Abstract
OBJECTIVE: This study analyzes the efficacy of the Icelandic population-based service mammography screening. MATERIAL AND METHODS: Women aged 40-69 were invited for screening at 2-year intervals starting in November 1987. The study evaluates: (A) attendance and other screened performance parameters during 1998-2010; (B) trends in age-standardized and age-specific incidence rates during 1969-2010 and mortality rates during 1969-2010; and (C) distribution of risk factors and disease specific death rates according to mode of detection. RESULTS: (A) In the age group of 40-69, the average 2-year attendance was 62%, recall rate was 4.1%, needle biopsy rate was 1.3%, surgery rate was 0.6%, invasive cancer rate was 0.4%, and ductal carcinoma in situ (DCIS) rate was 0.06%. (B) The linear incidence trend after the start of screening decreased significantly in the age group 40-49, increased significantly in the age group 50-69, but decreased non-significantly in the age group 70-79. The decreased age-specific incidence in the 70-79 age group was, however, greater than the increased age-specific incidence at the ages 50-69. The mortality rate decreased 41% for all age groups and the linear mortality trend decreased significantly at ages 40-49, 50-69, and 70-79. In the age group 40-74 years, the age-specific mortality decreased by 6.9 cases per 2000 during a 10-year period. (C) Screen-detected women had significantly smaller tumors, more favorable tumor grade, fewer axillary metastases and, after correction for other risk factors, the likelihood of dying from cancer decreased 54% (hazard ratio: 0.46; 95% confidence interval: 0.31-0.69) for these patients compared to cases of nonparticipators. CONCLUSION: The study results confirm acceptable rates of recalls and referrals for further diagnosis and treatment, and significantly decreased breast cancer mortality rate after starting screening.