RATIONALE: Stereotactic radiation therapy may be able to send x-rays directly to the tumor and cause less damage to normal tissue.

PURPOSE: This trial is studying the side effects of stereotactic radiation therapy and to see how well it works in treating patients with prostate cancer.

OBJECTIVES:

Primary

• To estimate in both low- and low-to-intermediate-risk groups of patients with prostate cancer, the rate of acute toxicities observed during the 5 years following CyberKnife® stereotactic radiosurgery (SRS).

Secondary

• To estimate the rate of late grade 3-5 toxicities after SRS in these patients.
• To measure biochemical disease-free survival of patients treated with this therapy.
• To measure rates of local failure, distant failure, disease-free survival, disease-specific survival, and overall survival of patients treated with this therapy.
• To measure quality of life in generic and organ-specific domains in patients treated with this therapy.
• To evaluate imaging modalities and their potential role in the detection of prostate cancer persistence, recurrence, and/or progression in patients treated with this therapy.

OUTLINE: Patients are stratified according to risk group (low risk vs low/intermediate risk).

Patients undergo fiducial placement using ultrasound. At least 5-10 days later, patients undergo CyberKnife® stereotactic radiosurgery once daily for 5 days.

Patients complete 4 questionnaires at baseline and periodically during study to assess acute and late toxicities and quality of life (e.g., overall health status, patient function, sexual function, and urinary symptoms).

After completion of study therapy, patients are followed for up to 5 years.

DISEASE CHARACTERISTICS:

• Histologically confirmed adenocarcinoma of the prostate

  • Disease confirmed by biopsy within 1 year of study entry
  • Gleason score 2-7(3+4)

  • Clinical stage T1a or T2b, N0 or NX, M0 or MX

    • T- stage and N-stage determined by physical exam and available imaging studies (i.e., ultrasound, CT scan, and/or MRI)

    • M-stage determined by physical exam, CT scan, and/or MRI

      • Bone scan is not required unless clinical findings suggest possible osseous metastases
• PSA ≤ 10 ng/mL within the past 60 days

• At risk for recurrence, as defined by 1 of the following risk groups:

  • Low-risk, defined by the following combination:

    • Stage T1a-T2a, Gleason 2-6, and PSA ≤ 10 ng/mL

  • Low- to-Intermediate-risk, defined by either of the following combinations:

    • Stage T2b, Gleason 2-6, and PSA ≤ 10 ng/mL
    • Stage T2b, Gleason 3+4=7, and PSA ≤ 10 ng/mL

• Prostate volume must be ≤ 100 cc

  • Determined by measurement from CT scan or ultrasound within the past 90 days or within the past 14 days if hormone therapy is given

PATIENT CHARACTERISTICS:

• ECOG performance status 0-1
• No implanted hardware or other material that would prohibit appropriate treatment planning or treatment delivery, in the investigator's opinion

PRIOR CONCURRENT THERAPY:

• No prior definitive therapy for prostate cancer, including prostatectomy, cryotherapy, or radiotherapy to the prostate or lower pelvis
• No more than 6 months of hormone ablation for gland downsizing