Evaluation of postoperative radiotherapy in limited-stage small cell lung cancer with propensity score matching analysis

Abstract:

Objective：To investigate the role of postoperative radiotherapy（PORT） in resected limited-stage small cell lung cancer（SCLC）. Methods：The clinical data of 915 patients with limited-stage SCLC from the SEER（surveillance，epidemiology，and end results） database who received surgical treatment in 2000-2016 were retrospectively analyzed. Propensity score matching（PSM） method was used to balance the covariate bias between PORT（+） and PORT（-） groups. The survival curves were drawn by Kaplan-Meier method，and log-rank test was used to check survival difference of two groups. Overall survival（OS） and lung cancer specific survival（LCSS） were compared between these two patient groups，and the role of postoperative radiotherapy and the subgroups that benefited from postoperative radiotherapy were analyzed. Results：The median OS and LCSS were 31 months and 37 months respectively. There was no significant difference in OS and LCSS between PORT（+） and PORT（-） groups before and after the propensity score matching. When analyzed by subgroup，no differences in OS and LCSS were observed in patients with all N stages（N0，median OS：61 months vs. 62 months；P=0.838；N1，median OS：22 months vs. 20 months；P=0.735；N2，median OS：19 months vs. 16 months；P=0.254）. Patients whose lymph node ratio（LNR） was greater than 50% had significantly improved OS（HR=0.57，95%CI=0.35-0.93；P=0.024） and LCSS（HR=0.57，95%CI=0.34-0.95；P=0.030）with PORT. Multivariate analysis showed that age，type of surgery，LNR，T stage and N stage were independent prognostic factors in patients with resected limited-stage SCLC. Conclusion：The use of PORT has no relationship with the survival of N0，N1 and N2 patients. The survival benefit associated with PORT in this disease seems to be limited to those with LNR of 50% or more. This needs to be further evaluated in other similar studies and randomized controlled trials.