Klinisk institutt 1

Midtveisevaluering- Hildegunn Aase

Hildegunn Aase er tilknyttet Klinisk institutt 1. Veiledere er Solveig Hofvind og Ingfrid Helene Salvesen Haldorsen

PhD project

Digital breast tomosynthesis - the future screening tool for breast cancer?


Screened women are in studies shown to have 40 % lower breast cancer mortality compared to non-screened women, still there were approximately 600 breast cancer deaths in Norway in 2017. Digital Breast Tomosynthesis (DBT) is a new screening tool. During a DBT-uptake the x-ray-tube is moving in a curve across the compressed breast, giving the impression of a 3D-image of the breast. The randomized controlled trial, the Tomosynthesis trial in Bergen (To-Be1), is aimed to compare early performance measures of screening with digital breast tomosynthesis included synthetic mammography (DBT) versus standard digital mammography (DM).

The trial was performed in Bergen during 2016-2017. 29 453 women aged 50-69 years attended. They were randomized to DBT or DM. Screening information was collected and the trial will be evaluated according to standard screening performance metrics and economical costs, DBT versus DM.

Hildegunn Aase, an experienced breast radiologist, started her PhD work on data from the trial early 2017. Aase’s PhD work will be related to different aspects of the To-Be trial, focusing on the radiological aspects.  

In the first study from the trial, an interim analysis after the first year, we found that DBT took longer to read than DM, but had significantly lower recall rate than DM. We found no differences in radiation dose between the two techniques.

Results from the two year period of the trial were recently published in the Lancet Oncology. Breast cancer detection did not differ significantly for women screened with DBT versus DM, but we observed lower consensus and recall rates for women screened with DBT. The distribution of histopathological tumour characteristics did not differ significantly between the techniques.

Another paper focusing on compression force used in DBT and DM in the To-Be trial is submitted for publication. The PhD student has been involved in all the publications, and has a first authorship on the first paper (1, 2).

The future PhD work will focus on mammographic features. We will also focus on time used for screen reading and screening volume for the individual radiologists in DBT and DM and explore possible factors of influence for the radiologists sensitivity of reading. Another aspect is early screening performance measures according to mammographic density.

At the moment, the PhD project is put on hold. Plans for continuation and finalization will be established during the spring 2020.

The trial is a collaboration project between the Cancer Registry of Norway, the Breast Centre at Haukeland University Hospital, the University of Oslo and the University of Bergen.  The study is approved by the Regional committees for medical and health research ethics (2015/424) and registered in Clinical trials.org (NCT02835625), and is funded with 12.5 million NOK by the Research Council of Norway.


1.            Aase HS, Holen AS, Pedersen K, Houssami N, Haldorsen IS, Sebuodegard S, et al. A randomized controlled trial of digital breast tomosynthesis versus digital mammography in population-based screening in Bergen: interim analysis of performance indicators from the To-Be trial. European radiology. 2018.

2.            Hofvind S, Holen ÅS, Aase HS, Houssami N, Sebuødegård S, Moger TA, et al. Two-view digital breast tomosynthesis versus digital mammography in a population-based breast cancer screening programme (To-Be): a randomised, controlled trial. The Lancet Oncology. 2019.