Rectal Spacer Evidence: Acute Toxicity, Durability, and Safety

In this installment, Daniel Welchons, MD, walks through the pivotal 2023 hyaluronic acid spacer (Barrigel) trial, a 201-patient study across 12 centers in the US, Australia, and Spain among men receiving moderately hypofractionated prostate radiotherapy. Nearly 99% of spaced patients achieved a greater than 25% reduction in V54, and grade 2 or greater acute GI toxicity within 3 months fell to 2.9% in the spacing group vs 13.8% in unspaced patients. Aurelie Garant, MD, highlights that patient-reported quality-of-life data matter as much as physician-graded toxicity, noting that even lower-grade symptoms such as tenesmus and urgency can meaningfully disrupt patients' daily lives and social routines.

The discussion then turns to a multi-institutional 3-year follow-up study, which Welchons says found 0% late grade 2 or greater GI toxicity in the spaced cohort vs 9.5% in controls, a statistically significant difference showing that spacing protects against late as well as acute toxicity, an outcome he calls especially important since late effects are often the hardest to treat.

On safety, Welchons cites a 2020 meta-analysis of approximately 1000 patients showing rectal spacing is safe overall, with 97% of procedures completed without complication, although minor effects such as transient perineal discomfort or bleeding can occur. Garant adds trial-level detail: Rectal wall infiltration occurred in approximately 6% of hydrogel cases vs 0.3% with hyaluronic acid spacers among experienced physicians, a gap that widens further in less experienced hands. She describes using minimal ultrasound compression and continuous monitoring during injection to further reduce that risk in her own practice.

In the next episode, "Patient Selection and Partnership in Prostate Radiotherapy Spacing," Welchons and Garant discuss which patients with complex anatomy benefit most from spacing, what it takes to build a strong urology–radiation oncology partnership, and where spacer technology is headed next.