Methodology:
Thomas M. Pisansky, M.D., of the Mayo Clinic, Rochester, Minn., and colleagues with theRadiation Therapy Oncology Group, randomly assigned 242 men with prostate cancer to receive tadalafil (5 mg) or placebo daily for 24 weeks starting with radiation therapy (either with external radiotherapy [63 percent] or brachytherapy [37 percent]). The study was conducted at 76 sites in the United States and Canada; participants were recruited between November 2009 and February 2012, with follow-up through March 2013.