The use of hydrogel spacer in men undergoing high-dose prostate cancer radiotherapy: results of a prospective phase 2 clinical trial.

Purpose: The purpose of this study was to determine whether the degree of prostate to rectal separation using a hydrogel spacer (HS) and its effect on decreasing rectal dose can be reproduced in the community setting.

Methods: Thirty one patients with cT1-3aN0M0 prostate adenocarcinoma receiving radical radiotherapy to 78 Gy were recruited to the study. The primary endpoint was the proportion of patients achieving at least 25% reduction in volume of rectum receiving 70 Gy (rV70). Other endpoints included degree of prostate to rectum separation, HS insertion-related adverse events and the proportion of patients with grade 1 or worse acute or late gastrointestinal (GI) and genitourinary (GU) toxicity.

Results: All patients had successful insertion of their HS with no peri-operative toxicity. The mean prostate-rectal separation achieved was 10.5 mm. Twenty nine (93.5%) patients achieved a reduction in rV70 of at least 25%. Acute grade 1 GI toxicity was reported in 3 patients. All symptoms had resolved by 3 months post RT. Late grade 1 GI toxicity was reported in one patient (3.2%) with bowel frequency occurring at 6 months and resolving by 12 months post RT. There was no grade 2 or 3 acute or late GI toxicity seen.

Conclusion: In conclusion, this study illustrates that the application and benefits of HS on reducing GI rectal dose endpoints and toxicities during prostate cancer RT can be reliably replicated in a community setting similar to centres participating in the randomised trial under high quality assurance trial monitoring.