At least 15 percent of American men have vasectomies, so when a study came out recently linking this common method of birth control to an increased risk of the most lethal kind of prostate cancer, it sparked some alarm in doctors' offices.
The findings "caused a lot of fear among many people, people who had had vasectomies," said Dr. Mohummad Minhaj Siddiqui, one of the study's authors and director of urologic robotic surgery and an assistant professor at the University of Maryland School of Medicine.
Siddiqui, who came Maryland from Harvard, said that although the study — the most comprehensive of its kind — made a more definitive connection than past research, he and other doctors caution that it shouldn't dissuade all men from having vasectomies.
Such aggressive cancer is still rare.
The study also didn't find that vasectomies caused a significant increase in risk of low-grade prostate cancer, which is diagnosed much more often. These cancers grow slowly and don't always cause health problems.
The American Urological Association doesn't recommend that doctors discuss the link with men who are considering a vasectomy, though officials are reviewing the study and may revise the guidelines, and some doctors say they already are talking about the study with patients.
Prostate cancer is the most common form of cancer among men, with more than 200,000 new cases annually, according to the U.S. Centers for Disease Control and Prevention. The study, doctors say, provides more information on what may increase a person's chances of cancer beyond advanced age and family history.
But they say additional research is needed to explain how vasectomies may be leading to the increased risk of lethal prostate cancer.
Past studies also found a link between the contraceptive procedure and the cancer, but some researchers theorized that more cases were found because men who had vasectomies sought more medical care. That was discounted by this study, which was led by researchers at the Harvard School of Public Health and published in the Journal of Clinical Oncology in July.
The study analyzed data from more than 49,000 men who were followed for up to 24 years. There were more than 6,000 cases of prostate cancer, including 811 lethal cases. A quarter of the men had vasectomies.
The study found that men with a vasectomy had about a 20 percent increased risk of lethal prostate cancer compared with those who did not have the procedure.
That led the study authors to conclude that doctors need to discuss the risk with patients.
"The decision to opt for a vasectomy as a form of birth control is a highly personal one, and a man should discuss the risks and benefits with his physician," said study co-author Kathryn Wilson, associate in Harvard's Department of Epidemiology, in a statement.
Siddiqui and others said they have been able to temper fears by explaining that the risk of lethal prostate cancer remain low.
"Because otherwise, people think, 'If I have a vasectomy, I'm going to die,' " Siddiqui said. "If that was the case, that would be a terrifying thing. That's not quite the story."
He said the rate of fatal prostate cancer was 16 in 1,000 for men who had not undergone vasectomies, and 19 in 1,000 for those who had.
Dr. Ballentine Carter, professor of urology and oncology at the Johns Hopkins School of Medicine, called the study "incredibly provocative."
But Carter, also a prostate cancer researcher, agreed that the study's findings should not necessarily alarm or dissuade someone who wants to have a vasectomy.
"While it isn't the type of study that would change policy, I would say it would urge or inform physicians that they need to tell patients about the findings before performing a vasectomy," said Carter, who does not perform vasectomies.
"The way I would frame this is there are studies that show a relationship between vasectomy and the development of cancer and there are studies that don't show a relationship between the two," said Carter. "We don't have a definitive answer to whether or not a vasectomy causes or is associated with a higher risk of lethal disease."
Dr. Bishoy Gayed, a urologic oncologist at Chesapeake Urology, agreed that more study is needed and said he would not tell his patients to reject a vasectomy based on the latest research.
It's a common and safe outpatient procedure, he said, though all surgery comes with risk. He already discusses potential outcomes with patients, and this issue should be added to that conversation.
He said screening patients for prostate cancer would also continue to be done on a per-patient basis. He said he would watch men with fathers and brothers with prostate cancer "like a hawk." Younger men, who make up the majority of vasectomy patients, still wouldn't generally be screened if they had no family history because the disease tends to strike older men.
"It's a good study, but I think the risk is still low," Gayed said. "It should be part of the overall discussion when we're counseling patients on vasectomies. It's not going to deter me from recommending a vasectomy, and it should not deter a patient from having a vasectomy"