To demonstrate the effectiveness of the SpaceOAR Vue System in reducing late gastrointestinal (GI) toxicity in subjects undergoing Stereotactic Body Radiotherapy (SBRT) to treat prostate cancer.

This study is designed to evaluate the effectiveness of the SpaceOAR Vue System in reducing late gastrointestinal (GI) toxicity in participants undergoing Stereotactic Body Radiotherapy (SBRT) for the treatment of prostate cancer.

Inclusion Criteria:

• Age ≥ 18 years old.
• Subjects must have pathologically confirmed (by routine hematoxylin and eosin (H&E) staining) invasive adenocarcinoma of the prostate and been planning to undergo SBRT.
• Subjects must have intermediate risk prostate cancer as defined by the presence of one or more of the following:
• Clinical Stage T2b - T2c (AJCC 6th edition) tumor
• Gleason Score 7 as determined from a biopsy taken within 9 months preceding Enrollment (randomization)
• Demonstrated blood PSA levels 10-20 ng/ml as measured within 6 months preceding Enrollment (randomization) and prior to commencing androgen deprivation therapy (ADT)
• Subject or authorized representative was informed of the nature of the study and provided written informed consent, approved by the appropriate Institutional Review Board (IRB)/Ethics Committee (EC) of the respective clinical site.

Exclusion Criteria:

• Prostate >80 cc documented within 9 months preceding Enrollment (randomization)
• Clinical stage T3 or T4 (AJCC 6th edition) tumor
• Blood PSA level >20 ng/ml as measured within 6 months preceding Enrollment (randomization) and prior to commencing androgen deprivation therapy (ADT)
• Gleason Score ≥ 8 as determined from a biopsy taken within 9 months preceding Enrollment (randomization)
• Subjects who had MRI evidence of gross posterior extracapsular extension (ECE) of the prostate cancer. (Note: MRI should be from within 9 months preceding Enrollment (randomization). If MRI is contraindicated, a digital rectal exam may be performed to confirm the absence of gross posterior ECE)
• Subjects who had metastatic disease, other ongoing cancers which were treated during the study or subjects for whom pelvic lymph node radiotherapy was planned.
• Subjects with any prior invasive malignancy (except non-melanomatous skin cancer) unless the subject had been disease free for a minimum of 3 years.
• History of prostatectomy, transurethral prostate surgery (e.g. TUNA, TUMT, TURP) if performed within 1 year prior to screening, other local prostate cancer therapy (e.g., cryotherapy or brachytherapy) or previous pelvic irradiation at any time prior to screening.
• History of prior pelvic surgery requiring low anterior or abdominoperineal resections or rectal surgery.
• History of or active inflammatory bowel disease (IBD) such as Crohn's disease or ulcerative colitis.
• History of or current perirectal disease that may interfere with interpretation of study outcomes including anal or perianal diseases such as fistula.
• Bleeding hemorrhoids requiring medical intervention within the prior three months.
• Diagnosed active bleeding disorder or a clinically significant coagulopathy. Note: Patients on anticoagulants may be included if the anticoagulant medication can be discontinued for index procedure.
• Active inflammatory or infectious process involving the perineum, gastrointestinal (GI) or urinary tract based on positive diagnosis or suspected diagnosis in the presence of fever >38⁰ C, WBC > 12,000/uL.
• Compromised immune system or prior diagnoses for human immunodeficiency virus (HIV) (with a detectable viral load within the last 6 months)/acquired immunodeficiency syndrome (AIDS) or autoimmune disease.
• If a subject was enrolled in another investigational drug or device trial that had not completed the primary endpoint or that clinically interfered with this study.
• Unable to comply with the study requirements or follow-up schedule.
• Any condition the Investigator believed would interfere with the intent of the study or would make participation not in the best interest of the patient.
• Known iodine sensitivity or allergy
• Known polyethylene glycol (PEG) sensitivity or allergy