Incidence of acute and delayed rectal toxicities following hydrogel spacer insertion in men receiving dose-escalated radiotherapy for prostate cancer

Objectives: The objective of this study was to evaluate the effectiveness of a hydrogel spacer in reducing acute and delayed rectal toxicities.Materials and Methods: Patients undergoing definitive radiotherapy between January 2015 and March 2018 were retrospectively identified from our institutional cancer registry. Planning data were collected on dose-volume histograms (DVH) for V65, V70 and V75 Gy. All patients underwent definitive volumetric modulated arc therapy (VMAT) of 78 Gy over 39 fractions in a single centre. Toxicity reporting and definitions were in accordance with Common Terminology Criteria for Adverse Events (CTCAE) guidelines.Results: A total of 162 patients received radiotherapy during the study period (spacer n = 80; no spacer n = 82). Baseline characteristics between groups were comparable. Acute rectal toxicity was documented in 19 men (24%) with spacer versus 36 men (44%) without spacer devices (p = 0.007). Over a median post-treatment follow-up period of 17 months (range = 3-38 months), there was a significant reduction in delayed toxicity in men with spacers compared to men without (17 men 21% vs. 31 men 39%, p = 0.021).Conclusion: Hydrogel spacer devices reduce rectal radiation exposure in prostate cancer patients undergoing radiotherapy. This translates into a clinical benefit in terms of acute and delayed rectal toxicities.Level of evidence: cohort study