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.

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 of the studies. 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, Tennessee. He helped prepare patients’ questionnaires used in Barocas’ study.

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Conwill said the diagnosis put him “in shock mode,” and hearing doctors talk about cancer stage, tumor size, treatment options and potential side effects was like a foreign language. He wondered, “’How does that apply to me?’ How in the world do I make this decision?’”

The studies help provide answers, showing quality of life outcomes depends on treatment but also on men’s sexual and urinary function before diagnosis.

Conwill knew impotence was possible -- but when it happened, “it was devastating -- it still is devastating,” said Conwill, who has been married for 52 years. Still, he doesn’t regret surgery because he’s confident he won’t face cancer again.

Both U.S. studies were published Tuesday in the Journal of the American Medical Association. A journal editorial says with these new results, men with early prostate cancer “have never been better informed about the trade-off they have to make.”

More than 1 million men worldwide are diagnosed with prostate cancer each year, most in developed countries. The American Cancer Society estimates that there will be about 160,000 new U.S. cases and more than 26,000 deaths this year.

Patients in both studies who opted for treatment had newer kinds, mostly robotic surgery with small incisions to remove the prostate or external precision radiation that helps spare surrounding tissue. In one study, led by Dr. Ronald Chen at the University of North Carolina, some men got a type of radiation that implants radioactive pellets into the tumor.

“No study to date has compared the quality of life outcomes of these (newer) options,” Chen said.

The results mostly echo the side effects from older options: persistent impotence and incontinence were more common after surgery, and both types of radiation caused more short-term urinary problems. Also, men who had external radiation reported more short-term bowel problems.

Treatment-related differences in quality of life lessened during the studies. That’s partly because cause quality of life tends to worsen with age in all men including those who chose observation.

The studies involved a total of almost 3,700 men, in their 60s on average at diagnosis. They filled out questionnaires periodically over two to three years. That’s not long enough to compare recurrence or survival rates, so the focus was on men’s lingering symptoms.

Results included:

-Among men who had normal sexual function before treatment in the Chen study, poor sexual function was reported by more than 57 percent of surgery patients two years later, versus 34 percent of those who had radiation implants, 27 percent who had external radiation and 25 percent who chose observation.

-Three years after treatment in the Barocas study, 14 percent of surgery patients said urinary incontinence was a significant problem, versus 6 percent of men who chose observation and 5 percent of radiation patients.