RATIONALE: Sildenafil may be effective in helping patients who have undergone treatment for prostate cancer to have an erection for sexual activity and may improve sexual satisfaction and quality of life.

PURPOSE: Randomized clinical trial to study the effectiveness of sildenafil in treating erectile dysfunction in patients who have undergone radiation therapy and hormone therapy for prostate cancer in clinical trial RTOG-9910.

OBJECTIVES:

• Compare the effect of sildenafil vs placebo on erectile dysfunction in patients with prostate cancer treated with radiotherapy and antiandrogens on RTOG-9910.
• Compare the overall sexual function and satisfaction of patients treated with these regimens.
• Compare sexual satisfaction of partners of patients treated with these regimens.
• Compare patient and partner marital adjustment after treatment with these regimens.
• Determine factors that may predict response to sildenafil, including age, pretreatment sexual function, tobacco use, and comorbidities in these patients.

OUTLINE: This is a randomized, placebo-controlled, multicenter study. Patients are stratified according to prior use of sildenafil after treatment on RTOG-9910 and level of response (No vs yes [unsatisfactory] vs yes [satisfactory]), International Index of Erectile Function (IIEF) Question #1 score (0-1 vs 2-3), and RTOG-9910 treatment arm (I vs II). Patients are randomized to 1 of 2 treatment arms.

• Arm I: Patients receive oral sildenafil 1 hour prior to desired sexual intercourse.
• Arm II: Patients receive oral placebo 1 hour prior to desired sexual intercourse.

Treatment on both arms continues for 12 weeks. Patients then cross over to treatment on the other arm for 12 weeks.

Quality of life, including sexual function, marital adjustment, and partner's satisfaction, is assessed at baseline, at 12 and 25 weeks, and at 1 year.

Patients are followed at 1 year.

PROJECTED ACCRUAL: A total of 332 patients (166 per treatment arm) will be accrued for this study.

DISEASE CHARACTERISTICS:

• Prior treatment on RTOG-9910 for intermediate relapse-risk stage II or III prostate cancer as determined by any of the following combinations of factors:

  • T1b-4, Gleason score 2-6, and prostate-specific antigen (PSA) greater than 10 ng/mL but no greater than 100 ng/mL
  • T1b-4, Gleason score 7, and PSA less than 20 ng/mL
  • T1b-1c, Gleason score 8-10, and PSA less than 20 ng/mL

• Radiotherapy completed within the past 6 months to 5 years

• Pretreatment (before enrollment on this study) erectile dysfunction as measured by International Index of Erectile Function Question #1

  • Erectile dysfunction before starting prostate cancer therapy allowed

• Patients without partners or without partners willing to participate allowed

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• Zubrod 0-2

Life expectancy

• Not specified

Hematopoietic

• Not specified

Hepatic

• Not specified

Renal

• Not specified

Cardiovascular

• No myocardial infarction within the past year

Other

• No other invasive cancer within the past 5 years except localized basal cell or squamous cell skin cancer (stage 0-II)
• No anatomical genital abnormalities or concurrent conditions that would prohibit sexual intercourse or preclude study participation
• No other major medical or psychiatric illness that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• Not specified

Endocrine therapy

• More than 6 months since prior androgen suppression (e.g., leuprolide or goserelin), antiandrogen (e.g., bicalutamide, flutamide, or nilutamide), or estrogenic (e.g., diethylstilbestrol) agents

Radiotherapy

• See Disease Characteristics

Surgery

• No prior penile implant
• No prior bilateral orchiectomy

Other

• No concurrent sildenafil
• No concurrent participation in another medical research study to treat prostate cancer
• No concurrent organic nitrate or requirement for nitrates (e.g., nitroglycerin as needed)
• No concurrent ketoconazole, itraconazole, or erythromycin
• No concurrent use of mechanical (vacuum) devices or intracorporeal, intraurethral, topical, or oral agents for erectile dysfunction