Doctors in Boston have improved prediction of which men will regain sexual functioning after prostate cancer treatment.

A study published Tuesday in The Journal of the American Medical Association by researchers from the Dana-Farber/Harvard Cancer Center, the world’s largest cancer center, and the Prostate Center at Beth Israel Deaconess Medical Center, compared outcomes for different kinds of treatment.

The predictors for erectile function in the prostatectomy (prostate removal) group were age and prostate specific antigen level.

The predictor in the radiation therapy group was whether or not the patient has undergone hormone therapy. Those who did not get hormone therapy were more likely to regain erectile function.

Age and body weight determined recovery of erectile function in the group that had brachytherapy, the insertion of a small radiation source in the organ.

This year, about 90,000 American men will undergo radical prostatectomy, a procedure in which the entire prostate is removed. They face common side effects such as impotence and incontinence during routine activities, and urologists have recently learned that some may also leak urine during sex.

According to the American Cancer Society, one in six men will develop prostate cancer at some point in his life, and one in 36 will die of it. Most prostate cancers are slow-growing, but some are aggressive.

An important part of evaluating prostate cancer is determining how far it has spread. Knowing the stage helps define prognosis and is useful when selecting therapies.