External Validation of a Survival Score for Limited-Stage Small Cell Lung Cancer Patients Treated with Chemoradiotherapy

Purpose In order to personalize multimodal treatment regimens in limited-stage small cell lung cancer (LS-SCLC), a survival score for these patients was proposed. The aim of this study is to validate the score in an independent external patient cohort. Methods We collected data of 78 patients treated with chemoradiotherapy for LS-SCLC between 2004 and 2015. The survival score was calculated by independent prognostic factors: gender, Karnofsky performance status, tumor substage, and hemoglobin level before treatment. Scoring points were derived from 2-year survival rates divided by 10 and the values for each prognostic factor were tallied. Three risk subgroups were defined (high, intermediate, low risk: 9-13, 14-18, 19-26 points). The 2-year survival rate of each subgroup from the original study was compared to its corresponding subgroup from the validation cohort. Results Median survival time in the entire validation cohort was 17 months (range: 1-123 months). The 2-year survival rates were 0% in the 9-13, 35% in the 14-18, and 43% in the 19-26 points group, respectively (p = 0.018). The difference in 2-year survival between the 9-13 points and the 14-18 points group was significant in the validation cohort (p = 0.007) as well after stratification of concurrent chemoradiotherapy (p < 0.001), whereas the difference between the 14 and 18 points and the 19-26 points group was not significant (p = 0.602, p = 0.770). Conclusion The score was reproducible to estimate the 2-year survival rate of patients with LS-SCLC, especially in the high- and intermediate-risk subgroups. In order to improve the differentiation between patients with an intermediate and favorable survival prognosis, the scoring system needs further development.