Re: No overdiagnosis in the Norwegian Breast Cancer Screening Program estimated by combining record linkage and questionnaire information in the Norwegian Women and Cancer Study

Abstract

The comment by Zahl [ [1] Zahl P.-H. Jørgensen K.J. Gøtzsche P.C. Re: No over-diagnosis in the Norwegian Breast Cancer Screening Program estimated by combining record linkage and questionnaire information in the Norwegian Women and Cancer study. Eur J Cancer. 2018; 97: 49-50 Abstract Full Text Full Text PDF Scopus (1) Google Scholar ] illustrates clearly the two different approaches in estimating overdiagnosis in the Norwegian Breast Cancer Screening Program. Zahl uses grouped data often named ecological data and mathematical models of underlying changes in risk to assess the association between participation in the screening programme and the potential for overdiagnoses. Owing to the potential for ecological fallacy, this kind of analyses is generally considered useful for generating hypotheses but not for testing hypotheses because of the large potential for biases or the ecological fallacy. On the other hand, our approach was to use personal information on the use of mammograms from questionnaires and register information on all screening participation over time [ [2] Lund E. Nakumara A. Thalabard J.-C. No overdiagnosis in the Norwegian Breast Cancer Screening Program estimated by combining record linkage and questionnaire information in the Norwegian Women and Cancer study. EJC. 2018; 89: 102-112 Abstract Full Text Full Text PDF Scopus (10) Google Scholar ]. Based on personal identification, this information was linked to the outcome of breast cancer through the Norwegian Cancer Registry. Most importantly, we could use the fact that there are three groups of women: participants in the screening, wild screened and never taken a mammogram. We neither assumed nor estimated any underlying distribution. We only counted cases of breast cancer in the different groups, calculated the person years and computed the cumulative risk or incidence. In addition, we could adjust for other breast cancer risk factors. No overdiagnosis in the Norwegian Breast Cancer Screening Program estimated by combining record linkage and questionnaire information in the Norwegian Women and Cancer studyEuropean Journal of CancerVol. 89PreviewThe Norwegian Breast Cancer Screening Program (NBCSP) was implemented across the country in 2005 and has been criticised for potential ‘overdiagnosis’, i.e. a breast cancer diagnosis that otherwise would not have been detected or treated in a woman's lifetime. We aimed to estimate overdiagnosis in the NBCSP based on the Norwegian Women and Cancer (NOWAC) study using both questionnaire information and record linkage information from NBCSP. Full-Text PDF Open AccessLetter comments on EJC published paper: ‘No overdiagnosis in the Norwegian Breast Cancer Screening Program estimated by combining record linkage and questionnaire information in the Norwegian Women and Cancer study’European Journal of CancerVol. 97PreviewIn a recent article, Eiliv Lund et al. argue that estimates of overdiagnosis is declining over time, and today, there is no overdiagnosis in the Norwegian Breast Cancer Screening Program [1]. Full-Text PDF