Prostate Cancer and Vasectomy Not Linked…But With One Caveat

Roxanne Nelson, BSN, RN

March 16, 2017

The findings to date have been confusing and conflicting: Does vasectomy put a man at risk for subsequent prostate cancer?

The answer largely depends on the study. Some say yes, while others say no.

The latest data, from a large European prospective study, shows no elevated risk for overall, high-grade, or advanced-stage prostate cancer or death due to the disease in men who had undergone vasectomy.

In a study that included almost 4400 men with prostate cancer, including 641 who had had vasectomy, the procedure was not associated with prostate cancer risk after an average of 15 years of follow-up (hazard ratio [HR], 1.05).

The one caveat, however, was a small increase in the risk for low-intermediate–grade prostate cancer in men who had a vasectomy (HR, 1.14). However, the authors note that this increase may well be due to differences in health-monitoring behaviors.

The study was published online March 6 in the Journal of Clinical Oncology.

What Does the Evidence Say?

In an accompanying editorial, Meir Stampfer, MD, DrPH, professor of medicine, Harvard Medical School, Boston, Massachusetts, and colleagues note that the current findings contribute to a growing body of literature that has examined a potential relationship between vasectomy and prostate cancer.

The evidence is conflicting, they point out, with several studies finding no association and others showing a small to moderately elevated risk.

Dr Stampfer and his colleagues briefly review the current literature and point out that detection bias in some of these studies could obscure "a true association with advanced or fatal disease if tumors among men with vasectomy tend to be detected and treated earlier compared with men without vasectomy."

They also looked at whether "effect modification" or different types of exposure and definitions of outcome could also help explain the contradictory results, but there was no evidence of either. However, they note a suggestion that the age at vasectomy could play a role because there is a stronger association for vasectomy at a younger age.

A third point the editorialist make is that any potential association must be considered in a public health context. One study observed a relative risk of 1.19 for lethal prostate cancer in the Health Professionals Follow-Up Study cohort and a 1.56 increase in a highly screened subpopulation (J Clin Oncol. 2014;32:3033-3038).

Given the 2.6% absolute risk of dying of prostate cancer in the United States, the editorialists point out, the small magnitude of the association reported in that study extrapolates to only a small increase in absolute risk.

As for the latest study, Dr Stampfer told Medscape Medical News that the "current data are not sufficient to rule out a small increase in risk of lethal prostate cancer due to vasectomy."

I believe this should not be a factor is deciding about vasectomy. Dr Meir Stampfer

"However, a large risk can be ruled out with confidence," he said. "Since the absolute increase in risk, if any, is modest at most, I believe this should not be a factor is deciding about vasectomy."

Study Details

In the current study, Karl Smith Byrne, MPhil, from the Cancer Epidemiology Unit, University of Oxford, United Kingdom, and colleagues, investigated the association of vasectomy with prostate cancer using the cohort from the European Prospective Investigation into Cancer and Nutrition (EPIC).

The study included 84,753 men aged 35 to 79 years, with 15% reporting that they had undergone a vasectomy.

The authors did not find a significant association between vasectomy and prostate cancer risk, and the results remained unaltered (HR, 1.05; 95% CI, 0.96 - 1.15) after adjustment for confounders, including body mass index, smoking status, marital status, level of education, alcohol consumption, physical activity, and protein from dairy sources.

There was no evidence of heterogeneity by disease stage, but there was evidence of heterogeneity by tumor grade (P = .02). An association was observed between vasectomy and an increased risk for low-intermediate–grade prostate cancer (HR, 1.14; 95% CI, 1.01 - 1.29) but not high-grade disease (HR, 0.83; 95% CI, 0.64 - 1.07).

No significant associations were observed with prostate cancer–related mortality (HR, 0.88; 95% CI, 0.68 - 1.12).

The authors point out that the significantly increased risk for low-intermediate–grade prostate cancer seen in this study "might be at least partly explained by differences in the use of PSA testing."

There was also an association with age, seen between prostate cancer and vasectomy. Compared with men who had not had undergone the procedure, those who did so when they were younger than the median age were at a significantly increased risk for prostate cancer (HR, 1.18; 95% CI, 1.03 - 1.35).

Conversely, no significant association was observed among men who were older than the median age when they underwent the procedure (HR, 0.99; 95% CI, 0.89 - 1.09).

Funded by Cancer Research UK and the Clarendon Fund, University of Oxford. The study authors have disclosed no relevant financial relationships. Dr Stampfer reports a relationship with Elysium Health; none of the other editorialists have disclosures.

J Clin Oncol. Published online March 6, 2017. Abstract, Editorial

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