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.
Aged 18 to 75 years, regardless of gender;
Fully understand this study and voluntarily sign the informed consent form, able to comply with the study protocol and complete all trial procedures;
Patients pathologically diagnosed with rectal cancer;
Undergoing conventional pelvic radiotherapy (total dose of 40-50.4Gy in 25-28 fractions);
Severe comorbidities, including uncontrolled stable medical diseases after treatment, or a history of neurological or psychiatric disorders (such as dementia or epilepsy), making them unsuitable for radiotherapy;
Patients who have received pelvic radiotherapy;
Presence of malignant pleural effusion or malignant abdominal effusion, or accompanied by bowel obstruction;
Pregnant or breastfeeding women;
Parallel
Experimental Group (dexamethasone enema)
DrugPatients will receive enema (dexamethasone 1 mL + normal saline to total 30 mL) once daily from day 10 of radiotherapy until radiotherapy completion.
Control group (dexamethasone enema)
DrugPatients 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.
Improvement rate of radiation-induced rectal injury
Severity of radiation-induced rectal injury
Assessment criteria: Radiation Therapy Oncology Group/European Organisation for Research and Treatment of Cancer (RTOG/EORTC) late radiation morbidity scoring system, Vienna Rectoscopy Score
completion rate of pelvic radiotherapy
Incidence and severity of adverse events to dexamethasone enema
assessed according to CTCAE v.5
quality of life
Assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30)
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