First epidemiological analysis of breast cancer incidence and tumor characteristics after implementation of population-based digital mammography screening.

PURPOSE: To epidemiologically evaluate the impact of digital mammography screening on incidence rates and tumor characteristics for breast cancer.
MATERIALS AND METHODS: The first German digital screening units in the clinical routine were evaluated during the implementation period by using data from the cancer registry to compare the incidence rate of breast cancers and prognostic characteristics. 74 % of women aged 50 - 69 within the region of Muenster/Coesfeld/Warendorf were invited between 10 / 2005 and 12 / 2007 for initial screening; 55 % participated (n = 35 961).
RESULTS: In 2002 - 2004 the average breast cancer incidence rate (per 100,000) was 297.9. During the implementation of screening, the rate rose to 532.9 in 2007. Of the 349 cancers detected with screening, 76 % (265 / 349) were invasive compared to 90 % (546 / 608) of cases not detected with screening during the same period. 37 % (97 / 265) of cancers detected in the screening program had a diameter of <or= 10 mm and 75 % (198 / 265) were node-negative compared to 15 % (79 / 546) and 64 % (322 / 503), respectively, in cancers detected outside the screening program. The distribution of invasive tumor size (pT categories) and the nodal status differed with statistical significance between cancers detected in and outside the program (p = 0.005 and p = 0.004, respectively).
CONCLUSION: Epidemiological data shows that the implementation of a population-based screening program led to a relevant increase in the age-specific breast cancer incidence rate. The characteristics of breast cancers detected in the screening program comply with the requirements of the European guidelines and are significantly favorable compared to tumors diagnosed outside the program. These findings indicate that digital mammography screening fulfills the requirements for an early tumor detection tool.