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Early Response Predicts Long Term Durability of Sildenafil (Viagra) for Erectile Dysfunction after Radiation Therapy: Presented at ASTRO

By Peggy Peck

SALT LAKE CITY, UT -- October 22, 2003 -- Sildenafil citrate (Viagra) is an effective long-term treatment for radiation therapy-associated erectile dysfunction, according to results presented here October 20^th at the 45^th Annual Meeting of the American Society for Therapeutic Radiology and Oncology.

Michael Zelefsky, MD, of Memorial Sloan-Kettering Cancer Center, New York, said about 70% of men who develop ED after radiation therapy respond to sildenafil. "Results of this study suggest that response is durable," he said.

Dr. Zelefsky and colleagues followed 363 men who underwent either 3-dimensional conformal radiation therapy (3D-CRT) at a median dose of 81Gy or brachytherapy for treatment of clinically localised prostate cancer. All men were potent prior to treatment. Men who developed ED following treatment were prescribed sildenafil 50 to 100mg.

Results were a surprise to the researchers, Dr. Zelefsky said. "I didn't really expect them to still be taking [sildenafil] and I expected that for many men the effect would diminish with time."

Initially 75% of men responded to sildenafil treatment. After an average of 3.7 years (range 4-45 months), 96% of the men who initially responded to Viagra were still taking the drug and all but 2% of the men said the drug was still effective.

Dr. Zelefsky said the men who reported that sildenafil stopped working were those who were treated with extremely high dose 3D-CRT. He said the efficacy dropped to 72% for men who receive 75.6 Gy or higher, while 85% of men who received lower dose radiation said the drug worked. "There was no dose-dependent difference in response for men who were treated with brachytherapy," he said.


[Study title: Prognostic Factors for Maintained Efficacy of Sildenafil Citrate in the Management of Erectile Dysfunction After Radiotherapy for Prostate Cancer. Abstract 1021]

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