There is increasing evidence that digital breast tomosynthesis reduces the number of women recalled for further assessment (recall rate) and increases the number of breast cancers detected in population-based screening compared to standard digital mammography.
However, it is unclear whether detecting these additional cancers will reduce the number of breast cancers detected between screening examinations (interval breast cancers). It is possible that these additional cancers are slow-growing cancers that would never have caused symptoms and would have never been detected without participation in screening (overdiagnosis). This would be undesirable.
Researchers at the University of Sydney (Australia) will investigate this issue by combining data from studies performed in population-based breast cancer screening programs in Norway, Sweden and Italy.
The aim of their study is to use individual-level data to examine the interval cancer rates among women screened with tomosynthesis compared to standard mammography. They will also compare the rates of breast cancer detected through screening (screen-detected breast cancer) and recall rates associated with these two screening tools.
Data and project organisation
BreastScreen Norway will participate in this project by providing screening information from the Cancer Registry of Norway. These data include information about 140,000 women aged 50-69 who were screened in BreastScreen Norway in Oslo, Vestfold and Vestre Viken during 2014-2015, or in Bergen during 2016-2019.
Data will be provided to the University of Sydney in accordance with the Cancer Registry Regulations (kreftregisterforskriften). The project will only include data from women who have agreed to their personal data related to negative screening results being permanently stored at the Cancer Registry.
This study is registry-based, and women will not be contacted regarding the project. It will be impossible to identify individuals from any published study results.
The University of Sydney (Australia) is leading the project, and is responsible for checking, managing and analysing the collective data. They are also responsible for obtaining all approvals necessay to conduct this research in Australia.
The Cancer Registry of Norway is a project collaborator and is responsible for obtaining ethical approvals in Norway, as well as extracting, pseudonymizing and delivering data to the project.
Lund University (Sweden) and Azienda Provincale Servizi Sanitari (Italy) are also project collaborators. They are responsible for obtaining all necessary ethical approvals required in their countries, and for delivering data to the project from studies performed in their countries.
The University of Sydney has received all the Norwegian data (from Oslo, Vestfold and Vestre Viken in April 2020, and from Bergen in October 2020). They have also received the data from Sweden and Italy.
The project group in Australia has merged the data from BreastScreen Norway with screening data from Sweden and Italy. They are currently analyzing the data and published the first results early 2021.
Houssami N, Zackrisson S, Blazek K, Hunter K, Bernardi D, Lång K, Hofvind S. Meta-analysis of prospective studies evaluating breast cancer detection and interval cancer rates for digital breast tomosynthesis versus mammography population screening. Eur J Cancer. 2021 May;148:14-23. doi: 10.1016/j.ejca.2021.01.035. Epub 2021 Mar 9.
Houssami N, Hofvind S, Soerensen LA, Robledoc KP, Hunter K, Bernardi D, Lång K, Johnson K, Aglen CF, Zackrisson S. Interval breast cancer rates for digital breast tomosynthesis versus digital mammography population screening: An individual participant data meta-analysis. EClinicalMedicine 2021 Apr doi.org/10.1016/j.eclinm.2021.100804