By Lisa Rapaport

(Reuters Health) - Having a vasectomy doesn't increase a man's risk of developing prostate cancer or dying from it, a Canadian study suggests.

Previous research has been mixed about the risk of prostate cancer associated with vasectomy, a common form of long-term birth control that involves snipping or blocking tubes that transport sperm out of the testicles.

“Our study involving a large number of individuals followed for many years found no increased prostate cancer risk,” said lead study author Madhur Nayan, a researcher at the University of Toronto.

“We were able to control for some of the differences between men undergoing vasectomy and those not (e.g. visits to a physician) - these differences could have explained why in other studies men undergoing vasectomy were found to be at increased risk for prostate cancer,” Nayan added by email. “We feel our findings reflect an accurate assessment of the risk of prostate cancer after vasectomy.”

Prostate cancer is the second most common type of malignancy among men in the U.S., behind melanoma.

While vasectomy isn’t the primary form of birth control for most couples in the U.S., it’s estimated that 1 percent of men aged 25 to 49 have the procedure each year, adding up to around 500,000 vasectomies annually, according to a 2012 research review.

Men who undergo this sterilization procedure often worry about whether it will negatively impact their sex life or fail to prevent pregnancy.

Concerns about a cancer risk spiked after a large 2014 study linked vasectomies to a 10 percent greater risk of developing prostate tumors, as well as a 20 percent higher risk of fatal prostate cancer, Nayan and colleagues note in The BMJ.

But the overall risk of prostate cancer is still quite low, said Jennifer Rider, a public health researcher at Boston University and Harvard University who was an author on the 2014 study.

“Even if there is an increased risk of prostate cancer associated with vasectomy, it is likely restricted to aggressive prostate cancer, which is relatively rare, and the increased risk is very modest,” Rider said by email. “The benefits of vasectomy for an individual man may often outweigh these risks.”

For the current study, researchers examined data on 326,607 men aged 20 to 65 who underwent a vasectomy and compared them to men with similar age and health status who didn’t have this procedure.

Researchers followed half of the men for at least 10.9 years.

During the study period 1,843 men in the vasectomy group and 1,619 men in the control group developed prostate cancer, the study found.

Fifty men died from prostate cancer by the end of the study.

Overall, men with vasectomies were about 5 percent more likely to have lethal “high-grade” prostate cancer, 4 percent more likely to have advanced tumors, and 6 percent more likely to die – but all of these differences were too small to rule out that they were due to random chance.

One limitation of the study was that researchers lacked data on what type of prostate cancer screening tests men underwent, which might influence the odds of a diagnosis, the authors note. The study also didn’t have data on certain factors that influence the risk of prostate cancer such as family history, ethnicity, eating habits, and ejaculation frequency, the researchers also point out.

Even so, men shouldn’t be deterred from vasectomies out of concern about the risk of developing prostate cancer, the authors conclude.

SOURCE: http://bit.ly/2eWqKhg BMJ, online November 3, 2016.