A multi-institutional clinical trial of rectal dose reduction via injected polyethylene-glycol hydrogel during IMRT for prostate cancer: Analysis of dosimetric outcomes
Abstract
Purpose To characterize the effect of a prostate-rectum spacer on dose to rectum during external beam radiotherapy for prostate cancer, and to assess for factors correlated with rectal dose reduction. Materials and methods Fifty-two patients at 4 institutions were enrolled onto a prospective pilot clinical trial. Patients underwent baseline scans, then were injected with perirectal spacing hydrogel and re-scanned. IMRT plans were created on both scans for comparison. Objectives were to establish rates of creation of ≥7.5mm of prostate-rectal separation, and decrease in rectal V70 of ≥25%. Multiple regression analysis was performed to evaluate associations between pre- vs. post-injection changes in rectal V70 and changes in plan conformity, rectal volume, bladder volume, bladder V70, PTV volume, as well as post-injection mid-gland separation, gel volume, gel thickness, length of PTV/gel contact, or gel left-to-right symmetry. Results Hydrogel resulted in ≥ 7.5mm prostate-rectal separation in 95.8% of patients; 95.7% had decreased rectal V70 of ≥ 25%, with mean reduction of 8.0 Gy. There were no significant differences in pre- and post-injection prostate, PTV, rectal, and bladder volumes. Plan conformities were significantly different pre- vs. post-injection (P = 0.02); plans with worse conformity indexes post-injection compared to pre-injection (n=13) still had improvements in rectal V70. In multiple regression analysis, greater post-injection reduction in V70 was associated…
How strong is the evidence?
Evidence Hub reads this as a clinical trial, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 13 participants or records.
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