Supplemental Breast Cancer Screening and Tests for Patients with Dense Breast Tissue
Options for Supplemental Breast Cancer Screening
Among the additional tests that are available, screening breast magnetic resonance imaging (MRI) and screening breast ultrasound have been tested extensively. Background breast density has less impact on the ability of MRI and ultrasound to detect cancer than it does for mammography, which is why either of these tests increases cancer detection over mammography alone, MRI much more so that ultrasound. However, both MRI and ultrasound are associated with a much higher rate of benign biopsies and a much higher rate of recommendation for short interval follow-up than mammography. Therefore, choosing to have one of these tests in addition to mammography involves the benefit/risk trade-off of early cancer detection versus increased false positives. The higher the cancer risk, the more likely they will benefit, so the trade-off is more favorable for high-risk woman than for average-risk women who simply have dense breasts.
Screening breast tomosynthesis (3-D mammography) is currently available at multiple UH sites. Population-based screening trials indicate that tomosynthesis increases breast cancer detection similar to ultrasound (although not as much as MRI), and that tomosynthesis decreases the rate of false positives, even below that seen in screening mammography. Tomosynthesis has been shown to increase invasive cancer detection by 41 percent and decrease false positives by 15 percent. Increase in cancer detection is seen in 90 percent of the population (all breast densities except for almost entirely fatty breasts, seen in 10 percent of the population). There are CPT codes and CMS reimbursement for tomosynthesis as of January 1, 2015.
Supplemental Screening Test Recommendations
In high-risk women, supplemental screening tests are recommended in addition to mammography. Studies support the use of screening MRI in women who are known to have a very high risk of breast cancer (greater than 20 percent lifetime or greater than 5 percent 10-year), regardless of their breast density. This examination is widely recommended by radiologists and the American Cancer Society.
Other studies have provided support for screening ultrasound for high-risk women, but only for those women with dense breasts who have not had an MRI. If a woman has a screening MRI, screening ultrasound will provide no additional benefit. Although a more expensive test, screening breast MRI is generally covered for women who are at very high risk. There is no formal recommendation from the radiology community at this point regarding screening ultrasound. As of January 1, 2015, there is a CPT code and CMS reimbursement for screening breast ultrasound.
For women with dense breasts, a risk assessment may be helpful. For the great majority of women informed that they have dense breasts under the law, breast density itself has only a small impact on their overall risk. But there are other important risk factors that also may come into play, and knowing a specific patient’s risk level can help to determine whether supplemental screening is appropriate. If a woman is at very high risk, a screening MRI would likely be helpful.
If a woman requests supplemental breast screening, it may be possible to rapidly triage the need for a risk assessment. The strongest risk factors for breast cancer, other than age and sex, are personal or family history (especially a first degree relative with premenopausal breast or ovarian cancer), and personal history of atypia on prior biopsy (ADH, ALH, LCIS). While neither of these risks, nor dense breasts, individually place a woman in the very high-risk category, they may identify those who would likely benefit from a full risk assessment, using mathematical models such as Claus, BRCAPRO, Tyrer-Cuzick (IBIS Breast Cancer Risk Evaluation Tool), BOADICEA and others. This is best conducted by someone who is fully informed on risk assessment procedures and who can counsel the patient on the results. Clinicians who feel comfortable in this capacity can perform a risk assessment, or refer on to a cancer risk assessment program such as the Center for Breast Cancer Prevention at University Hospitals Seidman Cancer Center.
For patients who have had mantle radiation therapy under age 30 or who have previously tested positive for the BRCA1 or BRCA2 gene mutations or other genetic syndromes, screening breast MRI is recommended annually in addition to mammography. Of note, gene mutation testing is not a requirement to be considered an appropriate candidate for MRI screening. If a woman tests negative for the BRCA gene mutation but has a strong family history, she may still need an MRI screening.
