Crisis or Opportunity?
Breast Density Notification, Workflow and the Implementation of Screening Ultrasound
Gerald R. Kolb
The world of breast imaging began a dynamic evolutionary process beginning in 2007, with the recognition that the traditional screening mammogram was not sufficient for all women, and that very high-risk women should also receive adjuvant-screening breast MRI.1 That process has seen the "one size fits all" screening protocol covering all women age 40 and older challenged by the USPSTF recommendations in 2009,2 and increased awareness of the clinical benefit of breast ultrasound when used to supplement screening mammography for women with dense breasts and normal mammograms.3,4,5,6
Paralleling the awareness of sensitivity issues with conventional mammography was the development and clearance of digital breast tomosynthesis (DBT), which has established new benchmarks for reducing recall rates for screening mammography and showing promise for increasing sensitivity, as reflected in higher cancer detection rates.7,8 Given the early findings from DBT studies, it is likely that a large scale multi-center trial will confirm some improvement in cancer detection rate, however tissue density can still be expected to affect x-ray attenuation, and thereby sensitivity, in some percentage of patients with dense tissu.
A complete discussion of the prospective studies that will be necessary to define and compare the respective contributions of DBT and whole breast or automated whole breast ultrasound is well beyond the scope of this paper. Breast screening is moving toward an individualized approach where each patient's screening strategy will be determined through the evaluation of causal risk and factors such as breast density to determine an optimal approach. The author believes strongly that the process of individualization should begin now, even though all of the information is not yet in as to what may be optimal. It is highly likely that basic screening will eventually be a combination of DBT and automated breast ultrasound, determined for each patient through objective analysis of risk and breast density. To wait for perfect knowledge, however, would be to deny valuable care to many women, and the purpose of this paper is to discuss how ultrasound can be utilized adjunctively for women with dense breast tissue. Screening ultrasound has problems, but the evidence supports its value in early detection for women with dense breast tissue.
Breast density notification is becoming a reality in many states across the US by virtue of legislation spurred on by dedicated advocates and interested breast radiologists. With supplementary screening potentially affecting 45% of the women who are screened each year, screening ultrasound becomes a disruptive technology. To be used effectively, therefore, its implementation requires a significant shift in the traditional delivery paradigm. This paper is intended to help the reader understand the workflow modifications and adaptations that are required to build an effective delivery platform for screening.
Both mammography and ultrasound have relatively low reimbursement, emphasizing the importance of efficient workflow. The volume of screening procedures has a leveraging effect on even small revenue or cost numbers, lending further emphasis to the importance of delivery design. As this article is developed, the reader is expected to conclude that changing the way screening is delivered is not only an economic imperative, it is the only practical way to deliver on the promise of early detection of breast cancer for women.
Before discussing workflow in a breast center, it is appropriate to review both the breast center itself, and breast density. A basic understanding of both will allow the reader to more quickly understand how the suggested changes will improve both patient care and breast center economics.
The operative term is screening. Because the screening patient is, by definition, asymptomatic, supplementary screening ultrasound for the patient with dense breasts is not the same as adding a diagnostic ultrasound in the case of a woman with abnormal findings. She is, in fact, a screening patient and the ultrasound is a part of that screening. From this perspective, the challenge becomes how to seamlessly provide both screening mammography and supplemental breast ultrasound for women with dense breasts without adding the inconvenience and cost of requiring women to return to the center at a later date for the ultrasound.
Offering supplementary screening ultrasound within the same visit envelope as the screening mammogram for the woman with dense breasts has two very practical benefits. First, providing the two procedures in a single visit has the economic benefit of eliminating the non-clinical costs of the second procedure (see the callout below.). In practice, these costs range from $25- $75,9 with the latter cost more typical of large organizations. Measured against global reimbursement that may only be $100-$200, savings of this order can be very significant.
