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In this study, investigators found that the hydrogel spacer has a favorable risk-benefit profile for patients receiving radiotherapy for prostate cancer.
For men receiving prostate radiotherapy, injection of a hydrogel spacer was safe, provided prostate-rectum separation sufficient to reduce v70 rectal irradiation, and was associated with fewer rectal toxic effects and higher bowel-related quality of life (QoL) in late follow-up compared to those who did not receive a spacer, according to study results published in JAMA Network Open.
“The rectum is the dose-limiting structure in men receiving RT 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.”
The systematic review included 1 randomized clinical trial and 6 cohort studies involving a total of 1011 men, 486 of which received a hydrogel spacer and 525 who did not. The median duration of patient follow-up was 26 months (range, 3-63 months).
Overall, the success rate of hydrogel spacer placement was 97.0% (95% CI, 94.4%-98.8% [5 studies]), and the weighted mean perirectal separation distance was 11.2mm (95% CI, 10.1-12.3 mm [5 studies]). Moreover, procedural complications were found to be mild and transient, only occurring in 0% to 10% of the study participants. Even further, patients in the hydrogel spacer group 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]).
The risk of grade 2 or higher rectal toxic effects was similar between the 2 groups in early follow-up (4.5% in the hydrogel spacer group vs 4.1% in the control group; risk ratio, 0.82; 95% CI, 0.52-1.28; P = 0.38 [6 studies]), however, in late follow-up, was 77% lower in the hydrogel spacer group (1.5% vs 5.7%; risk ratio, 0.23; 95% CI, 0.06-0.99; P = 0.05 [4 studies]). In addition, changes in bowel-related QoL were comparable between the 2 groups in early follow-up (mean difference, 0.2; 95% CI, -3.1 to 3.4; P = 0.92 [2 studies]) but were greater in the hydrogel spacer group in late follow-up (mean difference, 5.4; 95% CI, 2.8-8.0; P < 0.001 [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.
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 Network Open. doi: 10.1001/jamanetworkopen.2020.8221.