Comparison of cisplatin-versus carboplatin-based concurrent chemoradiation for limited-stage small cell lung cancer using SEER-Medicare data

Background: Small cell lung cancer (SCLC) accounts for 14% of lung cancers. Current standard therapy for limited stage (AJCC stages I-III) SCLC is concurrent chemoradiation (CCRT) with cisplatin/etoposide but carboplatin/etoposide is often used for patients with poor tolerance or contraindication to cisplatin. The aim of this retrospective cohort study is to compare survival of cisplatin (cis) and carboplatin (carb) based CCRT in limited stage SCLC. Methods: Cases were selected from the population-based SEER-Medicare lung cancer database if the patient's first cancer was limited stage SCLC diagnosed at age 66-80 in 1992-2007. CCRT was defined with radiation starting within 60 days of the start of the first cycle of cis/carb. Study endpoints were overall survival (OS, time from diagnosis until death) and cause specific survival (CSS, time from diagnosis until death from lung cancer). SAS v9.3 was used to select cases, and R v3.0.2 was used to calculate Kaplan-Meier survival analysis and log-rank tests for significance. Results: Study sample meeting inclusion criteria included 1603 patients, with median age 72 (66-81) and gender ratio 1.1. Majority were stage III (n=1342, 84%), with some stage I (11%) and II (5%). Cis was used in 617 cases (38%) while carb was used in 986 cases (62%). On average, cis group was younger (p<0.001). Median (OS, CSS) were (1.20, 1.34) and (1.17, 1.33) years for cis and carb groups, respectively. Five-year (OS, CSS) for cis and carb were (13.7%, 24.4%) and (11.1%, 20.5%), respectively. There was no statistically significant difference in OS (p=0.163) or CSS (p=0.683) between the groups. Conclusions: Cis vs carb based CCRT had comparable OS and CSS, even though cis group was younger. This suggests that if carb is better tolerated, it should be preferred for limited stage SCLC, though randomized trials are needed.