Improvement Effect of Dexamethasone Enema for Acute Radiation-induced Rectal Injury

Research Objective and Principle: Through a randomized controlled study, evaluate the effectiveness of dexamethasone in improving radiation-induced rectal injury in rectal cancer patients undergoing pelvic radiotherapy, thereby providing evidence for treatment options in patients at risk of radiation-induced rectal injury and aiming for adoption in international guidelines. Primary Objective: Improvement rate of radiation-induced rectal injury. Secondary Objectives: Severity of radiation-induced rectal injury, completion rate of pelvic radiotherapy, safety of dexamethasone enema, quality of life, pathological complete response (pCR) rate. Study Design: Prospective, single-center, randomized controlled study. Study Population and Expected Enrollment: Patients with rectal cancer undergoing conventional pelvic radiotherapy, expecting to enroll 40 patients. Trial Duration: From February 2026 to February 2028. Intervention: Experimental Group: Patients will receive enema (dexamethasone 1 mL + normal saline to total 30 mL) once daily from day 10 of radiotherapy until radiotherapy completion. Control Group: Patients will receive enema (dexamethasone 1 mL + normal saline to total 30 mL) once daily from the occurrence of radiation-induced rectal injury until radiotherapy completion. Statistical Hypothesis: Based on previous reports, the incidence of acute radiation-induced rectal injury is 86%, and it is expected that the experimental group can reduce it to 40%. The sample size was estimated using a formula designed to compare 2 proportions, with a set at 0.05 and a power of 80%. The study aimed to enroll at least 36 patients. Considering a dropout rate of 10%, at least 40 patients need to be included.