Research
Effectiveness of and overdiagnosis from
mammography screening in the
Netherlands: population based study
BMJ 2017; 359 doi: https://doi.org/10.1136/bmj.j5224 (Published 05 December 2017) Cite this as: BMJ 2017;359:j5224
Response:
Re: Effectiveness of and overdiagnosis from
mammography screening in the Netherlands: population
based study
Autier and colleagues [1] state that the Dutch breast cancer screening program seems to have little effect on the burden of advanced breast cancers and a marginal effect of mortality. They based their conclusions on aggregated data on breast cancer incidence by stage by five year age groups per year which they obtained from the Netherlands Cancer Registry (NCR) [2]. However, to evaluate the effect of the screening program on the rate of advanced-stage breast cancer, it is necessary to link data on tumour stage with individual level data on attendance to the screening program. For this a linkage is needed between the NCR and the data of the screening organisation. This linkage is regularly performed and analysed anonymously to support the evaluation and monitoring of the Dutch screening program. Without knowing which breast cancers were diagnosed in women attending the screening program, and which were not, it is not possible to accurately evaluate the effect of the screening program.
Furthermore, the overall (background) incidence in the Netherlands was expected to increase over time [3]. A stable incidence of advanced stage cancers could also be interpreted as a relative reduction, assuming an increase in the underlying breast cancer incidence. This brings us to another factor which should be kept in mind interpreting the findings of Autier et al. In his study advanced stage was defined as stage 2-4, which is quite wide-ranging for an evaluation on shifts in stage due to a screening program. Regarding tumour size, stage 2 can consist of invasive tumours of all sizes. [4]. Shifts in size within this stage could have been missed due to the wide-ranging definition Autier et al. used in their analysis. Even a small reduction in size could result in less burden for the patients, higher quality of life and better aesthetic results of therapy.
1. Autier P, Boniol M, Koechlin A, et al. Effectiveness of and overdiagnosis from
mammography screening in the Netherlands: population based study. BMJ 2017;359:j5224. 2. The Netherlands Cancer Registry. Cijfers over kanker (viewed 11 December 2017).
http://www.cijfersoverkanker.nl/?language=en
3. Louwman WJ, Voogd AC, van Dijck JAAM, et al. On the rising trends of incidence and prognosis for breast cancer patients diagnosed 1975–2004: a long-term population-based study in southeastern Netherlands. Cancer Causes & Control 2008;19(1):97-106.
4. Sobin LH, Gospodarowicz MK, Wittekind C. TNM Classification of Malignant Tumours, Seventh edition. New York: Wiley-Blackwell, 2009.
Competing interests: No competing interests
16 December 2017
Linda de Munck Researcher
Sabine Siesling, professor
Netherlands Comprehensive Cancer Organisation Utrecht, The Netherlands
