Vasectomy has been reported to be associated with an increased risk of prostate cancer in western countries. A hospital-based case-control study was conducted in 12 cities in China to evaluate the relationship between vasectomy and prostate cancer risk in China, a low-risk country with rising incidence and increasing use of vasectomy. Interviews were conducted with 138 histologically confirmed prostate cancer cases diagnosed during 1989-1992 and 638 controls (158 hospital cancer, 158 hospital noncancer, and 322 neighborhood controls) of similar ages. Vasectomy at least 10 years prior to interview was reported by 10% of the cases versus 3% of the controls. Odds ratios for prostate cancer associated with vasectomy were 2.0 (95% confidence interval, 0.7-6.1), 3.3 (95% confidence interval, 1.0-11.3), and 6.7 (95% confidence interval, 2.1-21.6), respectively, when hospital cancer, hospital noncancer, and neighborhood controls were used for comparison. Although detection bias is of concern, the data suggest that in China, men with a history of vasectomy may experience an increased risk of prostate cancer.
PIP: This paper reports the findings of a hospital-based case-control study that was conducted at major teaching hospitals in 12 cities in China. China reports the lowest incidence in prostate cancer of over 100 registries reporting cancer incidence. This investigation evaluated the relationship between vasectomy and prostate cancer and attempted to identify any etiological factor. A total of 138 study patients (index cases) were identified. Controls used in this study included a cancer control and a noncancer control from the same hospital, and 2 neighborhood controls. Chances of having prostate cancer were statistically determined by logistic regression analysis with age group adjustments made. The analysis reviewed 138 cases and 638 controls. Results indicate that, regardless of the variable control used for comparison, an increased risk of prostate cancer was associated with having had a vasectomy. Statistical odds ratio was 2.0 for hospital cancer controls (95% confidence interval [CI]; 0.7-6.1); 3.3 for hospital noncancer controls (95% CI; 1.0-11.3); and 6.7 for neighborhood controls (95% CI; 2.1-21.6). The authors conclude that, as reported for men in Western countries, Chinese men who have had a vasectomy are at significantly increased risk for developing prostate cancer compared to men who never have had a vasectomy. They report a near 2-fold increase in risk (vasectomy vs. non-vasectomy) in developing the disease. Conclusions about cause and effect are premature, but these findings warrant further investigation of several issues. These include: changes in the endocrine system due to vasectomy; systematic and local immunity changes after vasectomy; and other possible biochemical factors that enhance/inhibit cancer growth in the prostate gland.