Sildenafil Improves Sexual Function After Radiotherapy for Prostate Cancer

SAN FRANCISCO—Sildenafil (Viagra) is highly effective in improving erectile function in prostate cancer patients following three-dimensional (3D) conformal external radiotherapy, according to a study presented at the 43rd Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO abstract 248).

"Sildenafil is well tolerated, and it works well in reversing sexual dysfunction," said lead author Luca Incrocci, MD, PhD, of the Department of Radiation Oncology, University Hospital Rotterdam-Daniel den Hoed Cancer Center, Rotterdam, the Netherlands. "It should be the first line of treatment in men with prostate cancer who sustain sexual dysfunction after radiotherapy."

In this double-blind, placebo-controlled crossover study, 60 patients received either 50 mg of sildenafil or a placebo for the first 2 weeks of the study. The medications were taken 1 hour before sexual intercourse on demand but not more than once a day. After 2 weeks, the dose could be increased to 100 mg in case of unsatisfactory erectile response. At week 6, patients crossed over to placebo or sildenafil with the same study design as the first period.

Sexual data were collected using the International Index of Erectile Dysfunction (IIEF), a validated self-administered questionnaire, at baseline (4 weeks prior to treatment) and after 2 and 6 weeks of treatment. At the same time intervals, all patients completed a side effects questionnaire. Responses to the IIEF were graded on a scale of 1 (almost never or never) to 5 (almost always or always).

Patients who had treatment for prostate cancer from 1996 to 1998 were selected from medical records. The mean age of the patients was 68. All patients had complaints of erectile dysfunction, no evidence of metastases, were not on hormonal therapy or nitrates, and did not have a history of myocardial infarction.

Half of the patients had T1c-2a carcinoma and the other half had a T2b-3b tumors, with the majority having well or moderately differentiated disease.

All patients had completed radiation at least 6 months prior to the study, with a mean radiation dose of 66 Gy and a mean energy of 23 MV (range, 6 to 25).

The groups were well balanced in regards to age, tumor characteristics, and baseline sexual data. Patients were required to be in a stable relationship and to have sexual activity at least once a week.

For all but three of the questions on the IIEF, there was a significant increase in mean scores with sildenafil vs placebo. The only scores that did not increase significantly were those of intercourse and orgasm frequency and erection confidence, Dr. Incrocci said. "The total mean score of the IIEF was also much higher with sildenafil than with placebo," Dr. Incrocci said.

With sildenafil, 55% of patients were able to have successful intercourse vs 18% with placebo. The ability to get an erection, the ability to penetrate, and the maintenance of erection—long considered the most important signs of sexual function in men—increased significantly with sildenafil vs placebo. Baseline scores for these functions increased from 1.7, 1.5, and 1.4, respectively, to final scores for sildenafil of 2.9, 2.8, and 2.6, compared with 1.8, 1.6, and 1.5 for placebo.

Dr. Incrocci noted that most patients (90%) needed a dose adjustment after 2 weeks to a sildenafil dose of 100 mg.

In most patients, the medication was well tolerated, and side effects were mild or moderate, Dr. Incrocci said. Forty two percent of patients reported transient headache, 13% reported flushing, and 32% reported pyrosis after taking sildenafil. None of the patients discontinued the medication because of side effects.

"We can see from this study that sildenafil is an effective treatment, and the 100 mg dose is necessary after radiotherapy for prostate cancer," Dr. Incrocci said. "By using the 100 mg dose of sildenafil as first-line treatment, we can achieve the best results."

The study results were published in the December 2001 issue of the International Journal of Radiation Oncology, Biology and Physics (51:1190-1195, 2001).