The absolute increase in risk of prostate cancer after a vasectomy

Late last week we commented briefly on a paper by Siddiqui et al. that had assessed the association between risk for a diagnosis of prostate cancer and the prior occurrence of a vasectomy in men who participated in the Health Professionals Follow-up Study (HPFS).

In the abstract of their paper, Siddiqui et al. had stated that, based on their data from 49,405 men, of whom 12,321 (24.9 percent) had vasectomies and 6,023 (12.2 percent) went on to be diagnosed with prostate cancer over a follow-up period of 24 years:

  • Vasectomy was associated with a small overall increase in relative risk (RR) for prostate cancer (RR = 1.10).
  • This relative risk level was a little higher among
    • Men diagnosed with a Gleason score  of 8 to 10 (RR = 1.22)
    • Men with “lethal” prostate cancer, i.e., men who actually died of prostate cancer or had distant metastasis (RR = 1.19)
  • Among men receiving regular PSA screening, the association between a vasectomy and relative risk for lethal cancer was stronger (RR = 1.56).
  • There was no association between vasectomy and relative risk for low-grade or localized disease.

However, the abstract provided us with no guidance about absolute risk (i.e., the difference between the risk for lethal prostate cancer among men who had a vasectomy and those who did not).

We have now had the opportunity to review the full text of the paper by Siddiqui et al. and to discuss the paper with the lead author. This has clarified issues for us, as follows:

  • The absolute increase in risk for diagnosis with a lethal prostate cancer among men who had a vasectomy, in this study, was 0.3 percent or 3 in 1,000. This is a statistically significant increase in risk, but it is still pretty small.
  • This increase in absolute risk only becomes evident after the statistical adjustments made to take account of a wide range of relevant factors (including things like race, age, height, weight, smoking history, etc.).
  • The actual percentages of patients who were diagnosed with lethal prostate cancer  in this study were
    • 12 percent among the 1,524 men who had prostate cancer and had had a vasectomy (i.e., about 183/12,321 or 1.5 percent of all the men who had had a vasectomy)
    • 15 percent among the 4,499 men who had prostate cancer and had not had a vasectomy (i.e., about 675/37,084 or 1.8 percent of all the men who had not had a vasectomy)

In other words, whether you have a vasectomy or not, your chance of  a diagnosis of lethal prostate cancer is something like 1.5 to 2 percent. And if you do have a vasectomy (after the adjustments made in this study to allow for the factors above-mentioned) the increase in your risk for diagnosis of a lethal prostate cancer is only of the order of 0.3 percent.

So, based on the data from this study, yes, it does appear that a vasectomy is associated with a small increase in risk for a lethal prostate cancer (but we still have no idea why).

What are the risks associated with not having a vasectomy? There are several, most particularly among wives and partners who are no longer in their prime years for child-bearing:

  • A simple unwanted pregnancy
  • Complications of pregnancy
  • Increased risk for birth of a child who has a condition like Down syndrome or some other disorder associated with pregnancy among older mothers
  • Death as a complication of pregnancy

In other words, even if a vasectomy does increase risk for lethal prostate cancer, that risk may be significantly lower than the risks to a couple and their family associated with a pregnancy later in life. While there are other ways to prevent pregnancy, a vasectomy is widely considered to be one of the most effective method available today — and (assuming no religious objections) the onus should be as much on a man as on his partner to recognize and manage that risk. However, the decision whether to have a vasectomy or not is a very personal one.

Are there other risks associated with having a vasectomy? Yes, there are. They include things like infection, bruising, bleeding into the scrotum and various forms of “post-vasectomy pain syndrome”. A vasectomy is a form of surgery, and all surgeries come with some degree of risk for complications and side effects.

Editorial note: The “New” Prostate Cancer InfoLink thanks Dr. Lorelei Mucci (the senior author) for providing us with the full text of  this paper and Dr. Mohummmad Minhaj Siddiqui (the lead author) for making the time to discuss the statistical details with us over the phone.


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