This Study is Evaluating a New Radiation Treatment Technique for Patients Who Have Had Prostate Cancer, Undergone Surgery for Cancer, and Then Have Evidence That Their Prostate Cancer Has Returned.

This will be a two cohort Phase II single center, prospective trial, with a safety lead-in component. This design will allow an initial toxicity assessment phase of a novel radiation treatment schema that is based on other literature, but with limited evidence. There is no plan to escalate the dose. Pending assessment of the safety lead in, complete enrollment will be permitted. Each cohort will be analyzed separated for the safety lead in. There will be 7 patients in the safety lead in cohorts. The stopping point will be an incidence of 2 cases of CTCAE v5.0 Grade 3+ acute toxicity attributed to therapy within gastrointestinal or urinary domains. This generally entails symptoms significant enough to require a procedure or limit basic levels of daily activity (bathing, cooking). Actue toxicity of a comparable magnitude has been reported in the 1-5% rate in a recent meta-analysis of contemporary trials which utilized standard of care radiation. Thus two cases would represent an unacceptable increased toxicity level, and a cohort size of 7 is approximate the commonly accepted size in Phase I escalation studies to evaluate dose limiting toxicity.

Inclusion criteria

• Adenocarcinoma of the prostate with previous surgical resection
• Radiologically detected prostate bed OR regional nodal recurrence defined as iliac, obturator, perirectal or pre-sacral node generally encompassing below the aortic bifurcation
• Prostate bed recurrence as occurring within the region of the prostate or RTOG consensus definition of the surgical field
• At least two serum detectable PSA levels defined as >0.02 ng/dl at least 30 days apart.

Exclusion criteria

• Metastatic disease
• Prior radiation therapy to the pelvis region
• Inflammatory bowel disease
• Hospitalization for a gastrointestinal diagnosis in the preceeding 3 months
• Hospitalization for a urinary tract issue / diagnosis in the preceeding 3 months
• PSA >10 ng/dl at study entry,