A Prognostic Scoring Model to Determine Which Patients with Metastatic Extensive-stage Small Cell Lung Cancer Could Benefit from Local Radiotherapy: a Large Population-based Study

Objective: Our study was performed to clarify which patients with metastatic extensive-stage small cell lung cancer (ES-SCLC) could gain survival benefit from local radiotherapy. Patients and Methods: A chi-square test was used to compare baseline characteristics of different groups. Kaplan-Meier method was applied to analyzing the survival difference. The prognostic factors for cancer-specific survival (CSS) in patients receiving radiotherapy were analyzed by the Cox proportional hazard model. According to the above information, we established a prognostic score model. Based on the prognostic score model, the Kaplan-Meier method was used to make survival curves to find the difference in prognosis. CSS based on different subgroup variables were analyzed by the Cox proportional hazard model and concrete results were shown in forest plots. Results: Our study revealed that CSS improved in the radiotherapy group compared with the control/none group (P<0.001). The multivariate analysis identified that both female and metastasis number=1 as significant prognostic factors for favorable CSS. We established a prognostic score (PS) model with a score of 0 to 2. Based on the prognostic score model, survival curves were made and showed that CSS of the radiotherapy group improved significantly with the decreasing patient propensity score (P<0.001). In subgroup analyses, patients with PS=0 (P<0.001) and PS=1 (P<0.001) could benefit from receiving local radiotherapy; patients with PS=2 (P=0.160) demonstrated no significant difference in CSS after receiving local radiotherapy. Conclusions: Local radiotherapy could improve the CSS of patients with metastatic ES-SCLC, only for patients with a 0-1 score.