CHICAGO — Men with early-stage prostate cancer face a dizzying quandary over which treatment to choose, but two new studies on side effects may make those decisions a bit easier.

The research bolsters evidence that sexual problems and urinary incontinence are more common after surgery than after radiation or ‘‘watchful waiting’’ without treatment.

But it also shows differences in quality of life tend to wane with time for those with prostate cancer that hasn’t spread — the type that affects most men with the disease.

Both US studies were published Tuesday in the Journal of the American Medical Association.

Given earlier research showing comparable survival rates, the results also support observation as a reasonable option for men with early disease, especially those with less aggressive tumors, said Dr. Daniel Barocas of Vanderbilt University, leader of one study.

Still, he noted, men who choose observation could have problems related to enlarged prostates, including frequent urination, that those who have surgery don’t face.

The research provides a road map to help guide patients’ choices, ‘‘and that takes a lot of the terror out of the decision-making,’’ said prostate cancer survivor Ralph Conwill of Nashville. He helped prepare patients’ questionnaires used in Barocas’s study.

The studies showed that quality of life outcomes depend on treatment but also on men’s sexual and urinary function before diagnosis.

A journal editorial said that with these new results, men with early prostate cancer ‘‘have never been better informed about the trade-off they have to make.’’

Associated Press