A Comparison Between Rectal Dose in Prostate Radiotherapy Patients Treated with Spaceoar Hydrogel Present Versus Patients Treated Without Spaceoar Hydrogel.

Introduction: External beam radiation therapy is a common treatment option for prostate cancer patients with localized disease. Radiation-induced side effects associated with the rectum can impact a patient’s ability to complete treatment or affect the quality of life years after radiation treatment. Spaceoar hydrogel has been developed to reduce radiation dose to nearby pelvis structures, and therefore decreasing potential side effects. Methods: A total of 20 patients who received definitive radiation therapy to the prostate and seminal vesicles were selected and placed into 2 groups (10 spaceoar, 10 non-spaceoar). The individuals’ age ranged from 60 to 79 years old with a median age of 69 years old. Group 1 received radiation plus spaceoar hydrogel and group 2 received radiation alone. Radiation therapy included 70 Gy to the prostate and seminal vesicles in 2.5 Gy/fraction for a total of 28 fractions. The spaceoar hydrogel was injected prior to radiation therapy CT simulation. Results: The results showed that different dose outcomes between the groups were significant for V70, V65 and V60, and not significant for Mean cGy. The predicted models showed a trend with an increase in rectal volume receiving dose in the non-spaceoar group. Conclusion: Spaceoar hydrogel may help reduce radiation-induced side effects by decreasing dose to the rectum during radiation therapy treatment. With a better understanding of the impact of spaceoar on radiation rectal dose, efforts can be made to optimize the control of potential radiation-induced side effects. This evidence could impact the clinician’s decision to consider the use of spaceoar in their prostate cancer patients who are undergoing radiation therapy