High‐dose rate endorectal brachytherapy for rectal cancer: A state‐of‐the‐art review

Rectal cancer is a common malignancy that requires multidisciplinary treatment. By utilizing the dose–response relationship in rectal cancer radiotherapy, increasing the radiotherapy dose can improve clinical complete remission rates. High‐dose rate endorectal brachytherapy (HDREBT) is a novel technique that delivers high doses of radiotherapy directly to the tumor via an endorectal applicator, sparing the adjacent normal tissues from excessive radiation exposure. HDREBT includes contact X‐ray brachytherapy and high‐dose‐rate intracavitary brachytherapy. We introduce the latest developments in applicators and imaging techniques for HDREBT in rectal cancer and summarize the current evidence on the efficacy, safety, and feasibility of HDREBT as a neoadjuvant, definitive, or palliative treatment option for all stages of rectal cancer patients. We also discuss the potential advantages and challenges of HDREBT in achieving organ preservation and improving the quality of life of rectal cancer patients. HDREBT has shown promising results in achieving high complete response rates, enabling nonoperative management, improving organ preservation rates, and providing effective palliation in rectal cancer patients. More studies are needed to optimize its dose and fractionation schemes in different clinical scenarios.