A comparison of cancer detection rates achieved by breast cancer screeningprogrammes by number of readers, for one and two view mammography: resultsfrom the UK National Health Service breast screening programme

Objective-To determine the increased cancer detection rate, if any, of prog rammes in the UK National Health Service breast screening programme (NHSBSP ) using more than single reading of mammograms. Design-Information on the detection of cancers by individual screening prog rammes from annual (KC62) returns, supplemented by questionnaire informatio n about the number of readers. Setting-The 87 NHSBSP programmes from England and Wales for the screening y ear 1 April 1996 to 31 March 1997. The study includes all programmes for pr evalent screens where two views are mandatory, but excludes the four progra mmes using two view mammography for incident screening. Main outcome measures-Cancer detection, invasive cancer detection, and smal l (<15 mm) invasive cancer detection by mammographic reading protocol using single reading as the reference level. Results-Programmes collectively using single reading detected the lowest ra te of cancers at both prevalent (first) and incident (subsequent) screening . The highest rate of age standardised cancer detection was achieved by pro grammes using double reading with arbitration. At prevalent screens, where all programmes used two views, those programmes using double reading with a rbitration detected 32% (95% confidence interval (CI) 3% to 69%) more small (<15 mm) invasive cancers than programmes using single reading. At inciden t screens, where all programmes analysed used one view this increased to 73 % (95% CI 40% to 113%). Recall rates showed no obvious difference between s ingle reading and the double reading protocols, being around 7% for prevale nt screens and 3.5% for incident screens. Discussion-The results suggest that the increase in cancer detection result ing from increasing the number of readers depends on the number of views, a nd is higher for one view than two views. Single reading of one view result s in a low detection rate of small invasive cancers for most individual pro grammes. It is, however, recognised that a small number of individual reade rs may achieve high detection rates with such a protocol. All groups of pro grammes using different reader/view protocols are on average close to or ab ove target cancer detection rates, except those using single reading of one view (mediolateral oblique) at incident screens.