Vasectomy and risk for prostate cancer (all over again)

As long-term readers will be aware, this is a topic that comes up over and over again … about every couple of years … and each time it comes up the question of whether vasectomy really does or really doesn’t increase risk for prostate cancer (by a small amount) gets less and less clear.

So let’s begin with the new data.

A study just published in the Journal of Clinical Oncology (by Jacobs et al.) is based on data from men enrolled in large, epidemiological study known as the Cancer Prevention Study II (CPS-II). There are very limited data about risk for prostate cancer after vasectomy from meaningful, prospective trials (but see below).

Jacobs et al.  looked at two sets of data:

  • The association between vasectomy and prostate cancer-specific mortality among all 363,726 men in the CPS-II.
  • The association between vasectomy and prostate cancer incidence among 66,542 men in the CPS-II Nutrition Cohort (a subgroup of the full CPS-II cohort)

Here is what they found:

  • In the full CPS-II study
    • About 42,000 men had a vasectomy.
    • About 321,000 men did not have a vasectomy.
  • 7,451/363,726 men (2.0 percent) died of prostate cancer in the full CPS-II cohort between 1982 and 2012.
  • 9,133/66,542 men (13.7 percent) were diagnosed with prostate cancer in the CPS-II Nutrition Cohort during follow-up from 1992 to 2011.
  • After controlling for patient age and smoking history
    • Vasectomy was not associated with prostate cancer-specific mortality (hazard ratio [HR] = 1.10) in the entire CPS-II cohort.
    • Vasectomy was not associated with overall incidence of prostate cancer (HR = 1.02) in the CPS-II Nutrition Cohort.
    • Vasectomy was not associated with the incidence of high-grade prostate cancer (HR = 0.91) in the CPS-II Nutrition Cohort when high-grade was characterized simply as a patient having a Gleason score of ≥ 8.

The authors conclude that:

Results from these large prospective cohorts do not support associations of vasectomy with either prostate cancer incidence or prostate cancer mortality.

A study published back in 2014 from the epidemiology research group at Harvard, and based on data from the Health Professionals Follow-Up Study, had reported that vasectomy was associated with an absolute increase in risk for diagnosis with a lethal form of prostate cancer of 3 in 1,000 or 0.3 percent — as opposed to a relative increase of roughly 10 percent in risk for prostate cancer diagnosis and of roughly 20 percent in risk for prostate cancer-specific mortality. (For our original report on  that study, click here.)

Dr. Eric Jacobs, the lead author for the new study from the American Cancer Society was quoted as follows in an article on the HealthDay web site:

It’s not clear why the two studies found somewhat different results. … It should be noted that the increase in risk of prostate cancer observed in the Health Professionals Follow-Up Study was relatively small, so the results of the two studies are not all that different. Sometimes study results differ by chance.

As we have said consistently for many, many years, the increase in risk to a man of dying of prostate cancer after a vasectomy — if there is one — is well understood to be tiny by comparison to the risks associated with pregnancy for a woman as she gets older (and for the consequent child because of the increase in risks for birth disorders). Couples need to keep these two very different sets of risk in mind when they are considering the question of whether or not a vasectomy is appropriate.

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