Performance of screening mammography in organized programs in Canada in 1996

Background: The results of randomized trials show that breast cancer screen ing by mammography reduces breast cancer mortality by up to 40% in women ag ed 50-69 years. Because of these results, by 1998, 22 countries, including Canada, had established population-based organized screening programs. This paper presents the results of screening mammography in 1996 for 7 provinci ally organized breast cancer screening programs in Canada. Methods: Analyses of interim performance indicators for screening mammograp hy have been calculated from data submitted to the Canadian Breast Cancer S creening database. The data set consisted of data from 7 provincial program s and was limited to mammographic screens for women aged 50-69 years (n = 2 03 303). Screening outcomes and performance indicators were calculated for abnormalities detected by screening mammography only. Results: The abnormal recall rate was 9.5% for first screens and 4.6% for s ubsequent screens, and the cancer detection rate per 1000 women screened wa s 6.9 for first screens and 3.8 for subsequent screens. The positive predic tive value (i.e., the proportion of women who tested positive by mammograph y who were found to have breast cancer on screen-initiated diagnostic work- up) increased from 7.2% at the first screen to 8.2% at subsequent screens. Estimated participation rates within organized programs varied from 10.6% t o 54.2%, depending on the province. Interpretation: For 1996, organized breast cancer screening programs met or exceeded many of the interim measures used in international programs. It i s possible to translate the benefits of breast cancer screening by mammogra phy, as demonstrated in randomized trials, into population-based community programs. Screening mammography through organized programs should increase to allow more comprehensive monitoring in Canada.