To investigate the benefit of neoadjuvant radiotherapy and adjuvant radiotherapy in elderly and non-elderly patients with rectal mucinous adenocarcinoma, and to analyze the factors influencing the prognosis of patients with rectal mucinous adenocarcinoma.

Based on the Surveillance, Epidemiology, and End Result s database (SEER) of the National Cancer Institute of the United States, 3 997 patients with rectal mucinous adenocarcinoma diagnosed pathologically from 2000 to 2016 were collected. According to the patient′s age, the patients were divided into the elderly group (≥ 60 years old) and the non-elderly group (< 60 years old). The prognosis of the two groups was analyzed and compared. Three treatment methods of the two groups were matched by the propensity score matching method, and the influence of different treatment methods on the prognosis was compared. Kaplan-Meier method was used to draw the survival curve, Log rank test was used to analyze the survival difference of each group, and Cox proportional risk model was used to analyze the factors affecting the prognosis of patients with rectal mucinous adenocarcinoma.

The overall survival (OS) rate of neoadjuvant radiotherapy was the highest, followed by postoperative radiotherapy, and finally by operation only, there were significant differences between each two groups (χ²=13.117, 22.541; P<0.05). However, the cancer-specific survival rate of the neoadjuvant chemoradiotherapy was significantly higher than that of postoperative radiotherapy (χ²=4.023, P=0.045). After propensity score matching for all data, the overall survival rate of neoadjuvant chemoradiotherapy was significantly higher than that of surgery only (χ²=4.874, P=0.027). The OS (χ²=5.530, P=0.019) and CSS (χ²=4.825, P=0.028) of non-elderly patients after surgery alone were significantly higher than those of postoperative radiotherapy. Elder (≥60 y), male, unchemotherapy, and high TNM stage are the influencing factors of poor OS of patients with rectal mucinous adenocarcinoma. Their HRs are 1.689 (95% CI=1.524~1.871), 1.110 (95% CI=1.007~1.223), 1.549 (95% CI=1.338~1.792), StageⅡ HR=2.675 (95% CI=1.191~6.008), StageⅢ HR=3.617 (95% CI=1.612~8.115), PhaseⅣ HR=10.835(95% CI=4.797~24.474); elder (≥60 y), unchemotherapy, and high TNM stage are the influencing factors of poor CSS in patients with rectal mucinous adenocarcinoma, and their HRs are 1.297 (95% CI=1.156~1.456), 1.344 (95% CI=1.129~1.601), stageⅢ HR=6.365 (95% CI=1.582~25.614), stageⅣ HR=20.957 (95% CI=5.189~84.637).

Elderly patients with rectal mucinous adenocarcinoma may benefit from neoadjuvant radiochemotherapy. For non-elderly patients, the prognosis of radiotherapy is not better than that of surgery alone.