Researchers in Denmark have revealed that breast cancer screening is not associated with a decreased number of incidences of advanced breast cancer. This study is published in the Annals of Internal Medicine journal.
Breast cancer screening by 40 years of age or earlier in the presence of a family history or a risk factor is now generally accepted and is a standard of care.
Although a screening mammography detects many clinically important tumors at an earlier stage, it also identifies many small and clinically insignificant tumors as well. This overdiagnosis eventually leads to unnecessary surgeries, chemotherapy, and radiotherapies which impose patients to other certain risks.
A new study, which is published in the Annals of Internal Medicine journal, has examined the association of breast cancer screening with a reduction in advanced breast cancer incidence (occurrence of new cases in a time period) and has estimated the level of overdiagnosis in Denmark.
In this cohort study, all Danish women in the range of 35 to 85 years old diagnosed with advanced breast cancer were evaluated from 1980 to 2010 from two databases in Denmark. This study compared the rate of overdiagnosis in screened and non-screened patients.
Advanced breast cancer was defined as tumors larger than 20 mm in diameter and all tumors sized 20 mm or less than 20 mm in diameter were considered non-advanced. Trends in incidence of advanced and non-advanced breast cancer were compared in screened and non-screened women.
Based on the results, breast cancer screening was not associated with a decreased incidence of advanced breast cancer, while the incidence of non-advanced breast cancers had increased with screening.
Authors have concluded that breast cancer screening in Denmark, which is now performed for 17 years, was associated with a significant number of increased cases of non-advanced tumors and Ductal Carcinoma in Situ (or DCIS, a form of non-invasive breast cancer characterized by proliferation of malignant ductal epithelial cells completely contained within breast ducts). This screening was not associated with a reduction in the incidence of advanced breast tumors.
The findings also support the idea that breast cancer screening may not always accomplish the promise of reduction in invasive therapy or disease-specific mortality.
Written By: Nima Makhdami, M.D.