Inclusion Criteria

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