Hyaluronic acid rectal spacer improves safety outcomes of hypofractionated RT for prostate cancer

Rectal spacing with hyaluronic acid helps lessen rectal dosimetry and mitigate the gastrointestinal (GI) toxicity associated with hypofractionated radiation therapy (RT) for prostate cancer, according to a study.

A total of 201 men (mean age 68 years, 76.1 percent White) with biopsy-proven, T1 to T2 prostate cancer with a Gleason score of ≤7 and prostate-specific antigen level ≤20 ng/mL were included in the study. They were randomly assigned to receive hyaluronic rectal spacer (n=136) or not (n=65) during hypofractionated RT.

The primary outcome was the percentage of patients who achieved at least a 25-percent reduction in rectal volume receiving 54 Gy (V54), while the secondary outcome was the percentage of patients with grade ≥2 GI toxic effects within the first 3 months. Patients were stratified by intended 4-month androgen deprivation therapy use and erectile quality.

The study met its primary efficacy endpoint, with rectum V54 reduced by at least 25 percent in 98.5 percent of patients in the spacer group. This percentage was greater than the minimally acceptable 70 percent (p<0.001). The mean reduction in rectum V54 was 85.0 percent.

Additionally, significantly fewer patients in the spacer group than in the no-spacer group had acute grade ≥2 GI toxic effects (2.9 percent vs 13.8 percent; difference, −10.9 percent, 95 percent 1-sided upper confidence limit, −3.5; p=0.01).

The findings suggest that rectal spacing may be useful for minimizing the risk of acute grade 2 or higher toxic effects for hypofractionated RT.