6 July 2015
Authors : Harding C, Pompei F., Burmistrov D., et al.
JAMA Intern Med. Published online July 06, 2015. doi:10.1001/jamainternmed.2015.3043
The objective of this study is to try to measure the benefits and harms of breast cancer screening during the year 2000 with a 10-year follow-up, as is carried out in the USA (women over 40 years of age), by comparing data from different counties regarding screening intensity, breast cancer diagnoses, breast cancer mortality, mastectomies. It was carried out on 16 million women and 53207 patients diagnosed with breast cancer.
In counties where screening is more intensive, it is found:
- an increase in the number of breast cancer diagnoses (+16% for a 10% increase in participation in screening), mainly by tumours smaller than 2 cm.
- no reduction in breast cancer mortality
- no reduction in the number of advanced breast cancers
- no reduction in mastectomies.
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These data are difficult to link with effective mammography screening, where the increase in small breast cancers must be accompanied by a decrease in advanced cancers and breast cancer mortality.
The most likely explanation is that the numerous small cancers detected by systematic mammography are essentially over-diagnoses, i.e. tumors that are not or are very slowly progressive, or spontaneously regressive, whose diagnosis is useless and harmful, whereas screening would not (or rarely) allow a better prognosis for progressive cancers.
Breast cancer mortality in organised mammography screening in Denmark: comparative study » BMJ 2010;340:c1241 http://www.bmj.com/content/340/bmj.c1241
This is a study whose level of evidence is limited by its nature (individual data are not known), but supported by its large size (16 million women), as well as by the additional analyses carried out by the authors.
The trials on which the organized screening of breast cancer by mammography is based are old, and their conclusions (fragile, moreover, because of certain biases and inconsistencies that have since been revealed ) cannot be applied to the current situation.
In conclusion, the study confirms the lack of effectiveness of breast cancer screening as found in other studies, including in Europe. , , ,,,
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