The cancer establishment was recently rocked to its core when Professor Michael Baum, an eminent and well-respected breast surgeon and researcher, claimed that screening for breast cancer should be scrapped because it caused hundreds of healthy women to undergo risky, mutilating and unnecessary treatments even when they may never develop the disease. His comments, made at a meeting of the Royal Society of Medicine, cut even more deeply because Baum was one of the physicians who helped set up the UK’s £50-million-a-year breast-screening service (Frith M, Scrap Breast Cancer Screening, Evening Standard, 10 December 2002, p 1).

Baum has stated publicly that the most dramatic consequence of the rise in the numbers of routine mammographies has been a huge increase in the incidence of small, well-contained, relatively benign breast cancers known as ductal carcinoma in situ (DCIS) (BMJ Rapid Responses at bmj.com/cgi/eletters/325/ 7361/418#24945, 24 August 2002).

Early in 2002, the American Cancer Society predicted that nearly 48,000 new cases of DCIS would be diagnosed in the US that year - an increase of around 900 per cent - compared with the rate in 1983, when only 4900 cases were diagnosed.

Some would consider this a rise of epidemic proportions while others argue that it’s just mammography picking up anomalies that were there all along but, in the majority of women, never developed into full-blown cancer. Indeed, based on autopsies, it is estimated that at least half of the cases of DCIS would not progress to an invasive cancer if left undetected (Br J Cancer, 1987; 56: 814-9).

There is even, within medical circles, hot debate over whether DCIS is even a cancer at all. These tiny cancers, which are entirely confined within the milk duct tissue, are often described in a diagnosis as a 'precancer' - even though the condition is malignant (and has the potential to become a full-blown invasive cancer). Because doctors don't know which cases of DCIS will become invasive and which will not, all are treated in the same manner - usually with surgery backed up by hormone therapy and irradiation.

The survival rate for DCIS is something in the region of 98 per cent. But the question is whether it is the early and aggressive treatment or the nature of the disease that is responsible for the numbers of women who go on to live normal healthy lives after DCIS. Given the studies showing that mammography makes no difference to outcome (Ann Intern Med, 2002; 137: 305-12; 344-6; 361-2; 363-4), many now believe it is the latter.