Additional Screening For Women With Dense Breasts Who Are Not at High Risk
Screening MRI has not been studied in average-risk women with no known cancer diagnosis. However, if a patient expresses a desire to be screening with MRI, then a full risk assessment would be helpful. Even if a patient does not have strong risk factors for breast cancer, there are a number of minor risk factors, including breast density, which together may raise her to a sufficiently high risk. The American Cancer Society states that for intermediate risk women, with a 15 to 20 percent lifetime risk (this may include women with a history of atypia on biopsy or with a personal history of breast cancer), the decision to have a screening MRI should be made on a case-by-case basis using a shared decision-making approach.
The data on screening ultrasound is limited at this point. Mammography typically finds six to eight breast cancers in every 1,000 women screened for the first time. In women with dense breasts at average risk, small studies have shown ultrasound can detect 1.6 to 4 mammographically occult cancers for every 1,000 women screened for the first time. Therefore, supplemental ultrasound adds substantially to the cancer yield in some studies. The majority of cancers found on ultrasound are smaller than 1 cm and are invasive.
However, there are two major drawbacks to the currently available data. The first is that no studies have been performed with control groups and long-term follow-up. Thus, we do not know what the clinical impact of finding these additional small cancers is – specifically whether the cancers would otherwise be detected at the next mammography screening while still small, node-negative, and at early stage, and whether there is any impact on mortality. The second drawback is that many more biopsies are generated by screening ultrasound than screening mammography, and most of these additional biopsy recommendations ultimately end up being false positives. The positive biopsy rate for lesions detected on screening mammography is 25 to 40 percent, while the positive biopsy rate for lesions found on screening ultrasound is 5 to 10 percent. This means that 90 to 95 percent of biopsies initiated by the screening ultrasound in women with negative mammograms end up showing no cancer.
Due to these concerns, there is no formal recommendation from the radiology community at this point regarding screening ultrasound. Some radiologists are opposed to it, while some believe that it has a role. The results of screening breast ultrasound may be more favorable in centers with a dedicated program. Whichever supplemental screening test is being considered, it is important to keep in mind that for patients who are not at high risk, the a priori probability of breast cancer is low. Therefore, the benefit of additional screening is diminished, whereas the potential harms remain the same.
Tomosynthesis uses similar technology to conventional mammography and is available at a number of UH sites. Recent data suggest that in general, tomosynthesis reduces false positive findings and increases detection of additional cancers in the screening populations (similar to ultrasound but not as much as MRI). Studies have demonstrated a 29 percent increase in overall cancer detection with a 41 percent increase in invasive cancer detection. Tomosynthesis also has 15 percent fewer false positives than mammograms. The biopsies initiated by tomosynthesis are more likely to result in a cancer diagnosis, translating to fewer unnecessary biopsies. Some women in Ohio who have tomosynthesis will receive patient letters stating that they have dense breasts. For these women, the primary physician may decide to inform them that they have already had a test as effective as some types of supplemental screening. Data has shown an increased cancer detection in women with all breast densities (90 percent of the population) except for fatty breasts (10 percent of the population).
The radiation dose of the combined digital mammography plus tomosynthesis examination is approximately double that of standard digital mammography alone, but this dose is still within FDA limits. Dose reduction strategies are being actively developed, in particular the use of synthesized digital mammographic images created from tomosynthesis data has received FDA approval, which would result in substantial dose reduction if the digital mammography examination could be omitted. Thus, the dose-related risk implications for women are considered acceptable.
Cost of Supplemental Screening
The Ohio legislature did not mandate insurance coverage for any supplemental breast cancer screening tests. Currently, there are insurance billing codes and CMS reimbursement for screening breast ultrasound and tomosynthesis. Patients should check with their individual insurance to confirm reimbursement rates. Screening breast MRI is usually covered for high-risk women, but may not be covered for women at average risk who simply have dense breasts. As such, women who desire certain types of supplemental screening may be asked to pay out of pocket.
From a societal perspective, supplemental screening of the approximately 50 percent of Ohio women with dense breasts would result in very substantial additional cost to the health care system. This has to be compared to the potential added benefits of finding cancers at earlier stages.