The controversy about whether breast cancer screening with mammography increases survival or only causes anxiety and healthcare costs for women continues. A recently published Norwegian study on mammography screening and breast cancer mortality looked at all Norwegian women aged 50 to 79 between 1986 and 2005. Norway provides an ideal setting to evaluate the effects of breast cancer screening because of the well-defined population and access to medical records. The study shows that breast cancer screening with mammography reduces deaths from breast cancer by 28%.
During the study period, 49 women out of 100,000 who underwent mammography screening died from breast cancer while 70 women out of 100,000 who did not undergo screening died. The study found that 368 women needed to be screened biannually to prevent one death from breast cancer. The Norwegian study is consistent with other studies from Denmark and Finland that show about a 25% reduction in breast cancer deaths from screening.
Although there has been ongoing controversy about the benefits of mammography, there is no doubt that deaths from breast cancer have significantly decreased as a result of breast cancer screening. On the other hand despite advances in cancer care treatment, the mortality rates based on stage of disease at diagnosis have not changed significantly. Accordingly, the decrease frequency of death from breast cancer is a result of detecting cancers at an earlier stage. Even delays after diagnosis but before treatment affect survival. Mammography's ability to detect asymptomatic cancers at an early stage is responsible for this decline.