Comparing the performance of mammography screening in the USA and the UK

Abstract

To compare the performance of screening mammography in the USA and the UK, a consecutive sample of screening mammograms was obtained in women aged 50 and older from 1996 to 1999 who participated in the Breast Cancer Surveillance Consortium in the USA ( n=978,591) and the National Health Service Breast Cancer Screening Program in the UK ( n=3.94 million), including 6943 diagnosed with breast cancer within 12 months of screening. Recall rates were defined as the percentage of screening mammograms with a recommendation for further evaluation including diagnostic mammography, ultrasound, clinical examination or biopsy, and cancer detection rates including invasive cancer and ductal carcinoma in situ diagnosed within 12 months of a screening mammogram. All results were stratified by whether examinations were first or subsequent and adjusted to a standard age distribution. Among women who underwent a first screening mammogram, 13.3% of women in the USA versus 7.2% of women in the UK were recalled for further evaluation (relative risk for recall 1.9; 95% CI 1.8–1.9). For subsequent examinations recall rates were approximately 50% lower, but remained twice as high in the USA as in the UK. A similar percentage of women underwent biopsy in each setting, but rates of percutaneous biopsy were lower and rates of open surgical biopsy were higher in the USA. Women undergo screening approximately every 18 months in the USA and every 36 months in the UK. Based on a 20-year period of screening, the estimated percentage of women who would be recalled for additional testing was nearly threefold higher in the USA. The number of cancers detected was also higher in the USA (55 versus 43), and most of the increase was in the detection of small invasive and in situ cancers. The numbers of large cancers detected (>2 cm) were very similar between the two countries. Recall rates are approximately two to three times higher in the USA than in the UK. Importantly, despite less frequent screening in the USA, there are no substantial differences in the rates of detection of large cancers. Efforts to improve mammographic screening in the USA should target lowering the recall rate without reducing the cancer detection rate.