Rectal Spacer Hydrogel Before Radiation Therapy in Reducing Radiation Dose to the Rectum in Patients With Prostate Cancer

The purpose of this research study is to observe the effects of using an FDA-approved rectal spacer device known as the SpaceOAR Hydrogel, which is a soft gel material used to create a space between the rectum and prostate during radiation treatment. The rectal spacer gel is made up of 90% water and 10% polyethylene glycol and is injected as a liquid through a needle inserted between the rectum and prostate. It will stay in place for about 3 months and is naturally absorbed into the body and removed through urine in about 6 months. By pushing the prostate further from the rectum with the hydrogel, it will help spare the rectum from receiving radiation during the standard of care stereotactic body radiation treatment participant will be receiving, along with the brachytherapy treatment. The hydrogel rectal spacer has been shown to be very safe and effective at reducing radiation dose to the rectum during external radiation treatments, but has not been well-studied when using a combination of Stereotactic Body Radiation Therapy (SBRT) and brachytherapy. The goal of this research is to determine how effective the SpaceOAR hydrogel rectal spacer is at decreasing radiation side effects that can occur in the rectum, which can include discomfort or bleeding. The researchers also want to see how the use of this device affects the doctor's ability to perform the brachytherapy implant safely and effectively.