Ursodeoxycholic acid for the prevention of severe radiation dermatitis: a single-arm phase I/II trial protocol in patients with breast cancer undergoing postoperative radiotherapy in China

Background Breast cancer poses a significant threat to public health, as demonstrated by its high incidence rate. While postoperative radiotherapy remains an important adjuvant treatment for patients with breast cancer undergoing breast-conserving surgery, radiation-induced dermatitis (RID) is a prevalent side effect, for which no standardised prevention method currently exists. Our previous preclinical research demonstrated that ursodeoxycholic acid (UDCA) significantly reduced radiation-induced skin damage in mice. Therefore, this phase I/II clinical study aims to further evaluate the safety and efficacy of UDCA in preventing RID during adjuvant radiotherapy in patients with breast cancer after breast-conserving surgery. Methods and analysis This single-centre phase I/II clinical study, with a single-arm cohort design in phase II, will include female patients who have undergone adjuvant radiotherapy after breast-conserving surgery for breast cancer. The sample size for the study is 40. Eligible patients will receive adjuvant radiotherapy at a prescribed dose of 50 Gy/25 F to the entire breast and lymphatic drainage area, where indicated, and 66 Gy/33 F to the tumour bed. After each irradiation, a 250 mg dose of UDCA will be topically administered to the irradiated area. Radiological dermatitis and skin temperature were assessed once a week after the initiation of radiotherapy, and haematological toxicity, radiation lung injury and quality of life were monitored and analysed on a regular basis until the second week after the conclusion of radiotherapy. The primary objectives of phase I and II studies are the safety profile and incidence of grade II or higher RID in patients, respectively. Ethics and dissemination This study was approved by the ethics committee of Mianyang Central Hospital, China (No: S20230211-02) and is registered in the Chinese Clinical Trial Register (registration number: ChiCTR2400085925). Results will be published in peer-reviewed journals. Trial registration number ChiCTR2400085925.