ABSTRACT
With passage of time, concerns have arisen about the effi - cacy of breast screening with the Danish Cochrane Centre having published a highly critical review which suggests breast screening saves few lives in relation to the heavy costs of screening (9). In response to the fi rst of these Cochrane reviews, the International Agency for Research on Cancer examined the evidence and concluded that for women aged 50-69, “there is suffi cient evidence from randomized trials that inviting women 50-69 years of age to screening with mammography reduces their mortality from breast cancer.” There is inadequate evidence on the value of screening beyond age 69, but there is some belief that it may benefi t women who are otherwise well and have a life expectancy of 10 years or more (10). A major trial is now underway in the United Kingdom evaluating screening in older women. As for the harms of screening, longer term follow-up of the Two-County study concluded that between 400 and 500 women needed to be screened for seven years to save one life which is consistent with reviews by the United States Preventive Services Task Force (which worked on the basis of number needed to invite) and in Canada (11,12). Overdiagnosis is a major cause of debate, but can only be estimated statistically and never proven. Most estimates are about 10% (13-15) although they can reach up to 30% (9). Another potential accusation made against screening is that it increases the mastectomy rate (16). However, data from England show a mastectomy rate in screened women of around half that of women who present
outside screening (17) and in the Netherlands a case-control study demonstrating a 49% reduction in mortality showed comparable mastectomy rates (18).
