International pooled study: Interval cancer with tomosynthesis in mammography screening

An international pooled study that will investigate whether tomosynthesis is a better screening technique for breast cancer than standard digital mammography.

About the project

Summary

The purpose of this study is to examine whether the use of tomosynthesis (3D) in mammography screening will improve the sensitivity of mammography screening, compared to the use of digital mammography (2D). We will base our analysis on individual screening data and use meta-analyses to stratify the results based on age and breast density. Meta-analyses are necessary because the interval cancer rate is so low that data from multiple studies must be combined to achieve sufficient statistical power to interpret the results.

Background

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 (BreastScreen Norway), Sweden and Italy.

Objective

The aim of this study is to use individual-level data to examine the interval cancer rates among women screened with tomosynthesis compared to standard mammography. The study will also compare the rates of breast cancer detected through screening (screen-detected breast cancer) and recall rates associated with these two screening tools.

Study implementation

BreastScreen Norway will participate in this project by providing screening information from the Cancer Registry of Norway at the NIPH. These screening 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, and in Bergen during 2016-2019.

Screening data, including information about breast cancer diagnosis, is linked to the individual woman`s participation in BreastScreen Norway.

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.

Data and project organisation

The University of Sydney (Australia) is leading the project, and is responsible for quality assurance, administration and analysing the pooled database. They are also responsible for obtaining all approvals necessary 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 group in Australia.

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.

Status

The University of Sydney received all the Norwegian data in 2020. The project group has published three scientific papers:

Status

The project is completed.

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