Stereotactic Body Radiation Therapy in Treating Patients With Prostate Cancer

DISEASE CHARACTERISTICS:

* Histologically confirmed adenocarcinoma of the prostate

  * Stage T1a, T1b, T1c disease
  * Stage T2a or T2b
* No direct evidence of regional or distant metastases
* No T2c, T3, or T4 tumors
* Gleason score ≤ 7
* Must meet the following criteria:

  * Prostate-specific antigen (PSA) ≤ 20 ng/mL prior to starting hormonal therapy (if given) for patients with a Gleason score of 2-6
  * PSA ≤ 15 ng/mL prior to starting hormonal therapy (if given) for patients with a Gleason score of 7
  * Risk of pelvic lymph node involvement \< 20% according to Roach formula
* Ultrasound-based volume estimation of the prostate gland ≤ 60 g

PATIENT CHARACTERISTICS:

* Zubrod performance status 0-2
* Fertile patients must use effective contraception
* No prior invasive malignancy, except for nonmelanoma skin cancer, unless disease-free for a minimum of 3 years (e.g., carcinoma in situ of the breast, oral cavity, or cervix are allowed)
* No significant urinary obstructive symptoms

  * American Urological Association (AUA) score of ≤ 15 (alpha blockers allowed)
* No history of inflammatory colitis (including Crohn disease and ulcerative colitis)
* No history of significant psychiatric illness
* No severe, active comorbidity including any of the following:

  * Unstable angina and/or congestive heart failure requiring hospitalization within the past 6 months
  * Transmural myocardial infarction within the past 6 months
  * Acute bacterial or fungal infection requiring intravenous antibiotics at the time of registration
  * Chronic obstructive pulmonary disease exacerbation or other respiratory illness requiring hospitalization or precluding study therapy within 30 days prior to registration
  * Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects

    * Laboratory tests for liver function and coagulation parameters are not required for entry into this protocol
  * AIDS (based on current CDC definition) or other immunocompromising condition

    * HIV testing is not required for entry into this protocol

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* More than 9 months since prior hormonal therapy as neoadjuvant therapy or to downsize the prostate gland
* No prior pelvic radiotherapy
* No prior chemotherapy or surgery for prostate cancer
* No prior transurethral resection of the prostate (TURP) or cryotherapy to the prostate
* No plans for other concurrent post-treatment, adjuvant, antineoplastic therapy including surgery, cryotherapy, conventionally fractionated radiotherapy, hormonal therapy, or chemotherapy as part of the treatment for prostate cancer