The effect of post-progression survival on overall survival among patients with sensitive relapse of small cell lung cancer

Recent studies have suggested that, among patients with advanced lung cancer, subsequent treatment after failure of first-line or second-line chemotherapy has a greater effect on overall survival (OS) than tumor shrinkage or progression-free survival (PFS). However, no studies have examined this issue among patients with sensitive relapse of small cell lung cancer (SCLC). We retrospectively evaluate 77 patients with sensitive relapse of SCLC who received second-line chemotherapy after first-line platinum doublet chemotherapy between January 1999 and November 2013. The analyses included patient characteristics, treatment parameters, tumor shrinkage, PFS, post-progression survival (PPS), and OS. Spearman rank correlation analysis and linear regression analysis revealed that PPS was strongly correlated with OS (r = 0.91, p < 0.01, R² = 0.96), PFS was moderately correlated with OS (r = 0.58, p < 0.01, R² = 0.28), and tumor shrinkage was weakly correlated with OS (r = 0.34, p < 0.01, R² = 0.12). A multivariate Cox proportional hazards model with a stepwise regression procedure revealed that PPS was significantly associated with age at the start of second-line chemotherapy, best response to second-line and third-line chemotherapy, and the number of regimens after progression beyond second-line chemotherapy (p < 0.05). These findings suggest that PPS has a stronger effect than PFS on OS among patients with sensitive relapse of SCLC. Thus, response to second-line chemotherapy and subsequent treatment for disease progression after second-line chemotherapy may be important factors that influence OS.