Hydrogel Spacing for Radiotherapy of Prostate Cancer: A Review of the Literature

Abstract

IntroductionThe rectum is particularly sensitive to radiation and it represents the dose limiting structure during radiation therapy for prostate cancer. Transperineally inserted rectal hydrogel spacers were proposed as a technique to limit the rectal radiation dose and rectal toxicity during prostate radiation therapy. MethodsDifferent spacing materials, including hyaluronic acid, polyethylene glycol and human collagen, have been tested as potential rectal spacing agents to reduce radiation exposure to the rectum and limit rectal toxicity. ResultsEarly results from studies in which 1 to 48 patients received rectal spacers demonstrate that rectal spacers during prostate radiation therapy appear to be feasible and tolerable, and are not associated with significant side effects. The published literature shows a median or mean space achieved between the rectum and prostate that typically ranges from 1.0 to 2.0 cm, significant reductions in rectal radiation dose, a low rate of acute gastrointestinal toxicity and short-term quality of life benefits when comparing men who receive rectal spacers during prostate radiation therapy to those who do not. ConclusionsRectal spacers could potentially allow for greater dose escalation and hypofractionation while reducing rectal toxicity or protecting against increased rectal toxicity. This could theoretically lead to better tumor control, decreased toxicity and health care costs, and improved patient and provider satisfaction. Although short-term results based on the small cohort studies summarized in this review are encouraging, longer followup and larger, randomized trials are needed to determine the impact of rectal spacers on tumor control and late rectal toxicity.