Doctors tend to visualize many diseases as a little army that starts small, enlisting, at most, a soldier or two. If they can locate and flush out the enemy when it's only two or three strong, they figure they can get in there early with their nucle

Because cancers can grow before you get ill or exhibit symptoms, they have been the main target of catch-it-early warfare. For all of us who dread the frightening randomness of "silent" killers like cancer, which have reached epidemic proportions, this is a highly comforting notion. You and I can escape death. We don't need to look after ourselves. All we need to do is have a simple annual screening test.

All this activity may comfort those who wish to see medicine doing something about cancer. But the point is, despite all the money being poured into massive screening campaigns, all the billboards and TV ads, no screening programme anywhere is making the slightest impact on cancer mortality. In fact, because of their inordinately high potential for false positive readings, screening may only be increasing the number of patients mutilated through unnecessary drug treatment or surgery.

In the last three months, the medical literature has been awash with studies on both sides of the Atlantic demonstrating that a number of screening campaigns have no value. The latest study from the University of British Columbia in Vancouver even recommends junking mammograms altogether (see p5). They studied all the trials since the early ones, claiming a 30 per cent reduction in deaths from breast cancer over 50 who've been screened. This 30-per-cent risk reduction has been adopted as a mantra by the medical profession. It has provided a justification of sorts to screen many groups such as women under 50 where benefit has never been shown.

As a perfect example of just how ingrained knee-jerk screening is, Minerva, the pen name of a columnist in the British Medical Journal, cheerily admitted that there is "little hard evidence" but plenty of "sound reasons" for believing that screening for those over 65 is useful. As age is the most important risk factor for the disease, and 65 year olds may go on to live another 12 years, she figured, it's got to be good for them. (BMJ, May 8, 1993).

There has been far less publicity, the Canadian researchers remind us, of all the studies that have been done since those early days, showing that mammography does no good for anyone in any age group, but does great harm through false positives and get-in-there-early intervention. "Since the benefit achieved is marginal, the harm caused is substantial and the costs incurred are enormous, we suggest that public funding for breast cancer screening in any age group is not justifiable," the epidemiologists concluded. It's hard to get any more damning than that. Or than the recent study in Bristol of a quarter million women, showing that cervical screening is a dangerous waste of time.

Nevertheless, it's doubtful that your rank and file doctor will take any of this to heart. If he did, he'd be forced to open up his medicine cabinet and show you his dirty little secret: the cupboard is bare.

!ALynne McTaggart