What should be done about interval breast cancers?

The paper by Woodman and colleagues in this week's journal contains the first published data from the NHS breast screening programme on cancers diagnosed in the three years after a negative screen (“interval cancers”) (p 224).1 It reports 15.8 interval cancers per 10000 women screened in the North West region in the 24 months after screening, which is higher than the target that was set for Britain. Preliminary data from 46 screening centres, collected by the National Breast Screening Radiology Quality Assurance Committee, are very similar, suggesting that the North West region is representative of the United Kingdom as a whole. Comparing rates of interval cancer with those reported in the literature is difficult because different groups have reported the data using different methods and the populations studied have different age compositions. The rates reported today, however, are higher than the rate of 9.4/10000 in the Swedish two county trial2 and are very similar to the rates reported from the Nijmegen (15.7/10000)3 and Stockholm (19.2/10000) trials.4 In Nijmegen in the eight successive screening rounds …