Introduction: Service mammography has been offered biennially to women aged 50-69 years in the municipality of Copenhagen since 1991. The results were compared to breast cancer cases before initiation of screening. The comparison concerns prognostic factors and the treatment-related consequences.
Material and methods: Data from the Copenhagen service mammography screening were linked to data from the DBCG database.
Results: Before screening, 16% of breast cancer cases had a tumour size of 10 mm or less, this percentage increased to 41 in the screen-detected cases. Sixty per cent of breast cancer cases showed no evidence of metastatic spread to axillary lymph nodes before screening; this percentage increased to 78 per cent in the screen-detected cases. Forty per cent of ductal carcinomas showed a malignancy grade I before screening, compared to 53% in the screen-detected cases. Thirteen per cent were treated with breast conserving therapy before screening, as opposed to 48% in the screen-detected cases. Forty-one per cent needed postoperative adjuvant treatment before screening, compared with 21% in the screen-detected cases.
Discussion: A marked improvement was seen in the prognostic and treatment-related characteristics of the screen-detected breast cancer cases, as compared to breast cancer cases from the same area before screening was initiated.