Transitioning from 2D digital mammography to 3D tomosynthesis: should we all consider making the switch?

The recently published article titled “Tomosynthesis vs digital mammography screening in women with a family history of breast cancer” compared the performance of digital breast tomosynthesis (DBT) versus digital mammography (DM) in women with a family history of breast cancer (1). It found that in a large cohort of 208,945 women with a family history of breast cancer, DBT screening reduced recall rates and increased specificity compared to DM, particularly in women with a first-degree relative with breast cancer and those with scattered fibroglandular density, as well as reduced advanced cancer in women with extremely dense breasts.

With this study adding a further piece of evidence for DBT in a subgroup of patients and we think it is timely to consider what evidence we have so far for DBT along with the practical challenges for making the switch from DM to DBT.

Early studies on the addition of DBT to DM alone showed favourable results for DBT. These include two prospective single-site European studies. Skaane et al. (2) reported a 40% increase in detection of invasive cancers with a simultaneous 15% reduction in false-positive results in 12,621 screening examinations.

In an analysis of 7,292 screening examinations, Ciatto et al. (3) demonstrated a significant increase in cancer detection rate (CDR) from 5.3 to 8.1 cancers per 1,000 women screened, with 20 of 59 cancers seen only after addition of DBT to DM.

Meanwhile, Friedewald et al. (4) reported a 41% increase in breast cancer detection, a 49% increase in positive predictive value (PPV) for recall, a 21% increase in PPV for biopsy, and a 15% reduction in recall rate.

Since then, there have been several published meta-analyses which have included a multitude of pooled studies and millions of patients.

Marinovich et al. (5) analysed seventeen studies with 1,009,790 participants in total. The pooled incremental CDR for tomosynthesis was 1.6 cancers per 1,000 screens. The recall rate for tomosynthesis was statistically significantly lower than for 2D mammography (pooled absolute reduction =−2.2%). Stratified analyses showed greater improvement in CDR in European/Scandinavian studies (biennial screening) and reduction in recall in United States (US) studies with high baseline recall.

Alabousi et al. (6) considered the addition of synthesized mammographic (SM) views in the analysis. Forty-two studies reporting on 2,606,296 patients (13,003 breast cancer cases) were included. CDR was highest in combined DBT and DM (6.36 per 1,000 screened), and combined DBT and SM (7.40 per 1,000 screened) compared with DM alone (4.68 per 1,000 screened). Recall rate was lowest in combined DBT and SM (42.3 per 1,000 screened).

Phi et al. (7) compared the accuracy of DBT and DM in women with mammographically dense breasts in screening and diagnosis.

Sixteen studies were included (five diagnostic and 11 screening). In diagnosis, DBT increased sensitivity (84–90%) versus DM alone (69–86%) but not specificity. DBT improved CDR versus DM alone [risk ratio (RR): 1.16]. In screening, DBT + DM increased CDR versus DM alone (RR: 1.33 for retrospective studies; RR: 1.52 for prospective studies). Recall rate was significantly reduced by DBT + DM in retrospective studies (RR: 0.72) but not in two prospective studies (RR: 1.12).

Zeng et al. (8) compared the screening performance of SM plus DBT with DM plus DBT or DM alone.

Thirteen studies involving 1,370,670 participants were included. Compared with DM/DBT, screening using SM/DBT had similar breast CDR [risk difference (RD) =−0.1/1,000 screens], but lower recall rate (RD =−0.56%) and lower biopsy rate (RD =−0.33%). Compared with DM, SM/DBT improved CDR (RD =2.0/1,000 screens) and reduced recall rate (RD =−0.95%). The conclusion was that SM/DBT could replace DM/DBT in breast cancer screening to reduce radiation dose.

Li et al. (9) performed a meta-analysis to pool incremental CDR and recall rate for DBT (versus DM) for high- and low-density [dichotomised based on Breast Imaging Reporting and Data System (BI-RADS)] and within-study differences in incremental estimates between high- and low-density. Screening settings (European/US) were compared. Pooled within-study difference in incremental CDR for high- versus low-density was 1.0/1,000 screens. Estimates were not significantly different in US and European settings. Pooled incremental recall was less in high- versus low-density in US screening, and greater in European screening. They concluded that DBT has differential incremental cancer detection and recall by breast density. Although incremental CDR is greater in high-density, a substantial proportion of additional cancers is likely to be detected in low-density screens. These findings may assist screening programmes considering DBT for density-tailored screening.

Despite the scientific evidence, there are still recent studies [Henderson et al. (10)] from population screening showing a large proportion of the screening population in some countries still having two-dimensional (2D) mammography. As a result, we consider the practical obstacles to making the switch.

