This study followed patients for one year after they received treatment for prostate cancer.
The results of this study showed no significant difference between tadalafil and a placebo (mock medication) in improving ED after radiation treatment for prostate cancer.
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This study was led by Thomas M. Pisansky, MD, of the Mayo Clinic in Rochester, Minn.
The research team randomly assigned 242 men who started radiation therapy for prostate cancer to either a daily 5-mg dose of tadalafil or a placebo (mock medication) for 24 weeks.
These patients were recruited from 76 sites across the United States and Canada from November 2009 to February 2012, with follow-up continuing until March 2013.
Dr. Pisansky and team set out to determine if tadalafil was effective at preserving erectile function in patients who received radiation therapy for prostate cancer.
Radiation therapy uses high-energy radiation to kill cancer cells.
The research team evaluated the participants between weeks 28 and 30 as well as at one year.
The data from the first evaluation that took place between weeks 28 and 30 showed no statistical difference in levels of ED between men who received tadalafil and those who received the placebo (79 percent compared with 74 percent reporting no ED).
The follow-up at one year showed similar numbers and no statistically significant difference, with 72 percent of the tadalafil group reporting normal erectile function, compared with 71 percent of the placebo group.
The researchers found that 59 percent of the tadalafil group reported mild or moderate adverse effects of either the medication or radiotherapy, while 52 percent of the placebo group reported the same.
Dr. Pisansky and colleagues concluded that there was no evidence that the daily use of tadalafil in conjunction with radiotherapy for prostate cancer was effective at improving ED compared to a placebo.
This study was limited by the testing of only one dose and frequency of dosing.
This study was first published April 2 in JAMA.
The research was funded by the National Cancer Institute and Eli Lilly & Co, the manufacturer of Cialis.
Some of the study's authors reported receiving consultations and lecture fees as well as royalties from companies such as Bristol-Myers Squibb, General Electric Healthcare and others.