English summary: THE ROLE OF SCREENING IN DETECTING BREAST CANCER IN FINLAND

Background: A nationwide mammographic screening of women aged 50 to 59 years commenced in Finland in January 1987. We studied the effect of screening on surgical diagnosis and treatment of breast cancer in one geographic area in Finland.

Methods: We reviewed the medical records of all women (n = 823) who underwent surgery of breast cancer in the Mikkeli Central Hospital between 1987 and 2002. Altogether 35 parameters including preoperative symptoms, diagnostic procedures, operative data, histology and staging were recorded. The clinical data on tumours detected by mammographic screening (n = 120) and invited to screening (n = 134) were compared with tumours detected outside of screening programme (n = 569).

Results: Over 60% of all breast cancers are still detected as a palpable lump, and only one of five cancers were detected as a result of mass screening. Approximately 30 women per 100 000 inhabitants were referred annually from mass screening for surgical biopsies, in 60% of which cancer was detected. Breast cancer was found at an earlier stage by screening.

Conclusion: Cancers detected by mammographic screening are smaller and slower growing than those detected by other means. The mass screening programme may detect only 20% of all breast cancers in Finland.