Model predicts erectile function after prostate cancer

Researchers have developed a new model to predict the risk of erectile dysfunction for men undergoing prostate cancer treatment.

The model was developed using pre- and post-treatment data for more than 1,000 men who had prostatectomy, external radiotherapy or brachytherapy for prostate cancer at one of several academic medical centers between 2003 and 2006. The model's ability to predict erectile dysfunction two years after treatment was then validated in a community-based cohort of almost 2,000 men. The results were published in the Sept. 21 Journal of the American Medical Association.

Two years after treatment, post-treatment erections were reported by 37% of the overall patient group (95% CI, 34% to 40%) and 48% of the men who had functional erections before treatment (95% CI, 45% to 52%). Of those men who were potent before treatment, erectile dysfunction was reported posttreatment in 60% of the prostatectomy group (95% CI, 55% to 65%), 42% of the external radiotherapy group (95% CI, 33% to 51%) and 37% of the brachytherapy group (95% CI, 30% to 45%).

The researchers identified several factors in addition to the method of treatment that appeared to affect the rate of posttreatment dysfunction, including pretreatment function (measured by a sexual health-related quality-of-life score), age, serum prostate-specific antigen (PSA) level, race/ethnicity, and body mass index. The model's predictions of erectile function ranged from 10% to 70% depending on individual patient characteristics. The validation cohort indicated that the model performed well at predicting dysfunction.

The study also looked at the treatments men used to assist with erectile function. Phosphodiesterase-5 inhibitors were the most commonly used, and intracorporal penile injections were the least used but the most effective. Due to limitations of the observational design of the study, the results should be used not to determine treatment superiority, but rather to help set physicians' and patients' expectations after prostate cancer treatment, the authors said.

An accompanying editorial noted that the study was also limited by its failure to include men who chose watchful waiting over active surveillance and by the development of the model at academic medical centers, which may have better results.

After cautioning that the findings should be used cautiously, the editorialist offered a informal synopsis: “[F]or most scenarios, the take-away message is that if the patient has chosen surgery, he will more than likely lose erectile function, whereas if he has chosen radiotherapy, he has a better than even chance of preserving it, at least for 2 years.”