The largest and longest study ever to look at the persistent notion that vasectomy might promote prostate cancer has found that the sterilization procedure does not increase the chance of developing or dying of the disease.

For the new report, American Cancer Society researchers analyzed prostate cancer cases and deaths among 42,000 U.S. men who underwent a vasectomy, and 321,000  men who did not. The men were followed from 1982 to 2012 as part of a much bigger, ongoing cancer society study designed to assess risk factors for all types of cancer.

After controlling for issues such as age and smoking status, the overall incidence of prostate cancer, the incidence of aggressive prostate cancers, and death rates were the same among the groups, regardless of sterilization status.

"No one study is going to be enough to completely rule out a link," said cancer society epidemiologist Eric Jacobs, lead author of the paper, published Monday in the Journal of Clinical Oncology. "But if it were me, I wouldn't be worried."

An estimated 15 percent of men in the United States have had a vasectomy, a procedure that cuts or blocks the tubes that transport sperm,  so concern about safety is understandable.  Still, the method has been suspected -- and exonerated -- of a surprisingly long list of health problems, including heart disease, testicular cancer, even dementia.

Interest in a possible prostate cancer connection has waxed and waned over the last 30 years, with some scientists speculating that vasectomy causes inflammation or hormonal changes that could somehow induce or spur cancer. Most experts consider it a medical myth that just won't die, like the ones linking underwire bras or deodorants to breast cancer.

"The consensus is that there is no plausible biological explanation" for a link with cancer, Jacobs said.

"If men want to reduce their risk of fatal prostate cancer, they should quit smoking and maintain a healthy weight. Obesity and smoking have both been consistently linked with a higher risk of developing fatal prostate cancer," he said.

The evidence linking sterilization and cancer has been so weak and inconsistent that  last year, the American Urological Association asserted in its guidelines that vasectomy is not a risk factor for the malignancy and doctors don't need to mention it during pre-vasectomy counseling.

The urologists' group was not fazed by a 2014 Harvard analysis of data from  49,000 men in health professions, including  12,300 with vasectomies, who were followed for 24 years. That study, the largest up to that point, linked the procedure to a slight -- 20 percent -- increase in the risk of lethal cancer, but not low-grade cancers.

"It wasn't an enormous increase in risk, but if it were true, it's something men should consider," Jacobs said. "That's why we undertook this study."

Tobias S. Kohler, a urology professor at Southern Illinois University School of Medicine in Springfield, recently published a review of studies that looked, mostly in vain, for a link. He praised the new analysis.

"Vasectomy is the safest, most effective form of birth control we have, for both men and women  -- which is good for humanity," Kohler said. "I'm just glad to see another well-done paper that shows no risk of prostate cancer."