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Sildenafil citrate (Viagra) and erectile dysfunction following external beam radiotherapy for prostate cancer: a randomized, double-blind, placebo-controlled, cross-over study

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Abstract

Purpose: To determine the efficacy of sildenafil citrate (Viagra) in patients with erectile dysfunction after three-dimensional conformal external beam radiotherapy (3D-CRT) for prostate cancer.

Methods and Materials: 406 patients with complaints of erectile dysfunction and who completed radiation at least 6 months before the study were approached by mail. 3D-CRT had been delivered (mean dose 68 Gy). Sixty patients were included and entered a double-blind, placebo-controlled, cross-over study lasting 12 weeks. They received during 2 weeks 50 mg of sildenafil or placebo; at Week 2 the dose was increased to 100 mg in case of unsatisfactory erectile response. At Week 6, patients crossed over to the alternative treatment. Data were collected using the International Index of Erectile Function (IIEF) questionnaire, and side effects were recorded.

Results: Mean age was 68 years. All patients completed the study. For most questions of the IIEF questionnaire there was a significant increase in mean scores from baseline with sildenafil, but not with placebo. Ninety percent of the patients needed a dose adjustment to 100 mg sildenafil. Side effects were mild or moderate.

Conclusion: Sildenafil is well tolerated and effective in improving erectile function of patients with ED after 3D-CRT for prostate cancer.

Introduction

Prostate cancer (PC) has become the most frequent nonskin male malignancy in Western countries. Over recent years the number of PC-diagnosed patients has dramatically increased because of routine prostate-specific antigen (PSA) testing, though erectile dysfunction (ED) after radiation for PC is becoming a concern. Published rates of ED following external beam radiotherapy (ERT) vary from 7% to 64% 1, 2, 3. In noncontrolled studies, sildenafil citrate (Viagra) has been reported to be effective in up to 77% of patients 2 years or longer after ERT 4, 5, 6, 7. We performed a randomized, double-blind, placebo-controlled, cross-over study to evaluate the efficacy of sildenafil citrate in treating ED in patients who had received three-dimensional conformal external beam radiation (3D-CRT) for PC.

Section snippets

Methods and materials

The medical records of subjects treated with 3D-CRT for PC in the period 1996–1999 were reviewed. A letter in which a study was announced to treat ED with sildenafil was sent to 406 patients with no sign of metastases, no postradiotherapy rise in PSA, who were not on hormonal therapy, who were not using nitrates, with no history of myocardial infarction or cerebral vascular accident and with no prior radical prostatectomy. Eighty-two patients showed interest in the study. After reviewing the

Results

All patients completed the study. Mean time between completion of radiation treatment and initiation of the study was 39 (range 15–55) months. Both treatment sequences were well balanced regarding all baseline scores of the IIEF (all p values > 0.36). Also distribution of time from completion of radiation was the same. A comparison of mean scores of the IIEF questions before and after 6 weeks of treatment with sildenafil or placebo is reported in Table 2.

For all items of the IIEF questionnaire

Discussion

Sildenafil citrate (Viagra) is a selective inhibitor of cyclic guanosine monophosphate (cGMP) specific phosphodiesterase type 5, and hence inhibits the degradation of cGMP in the cavernosal smooth-muscle cells, restoring erectile response to sexual stimulation in patients with ED of different etiologies 9, 10. To our knowledge, no randomized, placebo-controlled, double-blind trials have been performed to assess the efficacy of sildenafil to treat ED after radiotherapy for PC. Previous,

Conclusions

Sildenafil citrate (Viagra) is an effective and well tolerated oral treatment in men with ED after 3D-CRT for prostate cancer. In the present study, side effects were mild or moderate and never led to discontinuation of the drug. Because of the simplicity of delivery and the acceptable side effects, sildenafil should be the first treatment option for patients complaining of erectile dysfunction following radiotherapy for prostate carcinoma, but not using nitrates.

Acknowledgements

To Mrs L. Bakri, medical student, for collecting the data and to G. Dohle, M.D., urologist, for his comments on the study protocol.

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This study has been supported by an unrestricted grant from Pfizer B.V., The Netherlands.

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