Science Articles

A Stitch in Time...

Wed, 4th Aug 2004

Bob Bury

It's not often that medical researchers receive floods of emails accusing them of wholesale murder, and expressing the devout wish that they should die painfully of cancer (unless they use animals in their research, of course).But it happened recently in the States. The hysteria was provoked by the apparently innocuous issue of health screening. Screening is the use of diagnostic tests to discover disease before the patient experiences any symptoms, in the expectation that early treatment is more likely to result in cure, and UK readers will be familiar with the national cervical and breast cancer screening programmes which have been going for some years now.

There is a general assumption that screening is a 'good thing', and that if it is possible to screen for a disease, then we should screen for it. But it's not that simple. Take prostate cancer. There is a blood test to detect a chemical (prostate specific antigen - PSA) which is released into the bloodstream by prostatic cancer cells. It is therefore theoretically possible to offer a blood test to the at-risk population (men over 50, say) to check their PSA level. However, not all men with a raised PSA will have cancer, so an abnormal result triggers a further series of tests. The patient will have an ultrasound examination of the prostate gland, using a probe introduced into the rectum, with up to ten or more needle biopsies (removal of cells for microscopic examination) of any suspicious areas. If cancer is confirmed, the treatment is likely to involve radical surgical removal of the gland, an operation that carries a significant risk of complications, including impotence and incontinence. 'So what?' you say - 'it's better than dying of cancer'. Well yes, but the trouble is, we don't know how many of these men would have died of their cancer. If you look at the prostate glands of men dying in their seventies and beyond of other diseases, up to 40% will contain cancer cells. In other words, more men die with prostate cancer than die of it. The introduction of an expensive screening programme may result in the even more expensive investigation and surgical treatment of many men who would never have been troubled by their slow-growing prostatic cancer had it been left alone. A small but significant proportion of them will suffer the harmful effects of surgery. So suddenly, screening for prostate cancer looks less attractive, and the jury is still out on whether a national screening programme would be worthwhile.

Which is where our unfortunate American medical scientists come in. The Editor and Deputy Editor of the Western Journal of Medicine raised these issues in the San Francisco Chronicle, presenting the arguments against prostate screening. Immediately, a host of special interest groups produced advertisments in the national press villifying the researchers, and calling on their university employers to sack them. The language used was vehement, accusing the hapless scientists of 'geriatricide' - condemning hordes of innocent men to a painful and unnecessary death. Of course, the reaction might have been partly due to the fact that, in the US privatised healthcare system, screening is big business. It's becoming big business in the UK too, with people prepared to pay good money to private healthcare providers for 'health checks', despite the absence of any proof of real benefit.

There is even doubt about the established screening programmes. Some workers question the robustness of the evidence of reduced breast cancer deaths in the screened population, and there is a continuing debate as to whether the huge amounts of money consumed by the screening programme could be better spent elsewhere. Of course, try telling that to the husband and children of one of the many women whose life has been saved by the early detection of a breast cancer. But in a cash-limited healthcare system (and state-funded or private, they are all cash-limited), some hard decisions have to be taken.

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