Presenter(s)
E. Yaghoubian1, B. Venkatesulu2, R. B. Patel3, A. C. Mueller4, M. Yu5, and A. C. Olson6; 1UPMC Hillman Cancer Center, Pittsburgh, PA, 2Loyola University Chicago, Loyola University Medical Center and Edward Hines Jr., VA Hospital, Stritch School of Medicine, Department of Radiation Oncology, Cardinal Bernardin Cancer Center, Maywood, IL, 3Department of Radiation Oncology, University of Pittsburgh School of Medicine; UPMC Hillman Cancer Center, Pittsburgh, PA, 4Department of Radiation Oncology, UPMC Hillman Cancer Center, University of Pittsburgh, Pittsburgh, PA, 5University of Pittsburgh Medical Center, Pittsburgh, PA, 6UPMC-Shadyside Hospital, Pittsburgh, PA
Purpose/Objective(s): Perirectal spacers reduce rectal radiation dose and improve quality of life in patients receiving definitive external beam radiation therapy for prostate cancer. Of three FDA-approved products, two, a PEG-based hydrogel and a Vicryl balloon are used at our institution. We compared spacer quality, symmetry, and early procedural complication rates between these products.
Materials/Methods: We retrospectively identified the first 16 patients receiving the balloon spacer and matched 32 PEG cases (1:2) treated from April 2021 to December 2025. Spacers were placed by experienced urologists or radiation oncologists. Rectal Spacing Quality Score (SQS) and Spacer Symmetry Score (SSS) were assessed using established methodology. Spacer height was measured from posterior prostate capsule to anterior rectal wall. SQS measurements were obtained at rectal midline and 1 cm right/left at three axial levels (base -6 mm, midgland, apex +6 mm). SSS assessed symmetry at midgland plus 1 cm superior and inferior.
Results: Forty-eight cases were analyzed. Median patient age for PEG vs balloon was 66 vs 72 years (p=0.98). Mean prostate volume was 43.6 vs 53.1 cc (p=0.156). Spacer volume was larger with balloon spacers (17.4 vs 8.4 cc, p<0.001). Mean prostate–rectum separation favored balloon spacers at all levels. SQS distributions were similar: PEG, 68.5% highest quality, 14.8% acceptable, 16.6% lowest (mean 1.52); balloon, 77.1% highest, 16.6% acceptable, 6.3% lowest (mean 1.71). Symmetry scores were comparable (mean SSS 1.56 PEG vs 1.50 balloon). One procedural complication occurred (intramural rectal wall placement with PEG) without grade =2 GI toxicity.
Conclusion: Both PEG hydrogel and balloon spacers provided effective prostate–rectal separation with excellent symmetry and low complication rates. Balloon spacers produced larger separation volumes and modestly higher quality scores, though clinical significance remains uncertain. Both products appear safe and effective; further prospective studies including dosimetric and patient-reported outcomes are warranted.
| Distance from Prostate to Rectum (mm) | Spacer Quality Score (%) | Spacer Symmetry Score | ||||||||||||||
| Base-6mm | Midgland | Apex+6mm | 0 = worst, 1 = acceptable, 2 = best | 1 = best to 5 = worst | ||||||||||||
| mean | range | mean | range | mean | range | 0 | 1 | 2 | mean | 1 | 2 | 3 | 4 | 5 | mean | |
| PEG | 11.6 | 0 – 21.8 | 9.8 | 0 – 18.3 | 5.0 | 0 – 15.9 | 16.6 | 14.8 | 68.5 | 1.52 | 24 | 7 | 4 | 1 | 0 | 1.56 |
| Balloon | 15.3 | 3.8-24.2 | 17.0 | 3.9 – 23.9 | 15.0 | 0 – 29.5 | 6.3 | 16.6 | 77.1 | 1.71 | 12 | 1 | 2 | 1 | 0 | 1.5 |