Over-diagnosis in mammographic screening due to competing risk of death
A partir de données d'incidence du cancer du sein et de données des registres des décès en Angleterre et en Norvège, cette étude de modélisation estime le taux de surdiagnostic associé à un programme de dépistage par mammographie
Background: Different definitions and estimates of over-diagnosis in mammographic screening reflect a substantial need to investigate and understand the complexity of the issue. This modelling study aims to estimate the number of over-diagnosed women, defined as those diagnosed with breast cancer who die from any cause within the lead-time period.
Methods: We used numbers from incidence- and death statistics available online and published estimates of lead-time. Postulated cohorts of screened and not screened women aged 50-51 were followed for a period corresponding to ten biennial screening exams during 20 years, and a further ten years, to age 78-79. The increase in breast cancer incidence due to screening was estimated based on lead-time. The proportion of women diagnosed with breast cancer who died within the lead-time period was assessed based on the differences in the cumulative number of breast cancer diagnosed in a non-screened and screened cohort.
Results: The proportion of inevitable over-diagnosed women in a screened versus non-screened cohort was 1.9% for England & Wales and 1.8% for Norway. Sensitivity analyses using various assumptions increased the estimates up to a maximum of 4%.
Conclusions: The proportion of women with breast cancer diagnosed after participation in a screening program who died within the estimated lead-time period was less than 4%. This inevitable proportion of over-diagnosis should be emphasized in the definition and communication of the issue.
Impact: The issue of over-diagnosis is complex and estimates should be interpreted with substantial care.
Cancer Epidemiology Biomarkers & Prevention , résumé, 2016