Impact of Screening on Breast Cancer Mortality Assessed in Danish Study
Posted: Tuesday, October 16, 2018
Using different models to assess the effects of screening on breast cancer mortality, Professor Elsebeth Lynge, of the Department of Public Health, University of Copenhagen, Denmark, and colleagues found a 20% reduction among women diagnosed during the recommended screening age range. However, they noted, this effect was “restricted to breast cancer deaths in women who could potentially benefit from screening.” Their study findings were published in the Journal of Clinical Oncology.
“Our study highlights the complexity in evaluating the long-term effect of breast cancer screening from observational data,” the authors stated. “Screening is clearly beneficial but, after screening age, only for a diminishing proportion of women.”
The study centered on 18,781,292 person-years of data from Copenhagen and Danish registries; of them, 976,743 person-years were from women invited to screening and 17.804,549 person-years were from control subjects. Those invited to screening every 2 years were women between the ages of 50 and 69 years.
The authors used three models to examine the data: a “naïve model,” which included all breast cancer deaths; a “follow-up model,” which included only breast cancer deaths in women diagnosed after their first invitation to screening; and an “evaluation model,” which included only breast cancer deaths and person-years in women diagnosed during screening age. In the naive model, the breast cancer mortality rate was lower with screening than without, with an age-adjusted rate ratio of 0.90 (10% risk reduction). In the follow-up model, the same was true, with an age-adjusted rate ratio of 0.89 (11% risk reduction). In the evaluation model, again, the breast cancer mortality rate was lower with than without screening, with an age-adjusted rate ratio of 0.80 (20% risk reduction).
