All women should get regular mammograms, but what about those at elevated risk? Radiologist Kimberly Ray, MD, presents this quick update to ensure timely supplemental screening practices and appropriate imaging decisions. She explains the “dense breast” conundrum, illustrating with images from a variety of technologies, and offers compelling data on the use of 3D mammograms and MRI. Bonus: See UCSF’s high and intermediate-risk screening guidelines.
So I am as a breast radiologist, I'm going to talk a little bit about high risk screening from the radiology perspective and see here. So just to put risk assessment into kind of broader context, I do think it's important to remember that the major risk factors for developing breast cancer are number one simply being female and number two increasing age. So we know that roughly three quarters of all breast cancers actually arise in women who don't have any family history and who are not otherwise considered to be high risk. Only about nine of breast cancer is hereditary. And um this is why we still recommend screening mammography for all women, not just those we perceive to be at elevated risk. Otherwise we missed the majority of breast cancers. And in order to maximize the mortality benefit, which is around 40%. Um we recommend annual screening mammography beginning at age 40. So the value of risk assessment is not to limit screening but rather to identify those women who are likely to benefit from supplemental screening above and beyond what we offered to women at average risk. So this includes screening at an earlier age as well as the use of advanced screening techniques. So candidate technologies include thomas synthesis, so called three D. Mammography as well as breast ultrasound. And these are an atomic based imaging techniques. And then we also have a magnetic resonance imaging MRI. Which is a hybrid um an atomic and functional technique as we'll see in a minute. So the achilles heel of conventional two D. Mammography is breast density. So there are four categories of breast density which we assess qualitatively and describing our mammography reports. And they're shown here from least to most dents. We know that demographic sensitivity decreases with increasing breast density and this is because the fiber glandular tissue attenuate X rays and appears white on the mammogram. But so does breast cancer. So white on white is hard to see now, even though breast density tends to decrease with increasing age, roughly half of all women undergoing screening mammography will have dense breast tissue. And so this is a problem that affects many women. The significance of breast density is twofold. So first there's a masking effect which can hide a breast cancer and therefore in women with dense breasts, we tend to see more integral cancers that present in between screening exams and these cancers tend to have a worse prognosis. The second issue is that breast density itself turns out to be a risk factor for the development of breast cancer. So a woman with the highest breast density uh has roughly two fold higher relative risk than a woman with average breast density. And this is equivalent to having a single first degree relative with breast cancer. So densities are risk factors that is now increasingly being incorporated into various risk assessment models, Thomas Synthesis, or so called three D mammography was developed specifically to overcome this limitation of rest density. So in a coma synthesis exam a series of low dose X ray images are obtained in an arc across the breast and the images are then reconstructed using a computer algorithm into a series of thin slices through the breast. And this reduces the masking effect of overlapping tissue Thomas Synthesis has been shown to increase cancer detection by roughly 30 and also to decrease false positive callbacks by about 15%. The greatest benefit has been shown for women with dense breast tissue as well as younger women, particularly those undergoing their baseline mammogram. That said all women stand to benefit to some degree from this technique, and thomas synthesis is likely to become the standard screening technique in the future. Here's an example of a very subtle cancer in a patient with dense breast tissue is barely visible on the two D. Mammogram your seen in close up. So this is a finding that's easily missed, particularly in a stack of screening films. However, on the corresponding thomas emphasis image, the mass is much more visible and you can see the fine margin speculation of this cancer. So this is a finding that much harder to miss and you can see how thomas synthesis can boost our sensitivity in dense breast tissue. Ultrasound is another technique that supplements mammography because it does not involve X rays. It's not limited by breast density. And while we use ultrasound routinely in the diagnostic setting, it's also been investigated as a supplemental screening tool in women with dense breast tissue. In studies of women with dense breasts who were at elevated risk of developing breast cancer, Ultrasound was shown to increase cancer detection by as much as 50 relative to mammography alone. However, this was also accompanied by a significant increase in the number of false positives. So the biopsy rate was double that of mammography alone and only 7-8 of biopsies yielded a cancer diagnosis. So the specificity of ultrasound is quite limited. Furthermore, the incremental benefit of of ultrasound decreases if women are already screened with thomas emphasis. So currently we do not offer whole breast screening ultrasound at UCSF primarily because of this concern over excessive false positives. Mhm. And finally we have breast of RI, which is the most powerful supplemental technique that we have available to us. Uh MRI requires a high field strength magnet and dedicated breast coil to provide high resolution images of the breast. The patient is imaged in the prone position, with her breast hanging dependent in the breast coil, there's no compression applied. However, we do need to inject intravenous gadolinium contrast for the exam. MRI provides true three dimensional images with high spatial resolution and good soft tissue contrast. Mhm memory is also in part a functional test because contrast enhancement reflects this property of tumor neurovascular charity and this um this feature of contrast enhancement is really the key to mris very high sensitivity for breast cancer detection because US enhance more rapidly and more rapidly than normal breast tissue. Rest density is not a limitation of MRI. Now in very high risk populations, mammography has been shown to have less than 50 sensitivity. So this is in part due to dense breast tissue in high risk patients who present at younger ages. In addition, biologically aggressive cancers may have a typical imaging features that may be subtle or occult at mammography. So we know that MRI has much higher sensitivity in these high risk populations. On the order of 70 200%. MRI detects small, no negative cancers and has been shown to lower the interval cancer rate to under 10 limitations of MRI include its relatively high cost and limited availability. In addition, there is limited specificity when it's applied to lower risk populations. In the last couple of minutes, I will just briefly review UCSF recommendations for high risk screening which are based on national guidelines. So for women who are at the highest risk, this includes Gene mutation carriers as well as their untested first degree relatives, as well as those women who have a calculated lifetime breast cancer risk of 20 or more based on various risk models that incorporate family history. We recommend annual screening mammography, preferably with Thomas synthesis beginning at age 30, as well as annual breast MRI beginning at age 25-30. And typically we will alternate mammography and MRI at six month intervals to ensure that we're looking at the patient every six months with one modality or another. Patients who've had chest radiation under the age of 30 are also at markedly elevated risk, beginning eight years after their treatment For these patients. We recommend annual mammography, preferably Thomas synthesis, beginning eight years after their radiation treatment, but not before age 30 And and and annual breast MRI beginning eight years after treatment, but not before age 25. Moving on to women who are intermediate risk. This includes those patients who have had a personal history prior history of breast cancer and either dense breast tissue or those who are diagnosed at a young age before age 50. For these patients who are treated with breast conserving surgery, we will perform diagnostic mammography of the affected breast every six months along with annual screening of the opposite breast for the first five years after completion of treatment. Subsequently recommend annual screening mammography in all cases, preferably with thomas synthesis in these patients. We also recommend annual MRI. In addition to mammography. Lastly also following into the intermediate risk category. Gory include patients who've had high risk lesions on breast biopsy, including L. C. I. S. Lobular carcinoma in situ as well as the https for these women, we recommend annual mammography, preferably thomas synthesis beginning at age of diagnosis. And consider adding annual MRI. If especially if there are other risk factors such as dense breast tissue as well as a family history of breast cancer.