Thirty five years of randomised trials of mammography have failed to confirm the efficacy of mammograms as a screening tool.

In a review of the history of mammograms, Jane Wells, of the Health Services Research Unit in Oxford, discovered that political and financial pressures, rather than evidence and efficacy, played an often disproportionate part in recommendations in the US and elsewhere that increasingly younger women should be referred for regular screening.

According to Wells, breast cancer is an emotive issue for women, and politicians keen to solicit the female vote were quick to jump on the mammography band wagon. Funding for some research organisations throughout the years appeared to depend on their willingness to recommend universal screening programmes.

Nevertheless, this flies in the face of the medical evidence that for women in their forties, screening does not significantly raise the detection rate or lower the mortality rate from breast cancer. Indeed, it may actually increase the potential for harm since screening in younger women produces a greater number of false positive results. Even for women over 50, for whom screening has been shown to make a difference in mortality, the actual number of deaths involved is comparatively small.

Some commentators, including the Centre for Medical Consumers and the National Breast Cancer Coalition, believe that the controversy over mammograms has diverted attention away from the more pressing problem: our ignorance about how to prevent breast cancer (BMJ, 1998; 317: 1224-9).