Room: AAPM ePoster Library
Purpose: To study the impact of SpaceOAR on PTV coverage and rectum sparing in treating prostate cancer with stereotactic body radiation therapy (SBRT).
Methods: 20 prostate cancer patients were prescribed with a SBRT dose of 4250 cGy in 5 fractions. 10 of the patients underwent rectal SpaceOAR insertion. The comparison group consisted of 10 patients without SpaceOAR insertion. All treatments were planned with 2 full arcs using the 6MV FFF beam. All plans met dose constraints for PTV coverage and OAR sparing as per our department prostate SBRT treatment directive. The D95 to PTV and rectum dose to 0.01 cc, 1 cc and 3.5 cc were analyzed and compared between those two groups of patients.
Results: The average D95 to PTV in SpaceOAR patients was 96.0% which is 2.2% higher than that to the patients without SpaceOAR. The mean values of rectum dose to 0.01 cc, 1 cc and 3.5 cc were 83.4%, 65.6% and 53.5% of the prescribed dose, respectively, for SpaceOAR patients. In comparison, the mean values were 99.1%, 92.0% and 79.5%, respectively, for patients without SpaceOAR.
Conclusions: SpaceOAR insertion allowed for better PTV coverage posteriorly while helping reduce dose to the rectum significantly, therefore lowering patient morbidity and improving the quality of life.