The role of radiotherapy in small cell carcinoma of the esophagus: a retrospective study.

Background: Primary small cell carcinoma of the esophagus (SCCE) is an aggressive carcinoma with a rare incidence. Most patients were diagnosed with stage III-IV and have a poor prognosis. The poor therapeutic outcomes of SCCE reveal the need for more rational therapies.

Methods: We retrospectively reviewed 15,463 patients with esophageal carcinoma from January 2015 to December 2020. 235 (1.52%) patients were pathologically diagnosed with primary SCCE. Clinical characteristics and treatment information were extracted from medical records. All statistical analyses were performed with the SPSS software. Patients were divided into radiotherapy (RT) group and non-RT group. The chi-square test was conducted to analyze the difference in baseline characteristics and propensity score matching (PSM) was used to balance the patient characteristics. Univariate and multivariate analysis was used to identify independent prognostic factors and calculated the estimated hazard ratio (HR) and 95% confidence interval (CI). The Kaplan-Meier method was used to draw survival curves, calculate the median overall survival (OS), and compare prognosis between groups with the log-rank p test. The two-tailed p value less than 0.05 indicated a significant difference.

Results: The median OS was 15.2 months (range:13.4-17.1 months). The addition of RT improved median OS from 14.3 months to 16.5 months, but the difference was not statistically significant (p = 0.657). After PSM, the median OS of the RT group was longer than the non-RT group (16.5 months vs. 11.5 months, p < 0.001). Multivariate analysis identified RT (HR: 0.711, 95%CI: 0.533-0.949, p = 0.020), surgery (HR: 0.490, 95%CI: 0.365-0.660, p < 0.001), and smoking history (HR: 1.335, 95%CI: 1.010-1.765, p = 0.042) as independent prognostic factors. Subgroup analysis showed that RT was not a prognostic factor in patients with surgery (p = 0.450), but could significantly improve OS in patients without surgery (HR: 0.585, 95%CI: 0.415-0.824, p = 0.002). Both middle and lower thoracic SCCE patients could benefit from the addition of RT. RT could improve OS regardless of Ki67 expression level. Subgroup analyses also indicated that stage IV, age ≥ 60, no smoking history, pure SCCE, Syn-positive, CgA-positive, CD56-positive patients could benefit from RT.

Conclusions: SCCE patients could benefit from RT, especially those without surgery. Further studies are required for confirmation of the conclusion.