More Than Mammograms Needed to Diagnose Breast Cancer
Twelve states have enacted laws requiring physicians to inform women when their mammograms show they have dense breast tissue. New Jersey, my home state, is not one of them. I helped introduce a breast density inform bill in the New Jersey Senate two years ago; it is now being picked apart and diluted in the New Jersey Assembly.
Legally, radiologists are required to tell referring physicians about their patients’ density. But no one is required tell the patients. Until every state has a law, or a federal law is enacted, those of us on the front lines are trying to get the word out to women that breast density is a cancer risk.
The American College of Radiology (ACR) estimates that 47 percent of women have dense breast tissue and women with density are two to six times more likely to develop breast cancer. Not only does density increase the risk of cancer; it can interfere with the accuracy of mammograms. Breast density inform laws suggest that women with dense breasts talk to their doctors about supplemental screening – tumors are seen differently on other imaging modalities.
Briefly, breasts are composed of three kinds of tissue: fatty, glandular and fibrous. Fatty tissue is black on a mammogram. Glandular and fibrous – the dense tissue - are white. Tumors are also white so they can be hidden by the dense tissue. It’s like looking for a snowflake in a snowstorm - a perfect storm for missed cancers on a mammogram.
The percentages of each kind of tissue vary in women and are mostly based on genetics. As women get older the percentage of glandular tissue may be replaced by fatty tissue, making mammograms easier to read. However this is not always the case and any fatty replacement may not be significant.
The ACR has developed a standard way of describing mammogram findings called the Breast Imaging Reporting and Data System (BI-RADS). BI-RADS classify breast density into 4 groups. When women are classified BI-RADS 3, heterogeneously dense, or BI-RADS 4, extremely dense, mammogram accuracy plunges.
Individualized risk assessment is necessary to determine what type of screening a woman should have and how often she should be screened. I frequently tell patients that breast cancer diagnosis is a puzzle and a radiologist has to be a detective who tracks down the pieces and puts them together. Technology provides the tools; we have to use them in the right way.
Here is a review of screening procedures so you know what is available, how imaging types are different from each other, and why you may or may not need to consider them.
Mammography is still the gold standard because it has been proven time and again to save lives. Mammography is excellent at finding cancers in women with fatty tissue. Women with dense breast tissue still need mammograms because there are abnormalities that are only seen with mammograms such as microcalcifications and subtle tissue distortion.
Breast Tomosynthesis, also called 3D mammography, acquires images at multiple angles which are then reconstructed to reduce overlap in areas of dense tissue. Tomosynthesis is most useful in high volume practices where patients get a standard four view mammogram and sometimes have to be called back. While the images from Tomosynthesis can be clearer, tumors still show up white against white tissue.
Breast Ultrasound uses sound waves, without radiation, to look at the breast tissue. On Ultrasound, tissue is white but tumors are gray. Studies dating back to 1998 have demonstrated that adding Breast Ultrasound to Mammography in women with dense tissue doubles the numbers of early cancers found. When an abnormality is found with Ultrasound, Ultrasound guided biopsies are less invasive and less expensive than biopsies guided by Mammography or surgical biopsies.
Automated Whole Breast Ultrasound (AWBUS) is an exciting new technology that also uses Ultrasound waves but the transducer is automated. AWBUS accumulates 3,000-5,000 images in a cine (movie) format. Changes from image to image (gradation) can be seen that might be missed in a series of still images. AWBUS takes out the subjectivity that can be involved in hand held Ultrasound and may be able to detect smaller and earlier cancers.
Molecular Breast Imaging (MBI) is a great technology for women with dense breast tissue, high risk patients and women with breast implants. In a recent Mayo Clinic study comparing molecular imaging with mammography, MBI detected three times as many cancers in women with dense breast tissue. Molecular imaging looks at the metabolism, or activity, of the breast tissue. A patient is given an injection of a short-lived radioactive agent which accumulates in tumor cells more than it does in normal cells. Using a gamma camera, tumors show up as black spots on the resulting image. I use a system called Breast Specific Gamma Imaging (BSGI) from Dilon Diagnostics in my office.
Magnetic Resonance Imaging (MRI) shows activity due to blood flow by using a powerful magnetic field to produce detailed images of the breast tissue, following an intravenous injection of contrast. Cancers show increased areas of blood flow.
Each technology has advantages and disadvantages. With every gain in sensitivity, the ability to find an abnormality, there is a gain in false positives, a result indicating a malignancy that with further testing is found to be benign. You should be going to a radiologist who specializes in breast imaging and is familiar with your risk profile including your history, your family history and breast density.
If you have a strong family history of breast cancer, you should look into Genetic Testing. The job of our BRACA genes is to keep breast cells functioning smoothly. Genetic Testing on a blood sample determines if the genes are damaged. Women with BRACA1 or BRACA2 gene mutations have a higher risk of developing breast or ovarian cancer.
Approximately 5 – 10 percent of breast cancer cases are caused by genetic mutation. Consider genetic testing if you have blood relatives who were diagnosed with breast cancer under the age of 50; a family member with both breast and ovarian cancer; family members with cancer in both breasts; Eastern European (Ashkenazi) Jewish ancestry or a male family member with breast cancer.
If you have a strong family history of breast cancer, find out if any of those relatives have had genetic screening. If their tests were negative and so are yours, you may still be at higher risk of developing breast cancer. Genetic testing is still in its infancy. We know that other genetic abnormalities are implicated in causing cancer but we don’t yet know what they are or how to test for them.
Be your own advocate. Know your family history and have an annual mammogram at the minimum. Ask your doctor whether or not you have dense breasts and if you do, discuss supplemental screening. You need to complete the puzzle that is your breast health.