Aggressive prostate cancer risk may rise after vasectomy

Date: Jul-10-2014 In the largest and most comprehensive study of its kind, researchers from Harvard School of Public Health in Boston, MA, find that vasectomy is associated with a small increased risk of prostate cancer, and a larger increased risk for advanced or lethal prostate cancer.

Prostate cancer is a major cause of cancer-related deaths in men in the US, where vasectomy is

a common form of contraception, with around 15% of American men having the minor procedure, which

blocks the tubes that carry sperm from the testicles to the penis.

The researchers report their findings in the Journal of Clinical Oncology, where

they note that the link was still evident among men who had regular PSA tests, suggesting the

link with increased risk of lethal cancer cannot be due to diagnostic bias.

Co-author Lorelei Mucci, associate professor of epidemiology at Harvard School of Public

Health (HSPH), says:

"This study follows our initial publication on vasectomy and prostate cancer in 1993, with 19

additional years of follow-up and tenfold greater number of cases. The results support the

hypothesis that vasectomy is associated with an increased risk of advanced or lethal prostate

cancer."

For the study, Prof. Mucci and colleagues analyzed data on 49,405 American men who were

followed between 1986 and 2010 as participants of the Health Professionals Follow-up Study. The men were aged between 40 and 75

years at the start of the 24-year follow-up period.

In this study, 16 out of every 1,000 men developed lethal prostate cancer over 24 years of follow-up.

Over that time, 6,023 men were diagnosed with prostate cancer, including 811 who died of the

disease. One in four of the participants reported having undergone a vasectomy.

When they analyzed the data, the team found a 10% overall increased risk of prostate cancer in

those men who had a vasectomy.

However, further analysis found vasectomy was linked to a stronger increased risk of more

aggressive forms of prostate cancer: a 19% higher risk for advanced cancer and a 20% higher risk

of the lethal form.

And for a subgroup of men who were having regular PSA tests, the increased risk was 56%.

There was no significant link between vasectomy and risk of low-grade cancer.

Concerns have been raised before in connection with this type of study, that the links could

be a result of bias, but the researchers say their analyses took into account diverse information

that meant they could rule out potential biases. For example, one bias could be that men who have

vasectomies are more likely to seek medical care, or undergo more PSA tests. They also ruled out

bias due to the possibility of sexually transmitted infections.

It should be noted that the researchers are not suggesting in this study that simply

undergoing regular PSA screening can raise the risk of prostate cancer. There could be other

explanations for why the men having regular PSA screening showed the strongest raised risk for

prostate cancer. For instance, if an initial screening is positive, then regular screening is

recommended.

Relative risk does not mean absolute risk

Another point to note is that these numbers refer to relative risk - that is the extent to

which the underlying or absolute risk of developing the disease is affected. So, for example, if

a person's risk of getting a disease is 10%, then a relative risk of 10% means the absolute risk

is only 10% of 10%, or 11%.

In this study, 16 out of every 1,000 men developed lethal prostate cancer over 24 years of

follow-up. Thus, the result that vasectomy was linked to a 20% raised risk of lethal prostate

cancer, is relative to that 16 out of 1,000.

Therefore, as the researchers point out, although the 20% was found to be statistically significant

(that is unlikely due to chance), its effect is a relatively small increase in the absolute risk

of developing prostate cancer.

"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," says co-author Kathryn Wilson, a

research associate in HSPH's Department of Epidemiology.

Funds from the National Cancer Institute and the National Institutes of Health helped finance

the study.

Meanwhile, Medical News Today reported how a study led by the University of Adelaide

in Australia found that a test based on semen may be more accurate at

diagnosing prostate cancer. The researchers found that testing semen samples for small

molecules called microRNAs was "surprisingly accurate" at indicating which men had prostate

cancer and how severe it was.

Written by Catharine Paddock PhD

View all articles written by Catharine, or follow her on:

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.