Vasectomy, a widespread form of birth control, is associated with a small but significantly increased risk of prostate cancer over the long run, according to a comprehensive analysis of Danish nationwide registries. "The precise etiology of prostate cancer is unknown, but cohort studies suggest that reproductive factors influence disease development," comment the authors, led by Anders Husby, MD, Statens Serum Institut, Copenhagen, Denmark. "We showed that vasectomy is associated with a long-term increased risk of prostate cancer, which manifests itself from ten years after the procedure," investigators add. "[However], the absolute increased risk of prostate cancer following vasectomy is...small and similar to the increased breast cancer risk in women following oral contraceptive use," they state. The study was published online May 23 in the Journal of the National Cancer Institute (JNCI). In an accompanying editorial, lead editorialist Lorelei Mucci, MPH, Harvard T.H. Chan School of Public Health in Boston, and colleagues remain unconvinced and conclude that "it remains unclear whether vasectomy is or is not a cause of prostate cancer." In addition, they recommend that "a man's decision to undergo vasectomy should be decided based on the totality of evidence and consideration of benefits and possible risks." Approximately 500,000 men in the United States undergo a vasectomy every year, they note. Details of the Findings The investigators used Danish national health registers to establish a nationwide cohort of 2,150,162 Danish males born between January 1937 and December 1996. The analysis involved some 53.4 million person-years of follow-up, or an average follow-up of 24.8 years per male. At the end of the analysis, vasectomized men had a 15% increased relative risk of prostate cancer compared with nonvasectomized men, the investigators report. The association between time since the procedure was done and the risk of both low and intermediate-to-advanced stage tumors was similar, except for the first year following vasectomy where investigators found a 3.5-fold higher risk of vasectomized men presenting with low-grade prostate cancer compared with men who had not undergone the procedure. "When restricting the analysis to metastatic and extracapsular prostate cancer, we still found a statistically significant increased long-term prostate cancer risk associated with vasectomy," investigators point out. In contrast, men who had undergone a vasectomy had, on average, a lower risk of other cancers compared with nonvasectomized men, suggesting that men who chose to undergo vasectomy are, on average, healthier than the general population. Source
