Veel vrouwen worden onnodig behandeld voor borstkanker*
Volgens een Deense studie is een op de drie gevallen van borstkanker die worden opgespoord via preventief onderzoek ongevaarlijk en leidt niet tot ziekte of dood. In deze gevallen zijn operatieve ingrepen en bestralingen overbodig. Doch preventief onderzoek naar kanker zorgt ervoor dat dodelijke vormen van kanker in een vroeg stadium worden opgespoord doch bestaat er echter een duidelijk keerzijde, namelijk overdiagnose en overbodige ingrepen. Dat is volgens de wetenschappers overigens bijna onvermijdbaar, aangezien het voor een arts moeilijk is om gevaarlijke en ongevaarlijke kankertumoren te onderscheiden. De wetenschappers o.l.v.
Jørgensen deden hun bevindingen op basis van een vergelijkend onderzoeken naar het effect van preventieve programma's tegen borstkanker in Groot-Brittannië, Canada, Australië, Zweden en Noorwegen.
Overdiagnosis in publicly organised mammography screening programmes: systematic review of incidence trends
Karsten Juhl Jørgensen, researcher, Peter C Gøtzsche, director
1 The Nordic Cochrane Centre, Rigshospitalet, Dept 3343, Blegdamsvej 9, DK-2100 Copenhagen, Denmark
Correspondence to: K J Jørgensen kj@cochrane.dk
Objective To estimate the extent of overdiagnosis (the detection of cancers that will not cause death or symptoms) in publicly organised screening programmes.
Design Systematic review of published trends in incidence of breast cancer before and after the introduction of mammography screening.
Data sources PubMed (April 2007), reference lists, and authors.
Review methods One author extracted data on incidence of breast cancer (including carcinoma in situ), population size, screening uptake, time periods, and age groups, which were checked independently by the other author. Linear regression was used to estimate trends in incidence before and after the introduction of screening and in older, previously screened women. Meta-analysis was used to estimate the extent of overdiagnosis.
Results Incidence data covering at least seven years before screening and seven years after screening had been fully implemented, and including both screened and non-screened age groups, were available from the United Kingdom; Manitoba, Canada; New South Wales, Australia; Sweden; and parts of Norway. The implementation phase with its prevalence peak was excluded and adjustment made for changing background incidence and compensatory drops in incidence among older, previously screened women. Overdiagnosis was estimated at 52% (95% confidence interval 46% to 58%). Data from three countries showed a drop in incidence as the women exceeded the age limit for screening, but the reduction was small and the estimate of overdiagnosis was compensated for in this review.
Conclusions The increase in incidence of breast cancer was closely related to the introduction of screening and little of this increase was compensated for by a drop in incidence of breast cancer in previously screened women. One in three breast cancers detected in a population offered organised screening is overdiagnosed.
© Jørgensen et al 2009
(Juli
2009)
