My colleague Brian Maher from Technology Insights recently wrote the following article on breast imaging technologies that I thought would be of interest:
Each year, after reviewing high-impact publications and findings from major clinical conferences, my research team and I like to reflect on the key imaging technology trends we've seen across the past year, and forecast how many of these trends will impact the provision of imaging services in the future.
One trend which continues to amaze us is the ever-increasing number of modalities which can be deployed at various stages in the breast cancer imaging pathway. From screening to diagnosis, from staging and pre-surgical planning to treatment monitoring, over a dozen different modalities are jockeying for position. Presently, 2D digital mammography, ultrasound, and breast MRI are considered to be "must have" technologies, representing the accepted clinical standards for various indications. However, while each of these modalities has a distinct and validated role in the care pathway, they also have their respective shortcomings, which are clinical and/or operational in nature.
Since our return from the 2010 RSNA, we've been contemplating what the "breast imaging center of the future" will look like with respect to technology. Will a new generation of breast imaging technologies supplant the incumbents? Here, we examine three key technologies making a strong claim for the future: 3D tomosynthesis, molecular breast imaging, and positron emission mammography.
Tomosynthesis: An Emerging Game-Changer?
In what will likely be one of the most disruptive technologies to be introduced in recent years, digital breast tomosynthesis has the potential to revolutionize screening and diagnostic mammography. Acquiring three-dimensional, tomographic views of the breast, radiologists can scroll through ultra-thin sections of the breast, allowing greater opportunity to detect small, less easily identifiable cancers. Continued clinical research indicates tomosynthesis can find incremental cancers over traditional 2D digital mammography, and has also demonstrated significantly lower recall rates - representing major clinical advantages over standard screening and diagnostic methods.
And yet, digital breast tomosynthesis is not without its challenges. While FDA approval for the first 3D tomosynthesis - Hologic's Selenia Dimensions system - may be only a few months away, several questions remain unanswered. Will it be used for screening, diagnosis, or both? Will radiation dose be at least similar to that of digital mammography? How will radiologists accept likely longer interpretation times? And lastly, will CMS or commercial payers provide incremental reimbursement, as they did with digital mammography when it first became available? Also, competing mammography-based technologies are expected to become available soon as well, such as GE Healthcare's contrast-enhanced spectral mammography and dual-energy mammography, and it is unclear how well-received these technologies will be relative to tomosynthesis.
Many institutions at the moment are lining up to become the first adopters of this system, and as Hologic already has numerous installations of the 2D-approved Dimensions system, a sizeable install base already exists which can be easily upgraded to 3D tomosynthesis capability. But, at a cost of over $420,000 (nearly a $100,000 increase over standard digital mammography systems), and without assurance of increased reimbursement, an investment in tomosynthesis may not be for all institutions, at least for now. However, for the "breast center of the future" seeking to provide cutting-edge mammography services, digital breast tomosynthesis could be considered a "must have" technology.
MBI: Demonstrating Value at Earlier Stages
Mammograms, ultrasounds, and MRI scans, though utilizing intrinsically different technology to image the breast, are all similar in that they collectively generate a detailed evaluation of breast anatomy, allowing providers to accurately locate abnormalities. However, a common challenge of anatomical breast imaging is the difficulty to distinguish benign tissue from malignancy, which often correlates to lower exam specificity and a higher number of false positives upon biopsy. In that regard, the ability to acquire functional information, detecting abnormal metabolic activity in breast tissue, is gaining broader clinical traction owing to greater confidence in differentiating benign tissue and malignancy.
Molecular breast imaging (MBI), as defined by a new class of breast-specific nuclear imaging technologies, strives to do just that. Utilizing technetium-based radioisotopes, MBI technologies detect areas of increased cellular metabolism suggestive of cancer. To date, MBI has predominantly been utilized as a secondary diagnostic aid, following inconclusive diagnostic mammograms or ultrasounds. Early adopters of MBI systems have used them both as alternatives and adjuncts to breast MRI. Now, new research presented at the 2010 RSNA suggests MBI may be used not only for secondary diagnoses, but also as a screening adjunct to mammography for patients with a high pre-test risk of breast cancer. Continued research suggests the ability to detect more difficult cancers, such as DCIS, with improved diagnostic performance for these types of patients. Moving forward, MBI will likely play a greater role in the complete diagnostic pathway for breast cancer patients.
