April 8, 2012 by Robert Wascher
Filed under A Cancer Prevention Guide for the Human Race, Breast Cancer, Breast-Specific Gamma Imaging, Cancer, Cancer Prevention, False-Positive, MRI, Magnetic Resonance Imaging, Mammograms, Mammography, PEM, Positron Emission Mammography, Sensitivity, Ultrasound, Weekly Health Update, breast cancer prevention, breast cancer risk, cancer detection, cancer risk, cancer screening
New research shows that adding MRI to mammogram and ultrasound increases breast cancer detection rate, but with a high rate of false positive results.
ADDITION OF MRI TO MAMMOGRAM AND ULTRASOUND INCREASES BREAST CANCER DETECTION
Currently, women who are at an average risk of developing breast cancer are advised to undergo annual screening mammograms beginning at 40 to 45 years of age. Mammography, like any medical test, is not perfect (at least 10 to 20 percent of breast cancers will not show up on a mammogram among women who are at average risk for this type of cancer). Moreover, mammography, which relies upon low-powered x-rays to form images of the breasts, is especially challenged by women with dense breast tissue, which is, by itself, a known risk factor for breast cancer.
In many cases, the addition of ultrasound to mammography can help to form more accurate images of dense breast tissue, and is also useful for further evaluation of indeterminate breast abnormalities identified by mammography. (Also, both the lobular sub-type of breast cancer and small “low-grade” breast cancers tend to show up better on ultrasound than they do on mammograms.) Together, the combination of mammography and ultrasound can accurately detect approximately 85 to 90 percent of breast cancers in women with normal-density breast tissue; but, once again, in women with dense breast tissue (including most women under the age of 40), the sensitivity and overall accuracy of mammography plus ultrasound is often considerably decreased.
Magnetic resonance imaging, or MRI, has become a popular tool for breast imaging, although, like mammography and ultrasound, MRI of the breast has its downsides as well. MRI is known to be much more sensitive than either mammography or ultrasound in identifying breast cancers, with most studies showing a 95 percent or greater sensitivity associated with MRI. However, this exquisite sensitivity of breast MRI, as I discuss in my bestselling book, A Cancer Prevention Guide for the Human Race, is also associated with poor specificity (i.e., a high false-positive rate). Because of its poor specificity, MRI scans of the breast will be wrong, or falsely-positive, in 15 to 35 percent of cases where an abnormality is detected. Although there are other reasons as well, this high false-positive rate is the primary reason that MRI scans are not routinely used to screen for breast cancer.
As I have noted, none of these three common breast cancer screening tests are perfect, and each of them will miss some cancers that the other types of scans might pick up. With this information in mind, a newly published study, which appears in the current issue of the Journal of the American Medical Association, examines the potential role of ultrasound and MRI scans as supplements to screening mammograms in women who are at an increased risk for developing breast cancer.
In this prospective clinical research study, 612 women deemed to be at increased risk for breast cancer underwent three years of annual breast cancer screening exams with mammography and ultrasound. After completing these three years of annual screening with mammography and ultrasound, these women additionally underwent MRI scans of their breasts. Abnormalities suspicious for cancer, based upon any of these three diagnostic tests, were further evaluated by biopsy. This cohort of women volunteers was then followed for an additional 12 months, to monitor them for any signs of interval development of breast cancer.
The 612 women who underwent mammography, ultrasound and MRI screening were also part of a larger group of 2,662 high-risk women (54 percent of whom had a personal history of a prior breast cancer) who enrolled in this study, and who underwent annual breast cancer screening with both mammography and ultrasound. Altogether, 110 of these 2,662 women were diagnosed with a new breast cancer during the course of this prospective clinical research study.
The results of this study clearly illustrate the limitations of currently available breast cancer screening tests, particularly among high-risk women. Following three years of annual screening, only 52 percent of the breast cancers that arose were detected by mammography alone in these high-risk women, although the false-positive rate of mammography was very low, at 9 percent. The addition of ultrasound to mammography improved the sensitivity, or detection rate, to 76 percent, with a false-positive rate of 16 percent. When MRI was added to mammography and ultrasound, the detection rate (sensitivity) for breast cancer improved, significantly, to 100 percent, although the false-positive rate increased greatly due to the poor specificity of MRI and, to a lesser extent, ultrasound. When these three breast imaging modalities were combined, 35 percent of the abnormalities identified turned out to be benign lesions, and not cancer, following biopsy or other confirmatory diagnostic procedures.
This study confirms that essentially 100 percent of detectable breast cancers can be identified using a combination of mammography, ultrasound and MRI. However, this high level of sensitivity comes at a significant cost in that more than one-third of the abnormalities identified by the combined use of these three breast imaging modalities will, upon further testing, including biopsy, turn out to be completely benign. Therefore, this high false-positive rate, particularly associated with breast MRI, is the Achilles heel of this combined imaging approach to breast cancer screening.
Fortunately, there are emerging new breast imaging technologies that appear to have the same very high sensitivity rate as MRI, while maintaining the high specificity (i.e., low false-positive) rate of mammography. Among these promising technologies are Breast-Specific Gamma Imaging and Positron Emission (PET) Mammography (also known as “PEM”). Ultimately, these newer technologies, as well as even newer technologies, will most likely someday replace the use MRI to screen for breast cancer.
For a groundbreaking overview of cancer risks, and evidence-based strategies to reduce your risk of developing cancer, order your copy of my bestselling book, “A Cancer Prevention Guide for the Human Race,” from Amazon, Barnes & Noble, Books-A-Million, Vroman’s Bookstore, and other fine bookstores!
Within one week of publication, A Cancer Prevention Guide for the Human Race was ranked #6 among all cancer-related books on the Amazon.com “Top 100 Bestseller’s List” for Kindle e-books. Within three months of publication, A Cancer Prevention Guide for the Human Race was the #1 book on the Amazon.com “Top 100 New Book Releases in Cancer” list.
Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity
Dr. Wascher is an oncologic surgeon, professor of surgery, cancer researcher, oncology consultant, and a widely published author
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