First author Dr. Matthew Resnick of Vanderbilt University Medical Center and colleagues tracked 1,655 men ages 55-74, of whom 70 percent had undergone prostatectomy -- prostate removal -- while 30 percent had undergone radiotherapy.
After five years both groups had a gradual decline in sexual function. At 15 years, erectile dysfunction was nearly universal, with 87 percent in the prostatectomy group and 93.9 percent in the radiotherapy group reporting sexual difficulties, Resnick said.
"At the two- and five-year time points, men who underwent prostatectomy were more likely to suffer from urinary incontinence and erectile dysfunction than men who received radiation therapy," Resnick said in a statement. "While treatment-related differences were significant in the early years following treatment, those differences became far less pronounced over time."
Nonetheless, patients in the surgery group were more likely to wear incontinence pads throughout the 15-year follow-up period.
"Regardless of the form of initial treatment, patients in this study had significant declines in sexual and urinary function over the duration of the study. The causes of these declines probably include advancing age and additional cancer therapies, in addition to the original therapy," said senior author Dr. David Penson, director of the Vanderbilt Center for Surgical Quality and Outcomes Research. "Patients need to be aware that all aggressive therapies for prostate cancer have significant side effects and perhaps these data make an argument for active surveillance -- avoiding aggressive treatment and closely following the cancer -- in certain cases."
Since the median life expectancy after treatment for prostate cancer is 13.8 years, the authors suggested the data might be used by physicians to counsel men who are considering treatment for localized disease, the study said.
The findings were published the New England Journal of Medicine.