Proposed Hydrogel-Implant Quality Score and a Matched-Pair Study for Prostate Radiation Therapy.

PURPOSE

SpaceOAR hydrogel has been Food and Drug Administration approved to reduce rectal toxicity in prostate radiation therapy. Training and certification for this procedure is performed by the manufacturer, without independent quality measures. We propose a Hydrogel-Implant Quality Score (HIQS) as a surrogate to quantify hydrogel placement accuracy, to assist clinicians in tracking their implant proficiency, and to support quality improvement. A matched-pair study was designed to investigate the benefit of SpaceOAR in rectal dose reduction for low-dose-rate brachytherapy and to validate the principle of the proposed HIQS.

METHODS

Eighty-one prostate patients were retrospectively selected for this study. Each patient had SpaceOAR implantation under manufacturer supervision. Postprocedure computed tomography and T2-weighted magnetic resonance imaging were acquired for radiation planning. A HIQS system was proposed to evaluate the hydrogel placement quality. Hydrogel implantation was performed immediately after LDR seed placement. For each LDR patient, a non-SpaceOAR patient was matched based upon intraoperative rectal dose and prostate coverage. Intraoperative and postoperative rectal dose reduction was compared between SpaceOAR and non-SpaceOAR groups.

RESULTS

The average HIQS was 77 ± 10.8 (range, 49-97). Rectal anatomic distortions were seen in 17 cases. Significant rectal dose reductions between intraoperative and postoperative plans were found for SpaceOAR patients compared with non-SpaceOAR patients (25.1 Gy vs -5.0 Gy for ΔD and 65.7 Gy vs 13.0 for ΔD). Additional rectal dose reductions (8.4 Gy for ΔD and 12.7 Gy for ΔD) were found for patients without rectal distortion when SpaceOAR was used.

CONCLUSIONS

The proposed HIQS system measured the hydrogel placement quality and provided insights into clinician learning and DVH outcome. SpaceOAR was shown to be effective in reducing rectal dose for LDR patients.