Position paper: Breast cancer screening, diagnosis, and treatment in Denmark

Background. During the last decades the diagnosis, treatment, and prognosis of breast cancer have changed and improved in Denmark. The first mammography screening programme started in 1991. However, for many years only about 20% of Danish women aged 50-69 were offered screening. The national roll-out of screening took place in 2008-2010. Material and methods. Based on published Danish data, this overview describes the status of diagnosis and treatment, and the screening programme. For further evaluating the potential overdiagnosis and overtreatment, additional Danish Breast Cancer Cooperative Group (DBCG) data are included. Results and conclusion. Using incidence-based mortality method, reduction in breast cancer mortality was estimated to be 25% in the target group of women after 10 years of screening in Copenhagen; an outcome comparable to that of randomised controlled trials. A recent Danish study has indicated overdiagnosis to be around 4%. Others have estimated overdiagnosis to be 33%. National DBCG data showed that the rude breast cancer incidence increased during the period 1990-2011 from 126 to 206 per 100 000. The incidence was almost constant for women younger than 50 years. In regions not offering screening, the incidence increased with 3% per year for women aged 50-69 years with similar trends for small and large tumours. After introduction of screening the increase in the age group 50-69 years was confined to small tumours <= 20 mm, and most pronounced for node negative patients. From the 1990s, the use of breast conserving surgery has increased from around 25% to 69% in 2010. Screening has not increased the number of mastectomies. Breast cancer treatment in Denmark is evidence based and in agreement with international recommendations. After the introduction of mammography screening the absolute number of patients with a more advanced stage at diagnosis and the absolute number of patients undergoing mastectomy have decreased.