RATIONALE: Internal radiation therapy uses radioactive material placed directly into or near a tumor to kill tumor cells.

PURPOSE: This clinical trial is studying the side effects and how well internal radiation therapy works in treating patients with prostate cancer.

OBJECTIVES:

Primary

• To assess the feasibility of high-dose rate (HDR) brachytherapy (without the use of external-beam radiotherapy) as definitive treatment for patients with intermediate-risk prostate cancer.
• To assess acceptable toxicity, defined as treatment related toxicity (urinary and rectal), no worse than that seen by patients treated with conventional therapy (grade 3 urinary toxicity < 10% and grade 3 rectal toxicity < 10%).

Secondary

• To achieve adequate dosimetric coverage of the prostate comparable to current standards.
• To assess the effect of treatment on sexual function.

OUTLINE: Patients undergo 4 high-dose rate brachytherapy treatments over 2 days.

Patients complete bladder, bowel, sexual function, and quality of life questionnaires, including the International Index of Erectile Function (IIEF) questionnaire, the International Prostate Symptom Score Index (IPSS), and the MSKCC Prostate Quality of Life questionnaire at baseline and then at every follow-up visit.

After completion of study treatment, patients are followed every 3 months for 1 year.

DISEASE CHARACTERISTICS:

Inclusion criteria:

• Intermediate-risk adenocarcinoma of the prostate, defined by 1of the following criteria:

  • PSA 10-20 ng/mL
  • Gleason score ≥ 7
  • Stage ≥ T2b AND < T3

• Less than 20% risk of seminal vesicle involvement or lymph node involved based upon the Kattan nomogram (pre-treatment risk with IMRT)

• Prostate size < 60 cc by MRI or CT imaging

• International Prostate Symptom Score Index ≤ 15

Exclusion criteria:

• Evidence of definitive extracapsular extension/seminal vesicle invasion or pelvic adenopathy by MRI (endorectal coil) and DRE (digital rectal examination)

  • Suspected extracapsular disease will not be considered an exclusion criteria

• PSA > 20 ng/mL

• Presence of distant metastases

PATIENT CHARACTERISTICS:

• WBC ≥ 3,500/mm³
• Platelet count ≥ 75,000/mm³
• Hemoglobin ≥ 10 g/dL
• Creatinine ≤ 1.5 mg/dL
• Liver function tests ≤ 1.5 times normal
• INR ≤ 2.5
• Able to complete quality of life questionnaires
• Able to give informed consent
• No active perineal infections
• No history of urethral stricture
• No prior history of pelvic malignancy
• No prior history of lymphoma disease, ulcerative colitis, or anal fissures
• No contraindications to general anesthesia
• No pacemaker

PRIOR CONCURRENT THERAPY:

• No prior transurethral resection of the prostate
• No prior pelvic radiotherapy
• No prior treatment for prostate cancer except for hormone therapy