Second, incorporating ultrasound in the screening visit rather dramatically increases compliance because it makes the supplementary exam convenient for the patient, even if she is required to pay for the additional procedure. Breast centers have often failed in the past to sufficiently consider the time demands on patients, and should not assume that a woman will return who is "called back" for another screening exam. An additional screening procedure is very different from a diagnostic recall - where the physician has identified an area of concern - and psychologically appears much more optional for women whose mammograms are normal. It is important to remember that density notification, in a recent study of compliance at a breast center in Santa Rosa, CA, the number of women opting for same day screening ultrasound was eight times the number who responded positively when recalled for the ultrasound procedure. This center utilized automated breast ultrasound and required the patient to pay for the exam.10
A detailed review of breast density is beyond the scope of this article, but there are a few important points that bear emphasis. The first of these is that breast density really means radiographic density, or the way the breast appears in a mammogram. Breast density cannot be felt or found in any way other than by imaging. On a mammogram, fatty tissues are transparent to x-rays, and therefore these tissues appear black on the image. Dense areas absorb x-rays and appear white on the image, but unfortunately cancers also absorb x-rays and therefore dense tissue can be confused with or hide breast cancers on the mammogram. There is also strong evidence that breast density is associated with an increased risk of breast cancer.11, 12
Radiologists have traditionally measured breast density by comparing light and dark areas of a mammogram, with breast density defined as the area of white tissue divided by the total area of the breast and expressed as a percentage. The BI-RADS™ density categories provide radiologists with the ability to describe the relative breast density, composition and the potential for missing a cancer due to the reduced sensitivity of the mammogram that is caused by density masking a breast cancer. The BI-RADS™ density categories provide a relative picture of density for referring physicians and other radiologists. BI-RADS 4th Edition describes the density categories as follows:13
- Category 1 The breast is almost entirely fat (<25% glandular).
- Category 2 There are scattered fibroglandular densities (approximately 25-50% glandular).
- Category 3 The breast tissue is heterogeneously dense, which could obscure detection of small masses (approximately 51% - 75% glandular).
- Category 4 The breast tissue is extremely dense. This may lower the sensitivity of mammography (>75% glandular).
The challenge with physician assessment of breast density is that such determination is subjective, operator dependent and entirely qualitative. According to a 2006 study in Academic Radiology, agreement between interpreting physicians in estimating density using the BI-RADS categories is only about 60 percent between the middle two BI-RADS density categories, which is also the differentiating line between low and high tissue density.14 The methodology for this study had three attending radiologists with one, five and ten years of mammography experience ascribing density findings using all four standard mammographic views. Participants were blinded to previous density assessments.
To support the use of supplemental imaging in a manner that reflects the evidence for its benefit, the subjectivity of physician assessment of density must be removed in order to give referring physicians and patients alike a sense of confidence in the density determination process. There are currently two FDA cleared, commercially available products that assess volumetric density and can be utilized to provide density assessment (Volpara® - Matakina International, Ltd., Wellington, NZ and Quantra™ - Hologic, Inc., Bedford, MA). Each of these software products provides an automatic and objective density assessment that can be delivered to the technologist in the mammography room following the mammogram, and is also sent to the interpretive workstation and PACS. The importance of this capability will become evident as workflow is discussed below.
This article began by using the term disruptive. The very act of informing the patient of her breast density is inherently disruptive, in that it raises questions with both the patient and her physician about what density means and what to do about it. In fact, other than the increased cancer detection rates experienced in Connecticut,1,2 the significant lesson of density notification in that state was confusion - confusion for both the patient and the referring physician. Breast density is not a well-understood concept outside of radiology and, when patients began calling their physicians with density questions, those physicians felt abandoned by radiology which, in large part, had provided little or no guidance or education on breast density and its implications to the referring physicians.
The prerequisite for dealing with breast density both with referring physicians and with patients is education. Even in states without legislation, it is important to educate referring physicians, patients as well as the breast center staff about the importance of breast density in individualizing a woman's breast care. Physician letters, grand round presentations, breast conference discussions, etc. are common methods of informing the medical staff about breast density. Brochures, posters and other aids are important in educating the patient. It is also important to recognize that breast density questions posed by patients to their primary care physicians will be problematic for those physicians from a time perspective. Anything that can be done by the breast center to alleviate this disruption is important. The technologist can perform an important role in this educational process.
There is little middle ground between notifying women of breast density and offering supplementary breast ultrasound, as it makes no sense to tell a woman her mammogram may be of little value and not offer a supplementary procedure. However, the prospect of adding a screening procedure for up to 45% of the screening mammography volume can be daunting!
From experience, it is recognized that not all women with dense breasts will opt for an additional screening procedure. It is likely that initial compliance will be from 15%-20% of those eligible, particularly if the woman needs to return to the breast center. The compliance rate should increase to 50%-75% over the first few years — if the breast center incorporates supplemental ultrasound [whether hand held or automated] into the screening paradigm in a patient-friendly manner as recommended below.
