Should digital breast tomosynthesis vs. digital mammography be used in organised screening programmes for early detection of breast cancer in asymptomatic women with high mammographic breast density detected in a previous screening exam?

The GDG agreed that the balance between the desirable and undesirable effects favours the use of DBT. The overall certainty of the evidence is low because of the uncertainty in estimates for interval breast cancers and false positives, and the absence of data for the downstream impact on breast cancer mortality. 

The evidence shows that when using DBT, there are likely greater number of breast cancers detected. In addition, there may be less overdiagnosis when using DBT since a higher proportion of invasive breast cancers are detected compared with non-invasive ductal carcinoma (DCIS) which are clinically less relevant cancers. Interval breast cancers (detected between regular screening visits) may also be reduced. These moderate benefits probably outweigh the higher number of false positives that may occur with DBT.  

There are moderate costs associated with DBT over DM, which could increase health inequities if implemented, but there are fewer women with high breast density in the target population for screening. Implementation of DBT would be facilitated by increased availability of DBT machines, adequate human resources (radiologists and technical personnel), and financial resources.

Potential challenges may exist: 

• The need for an infrastructure to archive data on breast density from previous screening exams and to share mammograms across centres as well as alerting that a woman with high breast density during the screening is required.
• The use of DBT might increase the overall time for reading mammograms (either due to an increased time for reading a single mammogram or due to the necessity for the radiologist to rest between reading different mammograms).
• In some countries, difficulties in recruiting radiologists for screening programmes exist.
• Referring women to another centre equipped with DBT might be not acceptable in certain countries.

Use of artificial intelligence (AI) algorithms might help overcome some challenges (please refer to the specific ECIBC recommendations on the use of AI in screening). 

A validated approach to assess breast density objectively will facilitate implementation. 

Quality assurance and improvement will be challenging given the need to divide women between the first or previous detection of high breast density.

Feasibility and acceptability could be assessed in the monitoring of programmes. Quality control procedures and quality standards should be further developed. Standards should be developed in particular for the image quality of synthesised 2D images from the tomosynthesis technology.

• Further research is needed to identify which high density group experiences the greatest net desirable consequences.
• There is a need for research examining the classification of mammographic breast density and standardisation of the classification systems used for breast density, including technology for the automation of the determination of breast density. Research should also aim at establishing the appropriate density threshold for changing imaging techniques.
• Further research is needed to build the evidence on benefits and harms of DBT vs DM through comparison of direct outcomes, including impacts of interval cancer incidence, stage of breast cancer at detection, and mortality reduction.
• There is also a need for research evidence on repeated DBT examinations since the current evidence is mainly restricted to a single surveillance episode.
• Further research should also assess the cost-effectiveness implications of tailored DBT screening for high mammographic breast density.
• Additional research should also assess the comparison between DBT and DM plus ultrasound for dense breast screening.
• Research is needed to define the quality parameters that need to be fulfilled for DBT-based breast cancer screening programmes to be implemented.