 neutropenia, which was significantly longer for patients who developed grade 4 neutropenia ( P = 0.03). Multivariate analysis adjusted for potential factors revealed that the development of grade 4 CIN was identified as a significant predictor of longer OS (hazard ratio [HR], 0.50; 95% confidence interval (CI), 0.28–0.87, P = 0.015). Conclusion The results indicated that the development of severe CIN with IP therapy is associated with prolonged OS.