Intensity-Modulated Radiation Therapy With or Without Decreased Radiation Dose to Erectile Tissue in Treating Patients With Stage II Prostate Cancer

RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Intensity-modulated radiation therapy (radiation directed at the tumor more precisely than in standard radiation therapy) may reduce damage to healthy tissue near the tumor. It is not yet known whether reducing the dose of radiation to erectile tissue will help prevent erectile dysfunction.

PURPOSE: This randomized phase III trial is studying intensity-modulated radiation therapy alone to see how well it works compared to intensity-modulated radiation therapy with reduced doses to erectile tissue in treating patients with stage II prostate cancer.

OBJECTIVES:

Primary

* Compare erectile dysfunction in patients with stage T1b-T2c adenocarcinoma of the prostate after treatment with intensity-modulated radiotherapy with vs without dose sparing for erectile tissue.

Secondary

* Compare biochemical freedom from failure rates, as a measure of prostate cancer control, in patients treated with these regimens.
* Compare the quality of life of patients treated with these regimens.
* Determine the association of molecular markers and biochemical freedom from failure rate and other endpoints in patients treated with these regimens.

OUTLINE: This is a randomized, single-blind study. Patients are stratified according to age (≤ 65 vs \> 65), prescription radiotherapy dose (74 Gy vs 76 Gy), and frequency of erection during sexual activity within the past 4 weeks (a few times vs sometimes vs most times to always). Patients are randomized to 1 of 2 treatment arms.

* Arm I: Patients undergo conventional intensity-modulated radiotherapy (IMRT) once daily 5 days a week for approximately 7.5 weeks.
* Arm II: Patients undergo IMRT with dose restriction to erectile tissue once daily 5 days a week for approximately 7.5 weeks.

Treatment in both arms continues in the absence of unacceptable toxicity or disease metastasis.

Quality of life is assessed at baseline, at 6 and 12 months, and then annually for 4 years

Patients are followed at 3 months and then every 6 months thereafter.

PROJECTED ACCRUAL: A total of 200 patients (100 per treatment arm) will be accrued for this study within 2.5 years.

Eligibility Criteria:
DISEASE CHARACTERISTICS:

* Histologically confirmed adenocarcinoma of the prostate

  * Clinical stage T1b-T2c by palpation
* Pretreatment prostate-specific antigen ≤ 20 ng/mL
* Gleason score ≤ 7
* Suitable erectile function, defined as a response ≥ score 2 in question #1 of the International Index of Erectile Function Questionnaire
* No clinical, radiographic, or pathologic evidence of nodal or distant metastatic disease

PATIENT CHARACTERISTICS:

Age

* Not specified

Performance status

* Zubrod 0-1

Life expectancy

* Not specified

Hematopoietic

* Not specified

Hepatic

* Not specified

Renal

* Not specified

Other

* Fertile patients must use effective contraception
* No other active malignancy within the past 5 years except nonmetastatic skin cancer or early-stage chronic lymphocytic leukemia (well-differentiated small cell lymphocytic lymphoma)
* No other medical condition that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

* Not specified

Chemotherapy

* Not specified

Endocrine therapy

* Prior androgen-ablation therapy allowed provided total calculated duration ≤ 4 months

Radiotherapy

* No prior pelvic radiotherapy

Surgery

* No prior or planned radical prostate surgery