Hydrogel spacer may reduce rectal irradiation in patients receiving RT for prostate cancer

Injection of a hydrogel spacer in men with prostate cancer receiving radiotherapy was safe and provided prostate-rectum separation sufficient to reduce v70 rectal irradiation, according to findings from a recent study.¹

The results, which were published in JAMA Network Open, also showed that patients who received the hydrogel spacer experienced fewer rectal toxic effects and had a higher bowel-related quality of life (QoL) in late follow-up.

“The rectum is the dose-limiting structure in men receiving radiotherapy for prostate cancer; therefore, strategies that allow dose escalation while decreasing rectal irradiation may optimize local tumor control with fewer bothersome bowel symptoms,” the authors wrote. “Overall, these results suggest that injection of an absorbable perirectal hydrogel spacer prior to RT for prostate cancer may reduce rectal irradiation and the associated rectal toxic effects that manifest clinically after longer-term follow-up.”

Data for 1011 patients from 7 studies were included in the systematic review. These trials comprised 6 cohort studies and 1 randomized clinical trial. Overall, 486 patients received the hydrogel spacer and 525 patients did not. The median follow-up was 26 months (range, 3-63 months).

Placement of the hydrogel spacer was successful in 97% of the intervention arm. In these patients, the weighted mean perirectal separation distance was 11.2 mm. Procedural complications were found to be mild and transient, occurring in only 0% to 10% of the study participants.

Patients in the hydrogel spacer cohort received 66% less v70 rectal irradiation compared with controls (3.5% vs 10.4%; mean difference, -6.5%; 95% CI, -10.5% to -2.5%; P = 0.001 [6 studies]).

In early follow-up, the risk of ≥grade 2 rectal toxic events was comparable between the 2 study arms, occurring in 4.5% versus 4.1% of the intervention versus control arms, respectively (risk ratio, 0.82; 95% CI, 0.52-1.28; P = .38 [6 studies]). In late follow-up, however, the risk was 77% lower in the hydrogel spacer group (1.5% vs 5.7%; risk ratio, 0.23; 95% CI, 0.06-0.99; P = .05 [4 studies]).

A similar trend was observed with changes in bowel-related QoL. In early follow-up, bowel-related QoL was similar between the intervention and control arms (mean difference, 0.2; 95% CI, -3.1 to 3.4; P = 0.92 [2 studies]). In late follow-up, however, the changes in bowel-related QoL were higher in the hydrogel spacer group (mean difference, 5.4; 95% CI, 2.8-8.0; P <.001 [2 studies]).

“Despite the observed results in late follow-up with the hydrogel spacer, it is plausible that the duration of individual studies was insufficient to fully characterize the true magnitude of rectal toxic effects after [radiotherapy],” the authors wrote. “Thus, the clinical benefit of the perirectal spacer may potentially be underestimated in this review owing to limited duration of follow-up. Unfortunately, the number of studies providing results was insufficient to explore the association between follow-up duration and late grade 2 or higher rectal toxic effects.”

Though the investigators did indicate that the hydrogel spacer has a favorable risk-benefit profile for patients receiving radiotherapy for prostate cancer, it was also suggested that additional studies with adequate follow-up durations may help to provide more reliable estimates with regard to the safety and effectiveness of hydrogel spacers.

“The limitations of this review that may confound interpretation were a small number of eligible studies, the predominance of nonrandomized study designs with associated risks of bias, and follow-up durations that may be inadequate to detect long-term clinical manifestations of rectal irradiation,” the authors wrote.

Reference

1. Miller LE, Efstathiou JA, Bhattacharyya SK, Payne HA, Woodward E, Pinkawa M. Association of the placement of a perirectal hydrogel spacer with the clinical outcomes of men receiving radiotherapy for prostate cancer. JAMA Netw Open. 2020;3(6):e208221. doi: 10.1001/jamanetworkopen.2020.8221