Background Pelvic and peritoneal radiotherapy is one of the indispensable methods in the treatment of malignant tumors, while radiation bowel injury caused by radiotherapy is a common clinical complication.

Objective To study the factors influencing radiation-induced rectal injury in gynecologic tumor patients after radiotherapy.

Methods A retrospective analysis of radiation-induced rectal injury in 324 patients who received radiotherapy for gynecological tumors in the First Medical Center of Chinese PLA General Hospital from January 2012 to January 2022 was conducted, and the correlation between related factors and radiation-induced rectal injury was analyzed.

Results The average age of the 324 patients was 51.7 ± 10.0 years old. Two hundred and thirty-three cases (71.9%) experienced radiation-induced rectal injury, which included 142 cases (60.9%) of acute radiation-induced rectal injury and 91 cases (39.1%) of chronic radiation-induced rectal injury. The total radiotherapy dose administered was substantial, resulting in an elevated likelihood of radiation-induced injury to the rectum (OR=1.038, 95% CI: 1.015-1.062, P<0.001). High blood pressure (OR=0.384, 95% CI: 0.163-0.906, P=0.029) and chemotherapy prior to radiotherapy (OR=0.433, 95% CI: 0.237-0.790, P=0.006) had a low likelihood of causing radiation-induced injury to the rectum. The high total dose of radiotherapy (OR=1.041, 95% CI: 1.020-1.062, P<0.001) and synchronous brachytherapy (OR=3.768, 95% CI: 1.974-7.162, P<0.001) had a high likelihood of causing acute radiation-induced rectal injury. The incidence of acute radiation-induced rectal injury decreased when surgery was conducted prior to radiotherapy. (OR=0.522, 95% CI: 0.282-0.968, P<0.001). The occurrence of chronic radiation-induced rectal injury was minimal when chemotherapy was administered prior to radiotherapy (OR=0.459, 95% CI: 0.265-0.794, P=0.005). Obese patients had a high likelihood of chronic radiation-induced rectal injury (OR=2.405 , 95% CI: 1.081-5.347, P=0.031).

Conclusion Patients who receive a high total dose of radiotherapy and concurrent brachytherapy are at a high risk for acute radiation-induced rectal injury. Conversely, patients who undergo surgery prior to radiotherapy and chemotherapy before radiotherapy have a lower probability of experiencing acute and chronic radiation-induced rectal injury. Additionally, obese patients have an elevated likelihood of developing chronic radiation-induced rectal injury.