This phase II trial investigates whether proton radiation therapy directed to the prostate tumor, pelvic, and para-aortic lymph nodes, is an effective way to treat patients with high-risk or lymph node positive prostate cancer who are receiving radiation therapy, and if it will result in fewer gastrointestinal and genitourinary side effects. Proton beam therapy is a new type of radiotherapy that directs multiple beams of protons (positively charged subatomic particles) at the tumor target, where they deposit the bulk of their energy with essentially no residual radiation beyond the tumor. By reducing the exposure of the healthy tissues and organs to radiation in the treatment of prostate cancer, proton therapy has the potential to better spare healthy tissue and reduce the side effects of radiation therapy.

PRIMARY OBJECTIVE:

I. To determine the rate of acute grade 2+ gastrointestinal toxicity compared to historical photon treatments.

SECONDARY OBJECTIVES:

I. To determine the rate of acute grade 2+ genitourinary toxicity compared to historical photon treatments.

II. To assess the feasibility of extended-field proton irradiation of high-risk prostate.

III. To demonstrate safety of proton therapy followed by high dose rate (HDR) boost.

IV. To determine patient-reported outcomes (PROs) of toxicity.

OUTLINE:

Patients undergo conventionally fractionated proton beam therapy daily on Monday-Friday. Patients may receive a high-dose rate brachytherapy boost.

After completion of study treatment, patients are followed up at 1, 3, 6, 9 and 12 months, and 1.5, 2, 2.5, and 3 years.

Inclusion Criteria:

• Pathologically confirmed high-risk prostate cancer fulfilling any one of the following criteria:

  • Gleason grade 8 or higher
  • cT3b (seminal vesicle involvement) or cT4
  • Prostate specific antigen [PSA] > 20 (or PSA >10 if on finasteride)
  • Clinically or pathologically positive regional lymph nodes within the inguinal, external iliac, internal iliac, obturator, peri-rectal, pre-sacral, common iliac, or lower para-oaortc (inferior to the L2-L3 interspace) basins

• Zubrod performance status 0-2

• Complete blood cell (CBC)/differential obtained within 90 days prior to registration on study

• Absolute neutrophil count (ANC) >= 1,500 cells/mm^3

• Platelets >= 100,000 cells/mm^3

• Hemoglobin >= 8.0 g/dl (Note: The use of transfusion or other intervention to achieve hemoglobin [Hgb] >= 8.0 g/dl is acceptable)

• Patient must be able to provide study specific informed consent

Exclusion Criteria:

• Absence of bone metastasis by bone scan or metabolic imaging (e.g. NaF PET, FACBC PET, PSMA PET, etc.) before the start of therapy.
• Absence of distant lymph node metastasis by CT and/or MRI before the start of therapy.
• Previous radical surgery (prostatectomy) or cryosurgery for prostate cancer
• Prior radiotherapy, including brachytherapy, to the region of the study cancer that would result in overlap of radiation therapy fields
• Uncontrolled intercurrent illness including, but not limited to, inflammatory bowel disease, human immunodeficiency virus infection, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements

Results of the trial and not individual patient data will be shared. The study protocol, consent, and investigator's brochure will be available. The statistical plan is incorporated into the protocol, along with inclusion and exclusion criteria.