Minimizing Rectal Toxicity in Prostate Cancer Radiotherapy: From Anatomical Understanding to Modern Protective Strategies- A Narrative Review

Abstract

Rectal toxicity remains one of the major dose-limiting complications in prostate cancer radiotherapy. Due to the close anatomical proximity between the prostate and rectum, even modest dose escalation may induce mucosal and vascular injury, leading to acute or chronic proctitis. This narrative review summarizes the anatomical and physiological characteristics of the rectum, mechanisms of radiation-induced injury, and current strategies to minimize toxicity. Advances in intensity-modulated and image-guided techniques have significantly reduced rectal exposure; however, residual toxicity persists in a subset of patients. Clinical strategies to mitigate rectal injury include consistent bladder filling and rectal emptying protocols, which enhance treatment reproducibility and reduce high-dose exposure. Mechanical interventions, such as endorectal balloons and implantable rectal spacers, provide additional protection by stabilizing the prostate and creating physical separation from the rectum. Among available devices, hydrogel and biodegradable balloon spacers demonstrate the strongest evidence for lowering rectal dose and improving quality of life. Despite these advances, procedural variations, invasiveness, and limited data for pelvic nodal irradiation remain challenges. Future perspectives include the standardization of protocols, incorporation of adaptive image guidance, and the development of artificial intelligence–based predictive models for personalized rectal protection. A comprehensive understanding of rectal anatomy, dose–volume parameters, and emerging technologies is essential to optimize therapeutic outcomes in prostate cancer radiotherapy.