Effectiveness of and overdiagnosis from mammography screening in the Netherlands : population based study
Menée à partir de données néerlandaises et de données de l'Organisation Mondiale de la Santé, cette étude analyse, pour la période 1989-2012, l'effet d'un programme biennal de dépistage du cancer du sein par mammographie sur l'incidence de cancers mammaires de stade II à IV et la mortalité spécifique, puis estime le taux de surdiagnostic
Objective : To analyse stage specific incidence of breast cancer in the Netherlands where women have been invited to biennial mammography screening since 1989 (ages 50-69) and 1997 (ages 70-75), and to assess changes in breast cancer mortality and quantified overdiagnosis.
Design Population based study : Setting Mammography screening programme, the Netherlands.
Participants Dutch women of all ages, 1989 to 2012.
Main outcome measures : Stage specific age adjusted incidence of breast cancer from 1989 to 2012. The extra numbers of in situ and stage 1 breast tumours associated with screening were estimated by comparing rates in women aged 50-74 with those in age groups not invited to screening. Overdiagnosis was estimated after subtraction of the lead time cancers. Breast cancer mortality reductions and overdiagnosis during 2010-12 were computed without (scenario 1) and with (scenario 2) a cohort effect on mortality secular trends.
Results : The incidence of stage 2-4 breast cancers in women aged 50 or more was 168 per 100 000 in 1989 and 166 per 100 000 in 2012. Screening would be associated with a 5% mortality reduction in scenario 1 and with no influence on mortality in scenario 2. In both scenarios, improved treatments would be associated with 28% reductions in mortality. Overdiagnosis has steadily increased over time with the extension of screening to women aged 70-75 and with the introduction of digital mammography. After deduction of clinical lead time cancers, 33% of cancers found in women invited to screening in 2010-12 and 59% of screen detected cancers would be overdiagnosed.
Conclusions : The Dutch mammography screening programme seems to have little impact on the burden of advanced breast cancers, which suggests a marginal effect on breast cancer mortality. About half of screen detected breast cancers would represent overdiagnosis.
BMJ , article en libre accès, 2016