Tadalafil in Preventing Erectile Dysfunction in Patients With Prostate Cancer Treated With Radiation Therapy

Inclusion Criteria

• Clinical stage T1b-T2b (AJCC, 6th ed.) adenocarcinoma of the prostate within 6 months of registration
• Clinically negative lymph nodes as established by imaging (pelvic ± abdominal CT or MR), nodal sampling, or dissection within 3 months prior to registration. Patients with lymph nodes equivocal or questionable by imaging are eligible if the nodes are ≤ 1.5 cm. Lymph node assessment is optional, and at investigator discretion, for patients with Gleason Score 0), other than localized basal cell or squamous cell skin carcinoma (AJCC Stage 0-II), or a hematological malignancy (e.g., leukemia, lymphoma, myeloma) unless continually disease free for at least 5 years
• History of myocardial infarction within the last year
• Heart failure in the last 6 months
• Uncontrolled arrhythmias, hypotension ( 170/100 mm Hg)
• Stroke within the last 6 months
• Use of luteinizing hormone-releasing hormone (LHRH) agonist androgen suppression (e.g., Lupron, Zoladex), anti-androgen (e.g., Casodex, Eulexin, Nilandron), or estrogenic (e.g., diethylstilbestrol) agents within the last 6 months
• Current use of any organic nitrate or as needed nitrates (e.g., use of nitroglycerin)
• Current use of cimetidine, ketoconazole, itraconazole, erythromycin, or ritonavir
• Known moderate to severe renal insufficiency or end-stage renal disease
• Known severe hepatic impairment
• Use of mechanical (vacuum) devices, intracorporeal, intraurethral, topical, or oral (sildenafil, tadalafil, vardenafil) agents as therapy for ED or supplements to enhance sexual function within 5-7 days prior to the start of RT. Patients who discontinue these therapies remain eligible if they can meet eligibility criteria
• Pretreatment (before starting prostate cancer treatment) ED as measured by IIEF Question 1, "How often were you able to get an erection during sexual activity?" - with responses of:
• "no sexual activity" [response 0] or
• "almost never/never" [response 1] or
• "a few times (much less than half the time)" [response 2]
• Prior penile implant or history of bilateral orchiectomy
• Prior prostatectomy, prostatic cryosurgery or high-intensity focused ultrasound (HIFU), radionuclide prostate brachytherapy, or chemotherapy for prostate cancer
• Prior or anticipated combined external RT and brachytherapy
• Prior or anticipated external RT to the pelvic ± para-aortic lymph nodes
• Acquired Immune Deficiency Syndrome (AIDS) based upon current Centers for Disease Control and Prevention (CDC) definition; note, however, that HIV testing is not required for entry into this protocol. The need to exclude patients with AIDS from this protocol is necessary because the treatments involved in this protocol may be significantly immunosuppressive. Protocol-specific requirements may also exclude immunocompromised patients.
• Anatomical genital abnormalities or concurrent conditions that in the estimation of the physician would prohibit sexual intercourse or prevent study completion
• Major medical or psychiatric illness which, in the opinion of the investigator, would prevent completion of treatment or would interfere with follow-up