Clinical impact of post‐progression survival on overall survival in elderly patients with extensive disease small‐cell lung cancer

BACKGROUND The effects of first-line chemotherapy on overall survival (OS) might be confounded by subsequent therapies in patients with small-cell lung cancer (SCLC). Therefore, the objective of our study was to determine the relationships between progression-free survival (PFS) or post-progression survival (PPS) and OS after first-line chemotherapy in elderly patients with extensive disease-SCLC (ED-SCLC), using individual level data. METHODS Between July 1998 and December 2014, we analyzed 57 cases of elderly patients with ED-SCLC who were treated with carboplatin and etoposide as first-line chemotherapy. The relationships between PFS and PPS with OS were analyzed at an individual level. RESULTS Spearman rank correlation and linear regression analyses showed that PPS was strongly correlated with OS (r = 0.92, P < 0.05, R 2  = 0.83) and PFS was moderately correlated with OS (r = 0.76, P < 0.05, R 2  = 0.25). The best response at second-line treatment and the number of regimens after progression beyond first-line chemotherapy were both significantly associated with PPS (P < 0.05). CONCLUSIONS PPS has a stronger impact on OS than PFS in elderly ED-SCLC patients after first-line chemotherapy. In addition, the response at second-line treatment and the number of additional regimens after first-line treatment are significant independent prognostic factors for PPS. These results suggest that OS in elderly ED-SCLC patients may be influenced by treatments subsequent to first-line chemotherapy; however, this remains to be verified with prospective studies.