September 19, 2016
2 min read

Vasectomy does not increase risk for prostate cancer incidence, mortality

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Men who underwent vasectomy did not demonstrate an increased risk for prostate cancer incidence or mortality, according to an analysis of large prospective cohorts published in Journal of Clinical Oncology.

Previous data on this association have been mixed and limited. Of six prospective studies published before 2014, three showed a statistically significant positive association between vasectomy and prostate cancer; the other three did not.

However, an updated analysis of the Health Professionals Follow-up Study published in 2014 showed vasectomy lead to a 10% increased risk for prostate cancer and a 20% greater risk for high-grade and lethal prostate cancer.

“Although a previous study suggested an association, our results show no connection between vasectomies and overall risk for prostate cancer, or of dying of prostate cancer, and should provide some reassurance to men considering vasectomy,” Eric J. Jacobs, PhD, cancer epidemiologist at the American Cancer Society, said in a press release. “Men concerned about developing a fatal prostate cancer should focus on maintaining a healthy weight and, if they smoke, quitting smoking. Both obesity and smoking having consistently been linked with high risk for fatal prostate cancer, as well as with risk for many other diseases.”

Jacobs and colleagues evaluated data from 363,726 men in the Cancer Prevention Study II (CPS-II) cohort, 7,451 of whom died of prostate cancer during follow-up from 1982 to 2012. The analysis also included data from 66,542 men from the CPS-II Nutrition Cohort — a subgroup of the other cohort — of whom 9,133 were diagnosed with prostate cancer during follow-up from 1992 to 2011.

Overall, 42,015 men in the CPS-II cohort and 10,589 men in the CPS-II Nutrition cohort underwent vasectomy. In both cohorts, men with vasectomies were more likely to have more education and were less likely to be obese or current smokers.

Vasectomy did not increase risk for prostate cancer mortality in the CPS-II cohort (HR = 1.01; 95% CI, 0.93-1.1). This association persisted among men who underwent vasectomy less than 35 years ago (multivariable-adjusted HR = 1.01; 95% CI, 0.89-1.14) and 35 years or more ago (multivariable-adjusted HR = 1.02; 95% CI, 0.92-1.14).

In the CPS-II Nutrition cohort, vasectomy did not increase risk for overall prostate cancer incidence (HR = 1.02; 95% CI, 0.96-1.08) or high-grade — defined by a Gleason score of 8 or higher — prostate cancer (HR = 0.91; 95% CI, 0.78-1.07).

This association again persisted regardless of length of time passed since vasectomy.

However, the association between prostate cancer incidence differed by follow-up time (P = .02). There appeared to be a greater risk for prostate cancer incidence from 2007 to 2011, the last 5 years of follow-up (HR = 1.18; 95% CI, 1.03-1.35), which was driven by the risk for nonaggressive prostate cancer (HR = 1.3; 95% CI, 1.11-1.53) and not aggressive disease (HR = 0.88; 95% CI, 0.65-1.18).

Vasectomy was associated with a lower risk for prostate cancer mortality in the CPS-II Nutrition cohort (HR = 0.79; 95% CI, 0.64-0.98), which the researchers noted was an unexpected finding.

The researchers acknowledged that the fact that the participants’ wives reported their vasectomy status may be a limitation to these findings. Further, data on vasectomies after study enrollment may have been misclassified.

“Because this study, like all observational studies, has some potential for bias, a small increase in risk cannot be entirely ruled out,” Jacobs and colleagues wrote. “However, our results provide some reassurance that vasectomy is unlikely to meaningfully increase risk for prostate cancer.” – by Alexandra Todak

Disclosure: The researchers report no relevant financial disclosures.