Sildenafil is often used by men treated with radiation or radical prostatectomy for prostate cancer to achieve an erection sufficient for sexual intercourse, and it is effective to varying degrees when used on an as-needed basis. A randomized controlled trial has found that prophylactic daily use of sildenafil improved overall sexual function, as well as domains of sexual function, in prostate cancer patients undergoing radiation therapy.1 This is the first time a phase 3 study has demonstrated the effectiveness of prophylactic sildenafil in the setting of radiation.
“Prostate cancer patients treated with sildenafil and adjuvant radiation treatment had improved overall erectile function and overall satisfaction of their sexual activity and function. The most significant improvements were seen at 6 and 12 months after treatment, with a slight dip at the 24-month mark, suggesting that future trials need to be conducted to demonstrate if longer treatment duration can further improve outcomes,” said lead author Michael Zelefsky, MD, of Memorial Sloan-Kettering Cancer Center in New York City. No benefit for sildenafil was seen among a small group of 31 patients who were also treated with androgen deprivation therapy.
The prospective, randomized, double-blind, placebo-controlled trial included 295 patients with clinically localized prostate cancer who were treated with external beam radiation therapy and/or brachytherapy (permanent interstitial implantation of radioactive “seeds”). Patients were randomized in a 1:1 ratio to receive either daily sildenafil 50 mg or placebo. Treatment was initiated 3 days before radiation treatment and was continued daily for 6 months, when the drug was stopped. After that, sildenafil could be used as needed. Sexual function was assessed at 3-month intervals for the first year and thereafter at 18 and 24 months with the international index of erectile function (IIEF) and the international prostate symptom score (IPSS) questionnaires. At baseline, all patients had excellent erectile function, as assessed by IIEF.
Among 144 patients treated with radiation only who completed IIEF and IPSS questionnaires, overall sexual function was improved with daily sildenafil versus placebo at all time points. IIEF scores were 58.6 for sildenafil versus 49.4 for placebo at 6 months (P = .006); 56.3 versus 48.2, respectively, at 12 months (P = .02); and 54.9 versus 47.6, respectively, at 24 months (P = .04). Significant improvement in overall function, orgasmic function, sexual desire, intercourse satisfaction, and overall satisfaction were reported with sildenafil versus placebo. Overall IPSS was also significantly improved with sildenafil versus placebo (P <.001).
- Zelefsky MJ, Shasha D, Kollmeier M, et al. Results of a prospective randomized double-blind placebo-controlled trial evaluating the use of prophylactic sildenafil citrate during radiation therapy in the treatment of prostate cancer. Presented at: American Society for Radiation Oncology 54th Annual Meeting; October 29, 2012; Boston, MA. Abstract 3.