Inclusion Criteria:

          -  Pathological (histologically) proven diagnosis of prostatic adenocarcinoma within 365
             days (1 year) prior to study registration.

               -  History and physical exam with digital rectal exam of the prostate to establish
                  clinical staging

               -  Clinical stage T1-T2c (AJCC 7th edition) within 90 days of registration.

               -  Prostate specific antigen (PSA) < 20 ng/mL within 90 days prior to registration.

               -  Gleason Score < 7.

               -  Eastern Cooperative Oncology Group(ECOG) Performance status 0-1.

               -  Clinically negative lymph nodes evaluated by imaging (pelvic +/- abdominal CT or
                  MRI scan).

               -  Patients with lymph nodes equivocal or questionable by imaging are eligible
                  without biopsy if the nodes are ≤ 1.5 cm in diameter; any node larger than this
                  on imaging will require negative biopsy for eligibility, unless the node is know
                  to be enlarged from prior scans and considered stable, per discretion of the
                  treating physician.

               -  Patients must be 18 years of age or older.

               -  Patient must be able to provide study-specific informed consent prior to study
                  entry.

               -  Willingness and ability to complete the Expanded Prostate Cancer Index Composite
                  (EPIC) Questionnaire.

               -  No evidence of bone metastases (M0) on bone scan within 60 days prior to
                  registration.

               -  Bone scan is not required for patients enrolled with a single intermediate risk
                  factor only, but this scan may be obtained at the discretion of the treating
                  physician. Patients with 2 or 3 risk factors will require a negative bone scan
                  for eligibility.

               -  Equivocal bone scan findings are allowed if plain film x-rays are negative for
                  metastasis.

               -  Patient is able to start proton therapy or neo-adjuvant hormonal therapy, when
                  recommended, within 12 weeks of registration.

               -  No prior radiotherapy to the pelvic area.

               -  No prior prostate cancer therapy such as: prostatectomy, cryotherapy,
                  chemotherapy or hyperthermia.

               -  Platelets ≥ 100,000 cells/mm3, Absolute neutrophil count (ANC) ≥ 1,800 cells/mm3,
                  Hemoglobin ≥ 8.0 g/dl (Note: The use of transfusion or other intervention to
                  achieve Hgb ≥ 8.0 g/dl is acceptable.)

               -  Obs.: Patients with high risk factors, such as T3, Gleason 8-10 or PSA > 20ng/mL
                  who are not considered candidates for pelvic lymph node radiation treatment are
                  still considered eligible for this study.

        Exclusion Criteria:

          -  • Prior radiotherapy to the pelvic area.

               -  Prior prostate cancer therapy such as: prostatectomy, cryotherapy, or
                  hyperthermia.

               -  Prior systemic therapy (chemotherapy) for prostate cancer.

               -  Evidence of distant metastases.

               -  Regional lymph node involvement.

               -  Previous or concurrent cytotoxic chemotherapy for prostate cancer.

               -  Acquired Immune Deficiency Syndrome (AIDS) based upon current Centers for Disease
                  Control (CDC) definition. Note however, that HIV testing is not required for
                  entry into this protocol. The need to exclude patients with AIDS from this
                  protocol is necessary because the treatments involved in this protocol may be
                  significantly immunosuppressive. Protocol-specific requirements may also exclude
                  immune-compromised patients.