(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: The probability of rectal toxicity is higher in patients treated with HDR brachytherapy for prostate adenocarcinoma. The SpaceOAR® hydrogel is of interest to clinicians since it creates space between the prostate and rectum. This study quantifies the impact of SpaceOAR® hydrogel by evaluating the radiation doses to the rectum with and without the hydrogel.
Methods: From March 2017, 36 patients with low and intermediate risk prostate adenocarcinoma (stage >T1c, PSA <10, gleason score > 7) were treated with two fraction HDR brachytherapy to a total dose of 27 Gy. Twelve patients opted for SpaceOAR® hydrogel that was inserted with a needle through the rectourethralis muscle to the perirectal fat. This procedure was performed in the transurethral position with the use of bk 3000 medical ultrasound machine a few days prior to the treatment or on the same day of the flexi-needle (25 or 30cm) implant. Dosimetry was done using the Varian Brachyvision TPS and radiation was delivered using the Varisource iX remote afterloader.
Results: Total of 72 plans were analyzed to obtain the prostate V90, rectum max, mean and V75. Average size of the prostate and SpaceOAR® hydrogel were 65cc and 12cc respectively. Average distance between prostate and rectum was 1.4cm for patients with the hydrogel compared to 0.45cm for patients without the hydrogel. For patients with SpaceOAR® hydrogel compared to the patients without the average rectal doses were: Dmax 9Gy vs 13.7Gy (p<0.05), Dmean 2.5Gy vs 3.4Gy (p<0.05) and V75 0.02cc vs 0.7cc (p<0.05) respectively. Prostate V90 was above 92% in both scenarios.
Conclusion: SpaceOAR® hydrogel is an effective method to create space between the prostate and rectum and reduce radiation dose to the rectum for the patients receiving HDR brachytherapy treatment for prostate cancer.
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