Vasectomy link to increased risk of prostate cancer

MEN WHO have had a vasectomy are more likely to develop prostate cancer and the risk increases considerably with time, according to two studies of more than 73,000 American men.

The findings show that the overall increased risk is between 56 and 66 per cent. For men who have had their vasectomies for more than 20 years the risk is between 85-89 per cent greater. The risk persisted when factors such as diet, exercise, smoking and drinking and body mass were accounted for.

A causal link has not been established nor is the mechanism by which cancer may be triggered known. But American health experts are advising that men who are considering the operation should be counselled about the possible risks. Those aged between 50 and 70 years who already have a vasectomy should have a yearly rectal examination and blood test. However, they say that the data is 'far too preliminary' to consider a vasectomy reversal to reduce any risk of cancer, and more research is necessary to confirm the findings.

Previous studies have suggested an association between a vasectomy and prostate cancer but the two new studies - published in today's issue of the Journal of the American Medical Association - are the largest to date.

In one study 10,005 men who had had a vasectomy were compared with 37,800 who had not. Most of the men were white and married; the men with a vasectomy were slightly younger than those without - an average of 52 years to 54 years.

A team lead by Edward Giovannucci, of the Brigham and Women's Hospital in Boston, found that between 1986 and 1990 there were 300 new cases of prostate cancer. 'Vasectomy was associated with an overall 66 per cent elevated risk of prostate cancer,' he writes. 'Men who had had their vasectomy for more than two decades (at least 22 years past) had an 85 per cent elevated risk . . . .'

The second study by the same researchers involved 13,034 vasectomised men and 12,306 non- vasectomised men. Between 1976 and 1989, 96 new cases of prostate cancer were diagnosed; overall the risk was 56 per cent and for men who had had their operation 20 years or more before the risk was 89 per cent.

The authors suggest various physiological changes following a vasectomy may be responsible for an increased cancer risk including a reduction in prostatic secretions and possible suppression of tumour immunity. They emphasise that the 'importance of vasectomy as a contraceptive procedure requires that these findings be confirmed by other studies'.

In an accompanying editorial, Dr Stuart Howards, from the University of Virginia Health Sciences Center, and Dr Herbert Peterson, from the Centers for Disease Control and Prevention in Atlanta, say that while both studies are of 'high quality' the causes of prostate cancer remain unknown.

They point out that one in 11 American men will develop the disease and the majority of them will not have had a vasectomy. In addition, the vasectomised men in one study had a lower death rate than the non-vasectomised control group. There were 12,230 cases of prostate cancer in the UK in 1987, the last year for which figures are available.