Use of Two View Mammography Compared with One View in the Detection of Small Invasive Cancers: Further Results from the National Health Service Breast Screening Programme

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Abstract
Objective—: To examine further the effect of using two view mammography in comparison with one view mammography in the detection of small (<15 mm) invasive cancers for programmes in the National Health Service breast screening programme (NHSBSP). The study is in two parts: First the effect on the small invasive cancer detection rate for programmes that changed from using one view to two views for first (prevalent) screens, and secondly the effect on the small invasive cancer detection rate for programmes that used two views for subsequent (incident) screens compared with programmes that used one view. Setting—: Screening programme data from the NHSBSP. Methods—: Data were collated from all screening programmes in the United Kingdom on standard “Korner” returns (KC62 forms) for the screening years 1 April 1994 to 31 March 1995 and 1 April 199S to 31 March 1996. The comparison between one and two view mammography was made using indirectly age standardised invasive cancer detection rates. Results—: For prevalent (first) screens, programmes changing from one view mammography in 1994/95 to two views in 1995/96 reported a 45% (95% confidence interval (CI) 25% to 68%) increase in the detection of invasive cancers of <15 mm. In comparison, programmes that were already using two views in 1994/95 showed no change in 1995/96. For incident (subsequent) screens the small number of programmes that have opted to use two views reported 25% (95% CI 1% to 55%) more invasive cancers of <15 mm than programmes using one view in 1995/96, and 42% (95% CI 11% to 81%) more in 1994/95. Conclusions—: These results confirm the benefit of using two view mammography in the detection of small invasive cancers, and provide evidence that this effect is seen in subsequent screens as well as the first screen.