Stereotactic Body Radiation Therapy or Intensity-Modulated Radiation Therapy in Treating Patients With Stage IIA-B Prostate Cancer

Inclusion Criteria:

• Previously untreated (no local therapy such as surgery, radiation cryotherapy,high-intensity focused ultrasound [HIFU], etc.) localized adenocarcinoma of theprostate with the following clinical findings:

• Clinical stage by digital rectal exam of either T1c or T2a/b (limited to oneside of the gland); (American Joint Committee on Cancer [AJCC], version 7) orcT1a-c or 2a or 2b

• Stages T1a-T1b are eligible if patient underwent transurethral prostaticresection (TURP)

• The patient must meet one of the following 3 criteria: 1) Gleason score must beGleason 7(3+4) with a PSA < 20 ng/mL, or 2) Gleason 6 (3+3) with a PSA > 10ng/mL and < 20 ng/mL which is considered intermediate risk and eligible for thestudy (AJCC, version 7), or 3) Group Grade 1 with a PSA > 10 ng/mL and < 20ng/mL or 2 with a PSA < 20 ng/mL

• If patient is receiving a 5-alpha reductase inhibitor at the time ofenrollment, the baseline PSA value may be double the initial value and themedication should be discontinued but a washout period is not required; tobe eligible, a PSA drawn while still on the medicine must be:

• < 10 ng/mL if Gleason 7(3+4) (note this patient would be onstratification level 1 if PSA < 5 ng/mL and stratification level 2 ifless than 10 ng/mL)

• > 5 ng/mL and less than 10 ng/mL for Gleason 6(3+3) (note thispatient would be on stratification level 3)

• The prostate volume must be < 70 cc as reported at time of biopsy or byseparate measure with ultrasound or other imaging modalities including magneticresonance imaging (MRI) or computed tomography (CT) scan

• Patients in active surveillance who elect to be treated are eligible if theymeet protocol requirements

• Age >= 18

• History and physical including a digital rectal exam 60 days prior to registration

• Eastern Cooperative Oncology Group (ECOG) performance status 0-1 60 days prior toregistration

• MRI of the prostate and pelvis (per institutional standard of care [SOC] - should becompliant with PIRADSv2.1 guidelines) within 1 year prior to registration

• Bone scan as clinically indicated within 120 days prior to registration

• Charlson modified co-morbidity score =< 4 for patients under 60 and =< 5 forpatients 60 and over 21 days prior to registration

• International prostate symptom score (IPSS) of < 15 21 days prior to registration

• The patient must provide study-specific informed consent prior to study entry

• Willingness and ability to complete the Expanded Prostate Cancer Index Composite (EPIC-26) questionnaire

• Completion of all items of the EPIC-26 which will be data entered at registration 60days prior to registration

• Only English, Spanish, and French-speaking patients are eligible to participate asthese are the only languages EPIC-26 has been validated in

Exclusion Criteria:

• Definitive clinical or radiologic evidence of metastatic disease; no nodalinvolvement or evidence of metastatic disease allowed as defined by screening of thepelvis

• Definitive T3 disease on MRI

• Prior or current invasive malignancy with current evidence of active disease withinthe past 2 years

• Exceptions: Non-melanomatous skin cancer, carcinoma in situ of the male breast,penis, oral cavity, or stage Ta of the bladder, or stage I completely resectedmelanoma

• Prior systemic chemotherapy for the study cancer; note that prior chemotherapy for adifferent cancer is allowable; must be off treatment for at least 3 years

• Prior radiotherapy to the region of the study cancer that would result in overlap ofradiation therapy fields

• The use of hormonal therapy is not allowed; if the patient is on a 5-alpha reductaseinhibitor, then they should be stopped prior to treatment once enrolled onto thestudy; no washout period is required for this study to participate

• Severe, active co-morbidity defined as follows:

• Human immunodeficiency virus (HIV) positive with CD4 count < 200cells/microliter; Note that patients who are HIV positive are eligible,provided they are under treatment with highly active antiretroviral therapy (HAART) and have a CD4 count >= 200 cells/microliter within 30 days prior toregistration; Note also that HIV testing is not required for eligibility forthis protocol; this exclusion criterion is necessary because the treatmentsinvolved in this protocol may be significantly immunosuppressive

• Hepatic insufficiency resulting in clinical jaundice and/or coagulationdefects; note, however, that laboratory tests for liver function andcoagulation parameters are not required for entry into this protocol; (patientson Coumadin or other blood thinning agents are eligible for this study)

• Contraindication to MRI

• Cardiac pacemaker or defibrillator

• Surgically implanted electrical devices such as spinal stimulation devices orintracranial stimulation devices, cochlear implants, the presence of metallicforeign bodies in the orbits, and incompatible old mechanical heart valves andaneurysm clips