Availability

Online search shows over 10 different manufacturers with provision of three-dimensional (3D) machines. Access to information on DBT has been complemented by educational events, seminars, conferences, and workshops with users sharing their experience. These initiatives have increased radiologists’ confidence in adopting this “new” technology.

Cost considerations

Moger et al. (11) analysed cost differences between DBT and DM in a breast cancer screening programme: results from the To-Be trial in Norway. This randomised controlled trial included 29,453 women and allowed for a detailed comparison of procedure use and screening, recall and treatment costs estimated at the individual level. The increased cost of equipment, examination and reading time with DBT versus DM was €8.5 per screened woman. Costs of DBT remained significantly higher after adding recall assessment costs, €6.2.

Bonafede et al. (12) performed value analysis of DBT for breast cancer screening in a commercially-insured US population. Base-case analysis results show that 4,523 women in the hypothetical million-member health plan who are screened using DBT avoid the use of follow-up services. The overall benefit of DBT was calculated at $78.53 per woman screened. Adjusting for a hypothetical $50 incremental cost of the DBT examination, this translates to $28.53 savings per woman screened, or $0.20 savings per member per month across the plan population and an overall cost savings to the plan of $2.4 million per year. They concluded that this study demonstrates clinical and economic favourability of DBT for breast cancer screening among commercially-insured US women.

Radiation dose

The first generation of DBT machines delivered higher radiation doses when added to DM. However, subsequent development of technology allowing SM views omitted the further acquisition of DM views. Radiation dose of DBT compared to DM still varies between studies in the literature, with some such as Gennaro et al. (13) showing a modest increase in dose with DBT and others such as Choi et al. (14) showing a lower dose with DBT compared to DM.

Tolerability of DBT

Saunders et al. (15) and Fornvik et al. (16) demonstrated that lower compression force can be used with 3D mammography without compromising diagnostic image quality, and reduced compression is associated with lower anxiety and pain levels.

Availability of DBT-guided biopsy

Biopsies performed with DBT guidance required less time and had fewer exposures than biopsies performed with DM guidance, without a significant difference in the initial or final malignancy rate or in the rate of high-risk lesion upgrade [Nguyen et al. (17)].

Availability of artificial intelligence (AI) for DBT

Recently launched 3D AI (Genuis AI from Hologic and Lunit INSIGHT DBT) can rapidly identify lesions with a single click to the area of concern, even within large image stacks. AI can be used as a “second reader” in centres with double reading despite a shortage of radiologists.

Reading time

With appropriate training, experience, and AI support, reading time should not be a significant issue for radiologists. Partridge et al. [2024] (18) showed that there was a short learning curve effect with readers showing significant improvements in reading times within the first 9 months of DBT experience.

Convincing referrers and end users

Many of the abovementioned factors are inextricably linked. For example, the authors of the current study mentioned in their discussion that showing benefit of DBT in patients with a family history of breast cancer may help convince insurance companies to provide reimbursement for DBT in this subgroup of patients. With reimbursement and higher referral numbers, the cost of investing in DBT equipment may be more acceptable for mammography centres.

Having higher CDR, lower radiation doses and acceptable cost of DBT may persuade health screening doctors to refer patients for DBT. The patients who have then undergone a DBT examination may find it more tolerable than DM, with fewer recalls, which may persuade friends and family members to use DBT for their screening.

Radiologists who have used DBT and gone through the learning curve may gain increased confidence in mammographic reading. They may then teach the modality to their junior peers and trainees and also show cases of DBT at meetings and tumour boards, which may convince clinical colleagues to refer patients for DBT.

In summary, there is already a wealth of published literature in favour of DBT and continues to be valuable studies such as this one evaluating DBT benefit in subgroups of patients. On a practical front, increased availability, technological advancements in dosimetry, availability of DBT-guided intervention and AI in DBT are recent factors which may further persuade those still using DM to make the switch.

Ultimately, the decision depends on individual centres. On one hand, a centre providing opportunistic breast screening and clinical breast assessment in a healthcare system which reimburses for DBT and an educated population of patients receptive to the scientific evidence may find it easier to switch to DBT when their DM machine is due for replacement. On the other hand, a district providing population screening may face more challenges in converting all their DM machines to DBT in terms of cost, training their technologists and radiologists in the use of the technology and persuading the population at large to undergo DBT. In this instance, scheduled implementation over a longer period of time may be needed.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Breast Communications. The article has undergone external peer review.

Peer Review File: Available at https://bc.amegroups.com/article/view/10.21037/bc-26-0004/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://bc.amegroups.com/article/view/10.21037/bc-26-0004/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

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