Even if there is a weak association between vasectomy and subsequent prostate cancer, we believe that large-scale studies on this question should be of low priority in developing countries where vasectomy is widely practised and where the incidence of prostate cancer is low. Arguments to justify this point of view are presented.
PIP: Studies in the US which have claimed that vasectomy increases the risk for prostate cancer have been evaluated and only weak associations (which may be due to methodological shortcomings) have been found. To resolve this issue, some investigators have called for confirmatory studies in developing countries and have, by this action, increased anxiety, especially in India. 2 examples will show that confirmatory studies are not needed in developing countries because of the low incidence of prostate cancer. The first example uses the total annual incidence of prostate cancer in Bombay (8.2/100,000) and assumes a vasectomy prevalence rate of 5% and a 60% higher risk of prostate cancer for vasectomized men. The implication of this would be that prostate cancer would occur in 8/100,000 nonvasectomized vs. 12.7/100,000 vasectomized men for a population attributable risk of 0.24/100,000/year, and the fraction of the disease attributable to exposure to vasectomy (population attributable fraction) would be 3% of all cases of prostate cancer in Bombay. The second example assumes a relative risk of 3 in a population where 10% of the men are vasectomized. The population attributable risk would be 1.67/100,000/year, and the population attributable fraction would be 0.17. Thus, the potential impact of vasectomy on public health in a country where prostate cancer is uncommon is small, even if a large percentage of the men had vasectomies. Also, the numbers of men to be followed to detect one case of cancer annually in each group would be too large for any realistic prospective study, and it is unlikely that a case-control study would add to our existing information. Thus, longterm studies into the longterm safety of vasectomies should occupy a low priority in developing countries where vasectomy is widely used and the incidence of prostate cancer is low.