Barrigel is intended to temporarily position the anterior rectal wall away from the prostate or prostate bed during radiotherapy treatment for prostate cancer and, in creating this space, it is the intent of Barrigel to reduce the radiation dose delivered to the anterior rectum.

Barrigel is composed of biodegradable material and maintains space for the entire course of prostate or prostate bed radiotherapy and is intended to be absorbed by the patient's body over time.

To evaluate the safety and effectiveness of Barrigel to reduce the radiation dose delivered to the anterior rectum by creating a space when injected between the rectum and the prostate bed in men receiving definitive external beam radiation therapy (intensity-modulated radiation therapy) for recurrence of prostate cancer after radical prostatectomy.

A prospective, randomized, controlled, single-masked multicenter study.

Inclusion Criteria:

1. Age ≥ 18 years
2. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
3. Prostatectomy surgeon notes specifying successful bilateral nerve Sparing procedure
4. Documentation of an intra or interfascial radical prostatectomy
5. Confirmed diagnosis of adenocarcinoma of the prostate treated primarily with radical prostatectomy with pN0 or pNX pathologic stage
6. No radiographic evidence of local, regional, or distant metastatic disease via PSMA PET or Axumin fluciclovine F18 scan
7. Prostate specific antigen (PSA) 0.1 ng/mL or higher
8. Intent to receive definitive radiation therapy to the prostate bed
9. Written informed consent for study participation prior to study enrollment

Exclusion Criteria:

1. Known allergy to hyaluronic acid
2. Pathologic T4 disease
3. Prior local prostate cancer therapy including cryotherapy or brachytherapy.
4. Prior post-prostatectomy or pelvic radiation therapy
5. Planned elective pelvic lymph node radiation therapy
6. Prior anorectal surgery (e.g. low anterior resection, abdominoperineal resection, absence of a rectum)
7. Inflammatory bowel disease requiring treatment with steroids (e.g. Crohn's disease, ulcerative colitis)
8. Active connective tissue disorder including lupus or scleroderma
9. Any urogenital abnormality that could limit the ability to access the Barrigel injection site
10. White blood cell count <4000/uL or >12,000/uL.
11. Hemoglobin <10 g/dL (transfusion or other intervention to achieve this is acceptable).
12. Active bleeding disorder or clinically significant coagulopathy defined as PTT >35 seconds or INR >1.4 or platelet count <100,000/mm3.
13. Serum AST/ALT >2.5 times the institutional upper limit of normal
14. Creatinine >2.0 mg/dL
15. Bilirubin >2.0 mg/dL
16. History of chronic renal failure.
17. History of uncontrolled diabetes (e.g. symptomatic hyperglycemia that is not controlled with medical management; fasting blood glucose >300 mg/dL).
18. History of acquired immunodeficiency syndrome (AIDS). Patients with controlled HIV infection (CD4+ T-cell counts ≥ 350 cells/µL) and no history of AIDS-defining opportunistic infections may be included.
19. Contraindication to having an MRI or PSMA/PET scan (e.g. non-MRI compatible device).
20. Presence of bilateral hip implants, although unilateral hip implant may be permissible if the implant is MRI compatible and does not produce artifact that interferes with any requirements of the study protocol
21. Subject unable or unwilling to comply with study requirements
22. Any condition that in the investigator's opinion would prevent administration or completion of study therapy

Data will be submitted to FDA as part of a 510(k). Study data will be shared with other researchers for analysis and reporting after FDA clearance, including protocol, SAP, CSR, and raw data.

Within three months of the FDA decision.

Qualified researchers with the intent to publish their results.

All subjects who sign a consent and meet inclusion and exclusion criteria will be randomized to the treatment or the control arm.