Long-term Effect of Radiotherapy in Rectal Cancer Patients with Mucinous Tumor: A Large Population Based Study

Due to distinct biological behavior of mucinous adenocarcinoma (MAC) and signet ring cell cancer (SRC), the efficacy of radiotherapy on long-term outcome for rectal cancer (RC) patients with mucinous tumors is still unclear. Here, we identified 1808 RC patients with MAC/SRC from Surveillance, Epidemiology, and End-Results (SEER) database from 2004 to 2013. Patients were divided into two subgroups according to different therapeutic strategies, including surgery alone and surgery combined with radiotherapy. Kaplan-Meier methods and Cox regression models were used to access the influence of therapeutic strategy on long-term survival outcomes. The 5-year and 10-year cancer specific survival (CSS) were improved in stage II and III patients who underwent surgery and radiotherapy compared with patients who underwent surgery alone. These results were further confirmed following propensity score matching. In addition, radiotherapy was deemed as independent good prognostic factor in patient with MAC/SRC. In subgroup analysis, the result also demonstrated that long-term survival was improved following radiotherapy. However, there was no prognostic difference between preoperative and postoperative radiotherapy. In conclusion, radiotherapy could improve survival for RC patients with MAC and SRC, but only for patients in stage II and III. This finding supported the application of radiotherapy in clinical practice.