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Taylor A. Johnson
Here at OncoBites, we have covered multiple advancements in the imaging and diagnosis of cancer. These have included isotonic labeling to detect the cancer progression, liquid biopsies for uncovering tumor profiles, and even artificial intelligence for interpreting images. In addition, several aspects of breast cancer, ranging from new therapies to health service interventions, have been highlighted. This piece will combine those two aspects and place the spotlight on imaging techniques used for breast cancer detection, with particular emphasis on the emerging use of digital breast tomosynthesis (DBT) as an alternative or complementary screening method.
Mammograms are the gold standard in breast cancer diagnosis. These two-dimensional x-ray images have shifted from being collected onto films to being stored on computers (digital mammograms; DM). Compared to traditional film-based mammography, DM is more accurate in diagnosing women under the age of 50, women with heterogeneously or extremely dense breasts, and pre-menopausal or perimenopausal women (1). If the results are unclear, follow up options include an additional mammogram or utilizing a complimentary non-radiation based technique such as sonography (sound wave based) or magnetic resonance imaging (MRI; magnetic field based).
In an effort to improve patient diagnosis, DBT has been explored as an alternative, more comprehensive method. DBT, like DM, utilizes low dose radiation to make an image; however, several images are taken (usually at 1 mm intervals) and ultimately uploaded into specialized software to reconstruct the breast and provide a three-dimensional perspective (2). This is achieved through 1) taking independent images around the patient’s breast (step-shoot method) or 2) taking continuous sweeping images (2, 3). There are several benefits to implementing DBT into regular breast cancer screening. The most obvious benefit is providing physicians multiple viewpoints of breast tissue to help determine whether the patient is developing breast cancer, the approximate location of the cancer, and the approximate size of the tumor. The use of DBT also allows for the reduction of any masking effects that may be caused by tissue overlap. In a study of 13 United States medical centers, the breast cancer detection rate increased by over 40% when using combined DBT and DM diagnosis compared to DM alone (4). A separate two year trial showed that the cancer detection rate was higher in patients who underwent both DBT and DM for primary breast cancer screening compared to DM alone (8.6 versus 4.5 per 1000 cases), as well as a reduction in false positives in the DBT/DM group (5). The combined use of DBT with DM increased cancer detection sensitivity and reduced false-positives by roughly 1/3rd, although the degree of decrease has been debated.
Unfortunately, there are some drawbacks to the use of DBT. Due to the implementation of an additional technique, patients are exposed to more radiation; however, the dose is still within safe limits. To lower the amount of time patients are exposed to radiation during imaging, one could also take the data collected from DBT testing and create 2D images as well, rather than taking both a traditional DM and DBT. The longer exposure time necessary for DBT also increases the likelihood that an image becomes distorted or errors arise during development (3). Lastly, DBT requires that the patient remain still longer for images to be properly taken. Collectively, this suggests the combined use of 2D/s2D and 3D imaging is ideal to provide patients and physicians with clearer information regarding potential breast cancer development.
The cost to conduct these tests is ever-present in medicine. Interestingly, one could argue that DBT could either increase or decrease cost (2). For example, costs could increase due to the necessity of new software, technology, and storage necessary to save the 3D images. However, if DBT were shown to diagnose breast cancer more quickly and effectively, then all parties would financially benefit. In addition, the design of the technique can reduce the likelihood of false-positives, which also benefits all parties.
Currently, there is an ongoing Phase III Clinical Trial designed to compare patients subjected to DBT and DM over the course of multiple years (NCT03233191). Several objectives of this trial include comparing recall rates and biopsy rates, assessing technique combinations to determine the optimum balance of diagnostic performance, radiation exposure and technique, and implementing a central quality control monitoring program. As it stands, 29 states, Puerto Rico, Argentina, and several locations throughout Canada are involved in this trial, with women between 45 and 74 years of age enrolled.
Although there is no uniform consensus regarding recommended age and number of checkups for breast cancer detection, there is some common ground. Organizations such as the American Cancer Society, the American College of Obstetricians and Gynecologists, and the Canadian Association of Radiologists recommend at least one annual screening in your 40’s, and between one to two screenings per year as you age. Hopefully in the near future, not only will there be a universal guideline, but also a clearer picture regarding the use of DBT in breast cancer detection.
Taylor Johnson, M.S. is a Biomedical Sciences Ph.D Student in the Department of Anatomy & Cell Biology at East Carolina University; Greenville, North Carolina.
1 – Pisano ED, Gatsonis C, Hendrick E, et al 2005. Diagnostic performance of digital versus film mammography for breast-cancer screening. New England Journal of Medicine. 353(17): 1773 – 1783.
2 – Michell MJ and Batohi B. 2018. Role of tomosynthesis in breast imaging going forward. Clinical Imaging. 73: 358 – 371
3 – Sujlana PS, Mahesh M, Vedantham S et al 2019. Digital breast tomosynthesis: Image acquisition principles and artifacts. Clinical Imaging. 55: 188 – 195.
4 – Friedewald SM, Rafferty EA, Rose SL et al 2014. Breast cancer screening using tomosynthesis in combination with digital mammography. JAMA 311: 2499 – 2507.
5 – Pattacini P, Nitrosi A, Giorgi Rossi P, et al 2018. Digital mammography versus digital mammography plys tomosynthesis for breast cancer screening: the Reggio Emilia tomosynthesis randomized trial. Radiology. 288: 375 – 385.