Using Rectal Hydrogel Spacer for Salvage SABR in Prostate Cancer

There are several single institutional series that have reported their experience with salvage radiotherapy options that include EBRT, LDR and HDR brachytherapy. Gastrointestinal (GI) toxicity with salvage radiotherapy range between14-58%, respectively for patients undergoing re-irradiation. There is a concern for an increased risk of fistula development in these patients who receive second course of radiation. Hypofractionation using SABR has been utilized in the re-irradiation setting for prostate cancer with good tumor control and toxicity outcomes. In order to decrease the rectal toxicity, dose to the rectum should be kept as low as possible. Several techniques can be used to achieve this: tighter dosimetric dose painting, better patient or organ immobilization or use of a biodegradable gel. The Investigators ropose a phase I study to assess placement of a hydrogel spacer between the prostate and rectum, in an effort to decrease toxicity and improve patient's bowel quality of life.