For the first time, a randomized controlled trial reported improved sexual function with 6 months of prophylactic sildenafil citrate before, during, and after radiation therapy in patients with prostate cancer.¹ The paper was presented at the Plenary Session during the 54th Annual Meeting of the American Society for Radiation Oncology (ASTRO).

Proof of Principle

“This trial demonstrates proof of principle that penile rehabilitation is important in the population of patients treated with radiotherapy. Prophylactic use of sildenafil improved overall erectile function and overall satisfaction with sexual activity and function,” said lead author Michael J. Zelefsky, MD, Memorial Sloan-Kettering Cancer Center, New York.

“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,” he continued.

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. At baseline, all patients had erectile function (International Index of Erectile Function [IIEF] score > 17 on the erectile function domain).

Study Design and Results

Patients were randomly assigned in a 2:1 ratio to receive either sildenafil at 50 mg daily or placebo. Treatment was initiated 3 days before radiation treatment and continued daily for 6 months, when the drug was stopped. After that, sildenafil could be used on an as-needed basis. Thirty-one patients were also treated with 6 months of androgen-deprivation therapy.

Sexual function was assessed at 3-month intervals for the first year, and thereafter at 18 and 24 months with the IIEF, and for urinary function, the International Prostate Symptom Score (IPSS) questionnaires. No benefit for prophylactic use of sildenafil was observed among the 31 patients who received androgen-deprivation therapy, and this group of patients was excluded from the analysis.

Among 142 patients who completed these questionnaires and completed radiation therapy, overall sexual function was significantly improved with daily sildenafil vs placebo at all time points. IIEF scores were 58.6 for sildenafil vs 49.4 for placebo, respectively, at 6 months (P = .006); 56.3 vs 48.2 at 12 months (P = .02); and 54.9 vs 47.6 at 24 months (P = .04). Significant improvement in overall satisfaction and erectile function were observed with sildenafil vs placebo. Overall IPSS scores were also significantly improved with sildenafil vs placebo (P < .001).

A multivariate logistic regression analysis controlled for age and baseline IIEF scores found that sildenafil significantly improved sexual satisfaction and IIEF scores. ■

Disclosure:Dr. Zelefsky stated that Pfizer provided the drug for the study and provided limited funding for research assistance.

Reference

1. Zelefsky MJ, Shasha D, Kollmeier M, et al: Results of a prospective randomized double-blind placebo trial evaluating the use of prophylactic sildenafil citrate during radiation therapy in the treatment of prostate cancer. 54th ASTRO Annual Meeting. Abstract 3. Presented October 29, 2012.