As described above, providing seamless screening workflow is both an economic necessity for the breast center, and a patient convenience imperative for the achievement of high compliance rates. To achieve seamless delivery, the screening schedule must be adjustable so that ultrasound exams can be added if indicated. If the patient's density is known in advance, a "double" appointment could be scheduled, but density changes over a woman's life and the need for ultrasound will change with that density. Having the support capability for add-on studies, similar to what many centers now do for diagnostic ultrasound, will allow a center to respond to the need for supplementary ultrasound. It will be a challenge at first, but the breast center will soon have a better gauge on demand. Special note: the author and others who have been involved with many breast centers have found that those centers that control their own scheduling are better able to achieve more flexibility in their operations, and this kind of flexibility is considered to be a success factor for achieving a seamless, efficient, and profitable multi-modality screening program.15
Who Should Receive the Supplementary Imaging Procedure?
Using one of the objective assessment tools referred to above - along with a protocol that recommends women with BI-RADS 3-4 density be advised of their density and offered the addition of ultrasound - allows the technologist to inform the patient, explain the importance of density and offer the additional screening service. Note that this process will also largely eliminate the need for patients to go back to their primary care physicians for recommendations.
Interpreting physicians will find that having both the mammogram and supplemental ultrasound available when reviewing the images of women with dense breasts will enhance speed and accuracy over reviewing the images separately. This is a change in the way the typical breast center operates and, as such, will require a period of adjustment, but all of the studies have indicated a very significant additional accrual of early, very treatable cancers.
Providing prompt, convenient and clinically effective service to women has long been the mission of breast centers. Informing women of the importance of breast density and moving to a screening protocol that includes ultrasound where necessary is a natural step in the evolution of that mission. Most importantly, this is something that can be implemented now to improve the health of the women we serve - and that is the reason for our existence.
Disclaimer: The author is the CEO of Ikonopedia, Inc., and is a consultant on clinical affairs to Matakina International, Ltd., the manufacturer of the Volpara® volumetric breast density assessment algorithm. For more information about how to incorporate screening ultrasound into the breast center's workflow, please contact him at firstname.lastname@example.org or +1 303.881.1012.
1 Saslow D, Boetes C, Burke W, et al. American Cancer Society guidelines for breast screening with MRI as an adjunct to mammography. CA Cancer J Clin. 2007;57:75-89.
2 United States Preventative Services Task Force. Screening for breast cancer: U.S. Preventive Services Task Force recommendation statement. Ann Int Med, 2009; 151:716-26.
3 Berg WA, Zhang Z, Lehrer D, et al. Detection of breast cancer with addition of annual screening breast ultrasound or a single screening MRI to mammography in women with elevated breast cancer risk. JAMA, 2012; 307(13):1394-1404.
4 Weigert J, Steenbergen S. The Connecticut experiment: The role of ultrasound in the screening of women with dense breasts. Breast J, 2012;18(6):517-22.
5 Hooley RJ, Greenberg KL, Stackhouse RM, et al. Screening US in patients with mammographically dense breasts: Initial experience with Connecticut Public Act 09-41. Radiology, 2012; 265(1):59-69.
6 Kolb TM, Lichy J, Newhouse JH, et al. Comparison of the performance of screening mammography, physical examination, and breast US and evaluation of factors that influence them: An analysis of 27,825 patient evaluations. Radiology, 2002; 225(1):165-75.
7 Skaane P, Bandos AI, Gullien R, et al. Comparison of digital mammography alone and digital mammography plus tomosynthesis in a population-based screening program. Radiology, 2013; 267(1):47-56.
8 Rose SL, Tidwell AL, Bujnoch LJ, et al. Implementation of breast tomosynthesis in a routine screening practice: An observational study. AJR, Am J Roentgen, 2013; 200(6):1401-8.
9 Personal experience of the author over 15-years of observation.
10 Private communication from Dennis McDonald, MD. Unpublished.
11 Boyd NF, Martin LJ, Bronskill M , et al. Breast tissue composition and susceptibility to breast cancer. J Natl Cancer Inst, 2010. 102(16):1224-37.
12 Boyd NF, Guo H, Martin LJ, et al. Mammographic density and the risk and detection of breast cancer. N Engl J Med, 2007; 356(3):227-36.
13 D'Orsi CJ, Bassett LW, Berg WA, et al. Breast imaging reporting and data system (BI-RADS): Mammography, 4th ed. Reston, VA: American College of Radiology; 2003.
14 Nicholson BT, LoRusso AP, Smolkin M, et al: Accuracy of assigned BI- RADS breast density category definitions. Acad Radiol 2006; 13:1143-49.
15 Lee CZ, Comprehensive breast centers: Priorities & pitfalls, The Breast Journal, 1999; 5(5):319-324.