Perirectal Hydrogel Spacer Associated with Favorable Radiotherapy Outcomes

New Orleans—During prostate radiotherapy, prostate-rectum proximity can result in rectal irradiation, which limits the use of dose escalation and hypofractionation protocols. Though absorbable perirectal spacers are an option for the reduction of rectal irradiation, none have been studied in randomized, controlled trials. A study presented by Christopher Pieczonka, MD, during a session at the AUA 2015 Annual Meeting, was the first prospective, randomized, controlled study of a perirectal spacer.

A total of 222 men from 20 centers who had stage T1 or T2 prostate cancer underwent prostate radiotherapy planning. They were then randomized 2:1 to receive transperineal fiducial marker and perirectal hydrogel spacer injection (n=149) or fiducial markers alone (n=73). The treatment group received the SpaceOAR® System. The men then underwent additional prostate radiotherapy planning, followed by 79.2Gy x 44 fraction Image Guided – Intensity Modulated Radiation Therapy. Patients were followed weekly during radiotherapy and again at 3, 6, 12, and 15 months.

The researchers assessed spacer tolerability, perirectal space creation, and impacts on rectal dose and quality of life (QOL).

Baseline characteristics were similar among the treatment and control groups with regard to demographics and medical histories, and 99% of patients who were recruited completed the study.

Antibiotic prophylaxis was administered to 95% of patients, with 36.4%, 31.4%, and 32.2% receiving general, local, and other anesthesia, respectively.

Spacer application was rated easy or very easy 98.7% of the time, with a 99.3% success rate. There was also little or no spacer sensation following application, and mild transient rectal events occurred in 10% of patients, according to the researchers.

They found that perirectal space was 12.6 mm post-implant and 10.9 mm at 12.4 weeks. Spacer application resulted in 25% or greater reduction in rectal V70 dose in 97.3% of patients, with 100% of patients in the spacer group and 92% of patients in the control group meeting dose constraints.

Patients in the treatment group reported less decline in bowel QOL at 6, 12, and 15 months. The treatment group also reported less decline in urinary QOL at 6 months.

No adverse events were attributed to the spacer device, as well as no implant infections, rectal wall ulcerations, or other serious complications.

The researchers concluded, “Hydrogel spacer application allowed for >1 cm perirectal space, resulting in significant reductions in rectal radiotherapy doses and was associated with favorable radiotherapy QOL outcomes. The procedure was straightforward, repeatable, well-tolerated, and safe. Perirectal spacer application has the potential to improve outcomes in patients selecting radiotherapy, while also enabling advanced radiotherapy protocols.”

Source: Pieczonka C, Mariados N, Sylvester J, et al. Perirectal hydrogel spacer application in men receiving prostate radiotherapy: A prospective multicenter randomized controlled trial. Abstract of a presentation at the American Urological Association 2015 Annual Meeting, New Orleans, Louisiana, May 19, 2015.

This study was funded by Augmenix.