VASECTOMY DOES NOT INCREASE PROSTATE CANCER RISK

New observational data from a large US cohort does not support an association between vasectomy and either prostate cancer incidence or mortality.

"There have been few previous large studies of vasectomy and prostate cancer. This study is the largest study of vasectomy and fatal prostate cancer to date and provides evidence that having a vasectomy is unlikely to meaningfully increase risk of developing or dying from prostate cancer," lead author Eric J. Jacobs, PhD, strategic director, pharmacoepidemiology, American Cancer Society, Atlanta, Georgia, told Medscape Medical News.

The study was published online September 19 in the Journal of Clinical Oncology.

This study is "reassuring because it reports prostate cancer mortality as opposed to only describing risk of being diagnosed with prostate cancer," commented Behfar Ehdaie, MD, MPH, surgeon and prostate cancer expert from Memorial Sloan Kettering Cancer Center in New York City. He wasn't involved in the study and was approached for comment by Medscape Medical News.

"Importantly, the data for detection of low- vs high-risk prostate cancer and prostate cancer mortality are consistent and suggest no association with prostate cancer mortality and vasectomy," Dr Ehdaie commented.

"The data reported in this study and combined with prior studies leads us to be more confident that discussing risk of prostate cancer mortality in men who consider vasectomy is not obligatory," he added.

Larger Study, Different Result

As reported previously by Medscape Medical News, data published in 2014 from the Health Professionals Follow-Up Study found a modest 10% higher risk for overall prostate cancer and about a 20% higher risk for high-grade (Gleason score 8 to 10) and lethal prostate cancer with vasectomy. That study was based on a prospective cohort of 49,405 men, of whom 12,321 (25%) had undergone vasectomy; after 24 years of follow-up, 6023 patients had been diagnosed with prostate cancer.

However, this latest and much bigger study found no association between vasectomy and prostate cancer mortality. This latest study analyzed data for 363,726 men in the Cancer Prevention Study II (CPS-II) cohort, of whom 42,015 (11.5%) were determined to have undergone vasectomy. During follow-up (1982 to 2012), 7451 men died of prostate cancer.

Dr Jacobs and colleagues note that the previous study included just over 800 prostate cancer deaths, while this latest study included more than 7000, and that differing results could have been a result of chance. 

"While a previous study suggested an association, our results show no connection between vasectomies and overall risk of prostate cancer, or of dying from prostate cancer, and should provide some reassurance to men considering vasectomy," he said in a statement.

Dr Jacobs and colleagues report that vasectomy was not associated with prostate cancer mortality (hazard ratio [HR], 1.01; 95% confidence interval [CI], 0.93 - 1.10). The results were similar by years since vasectomy (<35 -="" 0.89="" 0.92="" 1.01="" 1.02="" 1.14="" age="" and="" attained="" between="" ci="" education="" follow-up="" hr="" interactions="" multivariable-adjusted="" no="" or="" p="" significant="" since="" there="" time="" vasectomy:="" vasectomy="" were="" years="">

The results were also similar in analyses restricted to men age 50 years or older when vasectomy status was ascertained in 1982 and therefore less likely to have sought vasectomy during follow-up (HR, 1.03; 95% CI, 0.94 - 1.12), the researchers note.

They also examined the association between vasectomy and prostate cancer incidence in 66,542 men in the CPS-II Nutrition Cohort, a subgroup of the CPS-II cohort. During follow-up (1992 to 2011), 9133 were diagnosed with prostate cancer.

Vasectomy was not associated with overall prostate cancer incidence (HR, 1.02; 95% CI, 0.96 - 1.08) or high-grade prostate cancer incidence (HR, 0.91; 95% CI, 0.78 - 1.07 for cancers with Gleason score 8 or higher). Again, results were similar when examined by years since vasectomy and when restricted to men age 50 years or older when vasectomy status was ascertained in 1982.

The researchers did find a slight increase in risk for nonaggressive prostate cancer during the last 5 years of the study period (HR, 1.30; 95% CI, 1.11 - 1.53), although this could be a chance finding, the researchers say.

Clinical Implications

"It is important to clarify whether vasectomy is associated with risk of prostate cancer, particularly with risk of more serious and fatal prostate cancers, to make well-informed choices about long-term methods of birth control," Dr Jacobs and colleagues write. "Clinical guidelines from the American Urological Association state that vasectomy is not a risk factor for prostate cancer, and therefore, clinicians need not discuss risk of prostate cancer in prevasectomy counseling."

The new data "provide some reassurance that vasectomy is unlikely to meaningfully increase risk of prostate cancer," the researchers conclude.

"This study," Dr Ehdaie told Medscape Medical News "confirms what we have observed in other studies: that prostate cancer mortality is not associated with vasectomy status. Specifically, it is difficult to disentangle the bias of being closely monitored by a urologist in men who have undergone vasectomies and risk of being diagnosed with prostate cancer. However, this study is noteworthy to report prostate cancer mortality rates."

He added, "Patients who undergo vasectomy do not need to be monitored any differently for prostate cancer or treated more aggressively compared to men who have never undergone a vasectomy." With this study, "doctors can better counsel patients regarding the short-term and long-term risks of vasectomy."

Dr Jacobs told Medscape Medical News, "Doctors and their patients concerned about developing the worst kind of prostate cancer, fatal prostate cancer, should focus on maintaining a healthy weight and, if they smoke, focus on quitting smoking. Both obesity and smoking have consistently been linked with higher risk of fatal prostate cancer, as well as with risk of many other diseases."

The study was supported by the American Cancer Society, which funded the creation and maintenance of the CPS-II cohort. The authors have disclosed no relevant financial relationships.

J Clin Oncol. Published online September 19, 2016. Abstract

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