ABSTRACT
BACKGROUND: Several case-control and cohort studies since the early 1990s have shown conflicting results on a possible association between vasectomy and prostate cancer risk. A recent systematic review failed to show a causal association and suggested several possible mechanisms for inconclusive results. This study addressed some of these limitations.
POPULATION STUDIED: The study included 923 men in New Zealand between the ages of 40 and 74 years with newly diagnosed prostate cancer (cases). All men were on the general electoral roll and had a history of marriage. The control group was randomly selected from the general electoral roll (n = 1224), and frequency matching to cases was performed in 5-year age groups. The mean age for cases and controls was 66.3 and 65.1 years, respectively. All cases and controls had telephone numbers for data collection purposes. Because nearly all study subjects were of European descent (97%), the results may not apply to other ethnic groups.
STUDY DESIGN AND VALIDITY: This national, population-based, case-control study was performed on all newly diagnosed cases of prostate cancer during a specified time (April 1, 1996, to December 31, 1998). Controls were randomly selected from the general electoral roll in which about 95% of adults are listed. Of potential cases and controls, only 12% and 20%, respectively, could not be contacted due to death, doctor or subject refusal, severe illness, inability to trace, or language difficulties.
OUTCOMES MEASURED: The primary outcome measured was the relative risk (RR) of prostate cancer for men who had vasectomies compared with that for men who had not undergone the procedure.
RESULTS: No association between prostate cancer and vasectomy was found (RR = 0.92; 95% confidence interval [CI], 0.75–1.14). Even after 25 years since vasectomy, no association was found (RR = 0.92; 95% CI, 0.68–1.23). Adjustments were made for social class, geographic region, religious affiliation, and family history of prostate cancer without any effect on the risk.
This study found that having a vasectomy does not increase a man’s risk of developing prostate cancer, even after 25 or more years of follow-up. Because a previous systematic review also showed no conclusive evidence for an increased risk of prostate cancer after vasectomy, practitioners can confidently advise patients requesting vasectomies of the safety advantages compared with other methods of sterilization.