Abstract:

Objective ·To evaluate the survival effects of neoadjuvant radiation therapy and adjuvant radiotherapy on the patients with rectal cancer treated with chemotherapy and surgery by using the Surveillance, Epidemiology and End Results (SEER) database of the United States. Methods ·The patients with pathologically confirmed rectal cancer and treated with chemotherapy and surgical resection from 2005 to 2015 in the SEER database were included; the patients with autopsy or death-only proof of rectal cancer, or without follow-up time and incomplete clinical data were excluded. All the patients were divided into neoadjuvant radiotherapy combined with surgery group (RT+S group), surgical treatment group (S group) and surgery combined with adjuvant radiotherapy group (S+RT group). The propensity score matching (PSM) was used to match the included subjects in each group at the 1∶1 ratio, and the restricted mean survival time (RMST) was used to estimate the mean survival of rectal cancer patients over 5 and 10 years. Cox proportional risk models were used to determine the effects of neoadjuvant and adjuvant radiotherapies on overall survival (OS) and tumor-specific survival (CSS) in the patients with rectal cancer, and the specific benefit groups of neoadjuvant and adjuvant radiotherapies were determined by stratified analysis of patients. Results ·From 2005 to 2015, 8 975 patients with rectal cancer who received chemotherapy and surgery were included, including 1 079 in the S group, 5 991 in the RT+S group, and 1 905 in the S+RT group. After PSM, the clinical base characteristics of the groups were balanced and comparable. The patients in the RT+S group had a significantly improved prognosis in 5 and 10 years compared with the S group (all P=0.000) after PSM, while the patients in the S+RT group had a significantly improved prognosis in 5 years only (both P<0.05) and no significant improvement in 10 years (both P>0.05). Multivariate Cox regression analysis showed that neoadjuvant radiotherapy was an independent protective factor for the patients′ OS and CSS (both P=0.000), while adjuvant radiotherapy was not (both P>0.05). Subgroup analysis showed that neoadjuvant radiotherapy had no significant protective effect on OS and CSS in the patients aged<50 years, with highly differentiated tumors, tumor size≤30 mm or TNM stage Ⅰ?Ⅲ (all P>0.05); whereas adjuvant radiotherapy had significant protective effects on OS and CSS in the patients with poorly differentiated/undifferentiated tumors, tumor size>50 mm or TNM stage Ⅳ (all P<0.05). Conclusion ·For the patients with rectal cancer treated with chemotherapy and surgery, neoadjuvant radiotherapy has a significant survival benefit, but it may not be applicable for the patients aged<50 years, with highly differentiated tumors, tumor size≤30 mm, or TNM stage Ⅰ?Ⅲ; whereas the patients with poorly differentiated/undifferentiated tumors, tumor size>50 mm, or TNM stage Ⅳ may benefit from adjuvant radiotherapy.

Key words: rectum cancer, neoadjuvant radiotherapy, adjuvant radiotherapy, SEER database, prognosis