Quality assurance and cancer detection rates in a provincial screening mammography program. Work in progress

In 1990, a provincial screening program was inaugurated in Alberta, a Canadian province of 2.4 million people. The goal of the program is to decrease the number of deaths from breast cancer by 30% in women aged 50-69 years. In the first 18 months of program operations, efforts were concentrated on high levels of quality assurance in all areas of program activities. In particular, the abnormality referral rates, cancer detection rates, and size and stage of mammographically detected cancers were evaluated. Of the 9,553 women seen, 8,524 were between the ages of 50 and 69 years. Reported abnormality rates were initially more than 16%, but were brought down steadily to less than 5%. Cancer detection rates increased with age, ranging from 1.9 cancers detected per 1,000 women aged 40-49 years to 14.1 cancers per 1,000 women aged 70 years and older. Forty-one of the 61 cancers detected (67%) were less than 1.5 cm in diameter. Forty-three of the 52 cancers (83%) in which the nodal status was known were node negative. At the conclusion of the first 18 months of operation, interpretation parameters were within the target zones expected for a population-based screening program.