Association Between Brachytherapy and Acute Diarrhea During Chemoradiotherapy for Cervical Cancer: A Multicenter Retrospective Study

Background/Aim: Concurrent chemoradiotherapy (CCRT) consisting of external beam radiotherapy (EBRT) and brachytherapy (BT) combined with cisplatin is a standard treatment for cervical cancer. Acute diarrhea is a common gastrointestinal toxicity associated with CCRT. Although dose–volume histogram (DVH) parameters for radiation of the small bowel have been identified as risk factors for diarrhea, the independent contribution of BT has not been well characterized. This study aimed to investigate the association between BT and the development of acute diarrhea. Patients and Methods: We analyzed a multicenter retrospective cohort of 688 patients with cervical cancer who underwent CCRT at 14 institutions in Japan between January 2016 and March 2024. Associations between BT administration, the number of BT fractions, and the occurrence of acute diarrhea were assessed using univariate and multivariate logistic regression analyses. Results: The incidence of acute diarrhea was significantly higher in the BT group than in the non-BT group [88.59% vs. 78.26%; adjusted odds ratio=2.15; 95% confidence interval (CI)=1.35-3.43; p=0.001]. When stratified by the estimated number of BT fractions, patients receiving three fractions demonstrated significantly higher rates of diarrhea compared with those who did not receive BT. Conclusion: In patients with cervical cancer undergoing CCRT, BT was significantly associated with the occurrence of acute diarrhea. The inclusion of BT into a treatment plan may serve as a pragmatic surrogate marker for elevated risk of acute diarrhea in clinical practice. Future prospective studies incorporating detailed information on the timing of diarrhea onset and comprehensive radiotherapy schedules are warranted to better define the causal relationship between BT and acute gastrointestinal toxicity.