Historically, only two vendors, Dilon Diagnostics and Gamma Medica, developed MBI systems, with key differences between the models being the number of detectors and detector material (single-head, sodium-iodide detector for Dilon's breast-specific gamma imaging system, and single- or dual-head, CZT detectors for Gamma Medica's LumaGEM system). But now, GE Healthcare has developed an MBI-based system similar to Gamma Medica's, further validating the role of MBI in care pathways, and likely paving the way for more evidence accumulation through GE's substantial distribution channels. Accordingly, in outfitting a "breast center of the future", MBI could serve as a differentiating technology to improve diagnostic capabilities earlier in the pathway, but more evidence will be needed to further clinically validate the technology and the different options available now and in the future.
PEM: Now a Viable Alternative to MRI
Acquiring functional information of breast tissue also has value at different stages in the breast cancer pathway. Once a tissue sample is confirmed to be cancer, the next decision-point for providers is to determine if there is additional cancer in the same or opposite breast which may have been missed by earlier imaging studies. Additionally, once this decision has been made and the appropriate course of therapy initiated, it is also necessary to monitor how well the treatment is progressing. Breast MRI has predominantly been utilized in this pre-surgical planning role owing to its very high sensitivity in detecting occult cancers missed by other modalities, and as a non-irradiating modality, demonstrates value in treatment monitoring. Despite its benefits, however, breast MRI is a very complex study for both radiologists and surgeons to interpret, is prone to false positives which can result in unnecessary biopsies - or worse - surgeries, and is often not well-tolerated by patients due to contraindications, claustrophobia, or body habitus.
To that end, positron emission mammography (PEM) - a unique modality developed by Naviscan - has often been considered an attractive alternative to breast MRI for pre-surgical planning and treatment monitoring. PEM, like MBI technologies, acquires functional information of the breast, but differs from MBI in that a specialized, breast-specific PET detector is used to measure the uptake of FDG, the most common and well-validated radiotracer used for tumor PET imaging. Areas of the breast suggestive of malignancy will appear brighter due to increased glycolysis relative to healthy tissue. The end result is a series of images, acquired in the same views at traditional mammography, which are relatively straightforward for radiologists and surgeons to interpret when compared to the hundreds, if not thousands, of images generated by breast MRI.
However, clinical research to date has not empirically stated whether PEM technology can stand on its own or serve as an adjunct to MRI. Now, with a landmark study published just prior to the 2010 RSNA and receiving considerable attention at the conference itself, it is apparent PEM can serve as a standalone alternative to breast MRI in pre-surgical planning, especially for patients who cannot tolerate the MRI exam. Published in the journal Radiology, investigators in a multi-center, randomized trial compared breast MRI and PEM in 388 patients (those who completed the study) with diagnostically-proven ipsilateral breast cancer to determine how well the technologies perform in detecting additional cancers in the same breast missed by other previous imaging. Overall, PEM demonstrated significantly higher specificity than breast MRI, and comparable sensitivity to MRI, and for those patients who did not have additional cancer in the same breast, PEM had a significantly higher positive predictive value of the biopsy, suggesting fewer unnecessary biopsies may be possible with PEM than MRI. Additionally, PEM and MRI together improved cancer detection capabilities than with MRI alone. Of note, however, MRI performed better than PEM at detecting present cancers at the lesion-, as opposed to breast-level, and proved to be more accurate than PEM in determining the width of excision and need for mastectomy.
Taken together, the study is very important for the future of PEM, suggesting PEM can serve as the "go to" modality for patients who cannot well tolerate an MRI scan, but also that PEM and MRI together can synergistically improve outcomes. The study also paves the way for future research determining how PEM will perform for other indications, such as during neoadjuvant therapy to determine immediate tumor response, as well as longer-term treatment monitoring. For imaging providers, PEM now has more ground to stand on relative to breast MRI, and in planning for the "breast center of the future", PEM may become an increasingly attractive modality given not only its performance, but also its small footprint, consistent reimbursement from Medicare, and positive acceptance by both patients and surgeons.
Determining "Best Fit" for Next Generation Technologies
With the multitude of new breast imaging technologies currently available or becoming available in the future, it will be increasingly difficult to determine which technology will be most appropriate for a given hospital, breast center, or imaging center. As you can see from above, the three modalities we highlight - tomosynthesis, MBI, and PEM - serve largely different roles in the breast cancer pathway. However, the roles are beginning to blur for some, and with the emergence of tomosynthesis, greater confidence in lesion detection earlier in the care pathway may inflect the downstream use of MBI and/or PEM.
Of note, not all of these technologies will be appropriate for the institution with capital to spend. Knowing the dynamics of the patient population, performance characteristics of existing breast imaging services, and strategic vision of the organization will be imperative in determining future roles for tomosynthesis, MBI and/or PEM at the organization. Additionally, new research is continually being published comparing these modalities to established ones, and likely in the future, to each other., As such, administrators and physicians must stay vigilant in following this rapidly evolving terrain for next generation breast imaging technologies.