What is the Best Breast Cancer Screening Tool?
A Q& A with Dr. Valerie Fein-Zachary, a radiologist specializing in Breast Imaging and Co-Director of the Breast Imaging Fellowship at Beth Israel Deaconess Medical Center.
Q: What are the current technologies available for breast cancer screening?
Dr. Fein-Zachary: The best breast cancer screening test for women with low or average risk for breast cancer is mammography. It's readily available and does not require special preparation other than washing off deodorants prior to the exam. For women who are at a higher risk for developing breast cancer (for example, women who have a greater than 25 percent lifetime risk or who have BRCA genes), Breast MRI is recommended for screening, in addition to mammography.
Q: Who should receive a mammogram and how often?
Dr. Fein-Zachary: The recommendation of the American Cancer Society (ACS) and the American College of Radiology (ACR) is that women should have an annual mammogram starting at age 40. If you have a family history of breast cancer, it is recommended that you start your screening studies 10 years prior to the age of diagnosis of the earliest breast cancer in your family. For example, if your mother had breast cancer at age 42, you should begin annual screenings at age 32. If a woman under age 30 needs early screening, she should consider Breast MRI in order to limit radiation exposure.
Q: What was the recent screening controversy about?
Dr. Fein-Zachary: In the fall of 2009, there was a huge political uproar over the new guidelines of the U.S. Preventative Services Task Force (USPSTF). They said that women in their 40s should consult with their doctors as to whether or not they needed screening mammograms. They concluded that women aged 50 to 74 should have mammograms every two years instead of yearly and that there was insufficient evidence to recommend screening women age 75 or older. Furthermore, they discouraged teaching women to do breast self-examinations, and also felt that there was insufficient evidence for women to have annual physicians' clinical breast examinations.
Read more about the recommendations »
Summary of Recommendations
- The USPSTF recommends biennial screening mammography for women aged 50 to 74 years.
- The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take patient context into account, including the patient's values regarding specific benefits and harms.
- The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of screening mammography in women 75 years or older.
- The USPSTF recommends against teaching breast self-examination (BSE).
- The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of clinical breast examination (CBE) beyond screening mammography in women 40 years or older.
- The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of either digital mammography or magnetic resonance imaging (MRI) instead of film mammography as screening modalities for breast cancer.
Many criticisms were leveled against the USPSTF by medical groups and women's advocacy groups, including their use of mortality as an end-point for women's health, insufficient data regarding women's acceptance of recalls and biopsies for abnormal mammogram findings that were not cancer, and so-called "overtreatment" of early breast cancer (minimally invasive carcinoma and ductal carcinoma in situ - DCIS). There was also concern that insurance companies would stop covering annual screening mammograms; however, most insurers have not changed their policies.
Many doctors continue to recommend annual mammograms for their patients. In today's mobile society, when women may change providers every few years, I often encourage patients to periodically continue their self-breast examinations, so that they are more aware of what's "normal" for them, and to actively participate in their own breast health.
Q: What happens during a mammogram?
Dr. Fein-Zachary: A mammogram takes 15 to 20 minutes and begins with you removing your blouse or shirt and bra (if you wear one) and putting on a hospital gown. The mammogram technologist positions your breast between the compression paddle and the detector plate underneath, and she compresses your breast. The compression is extremely important because it allows us to separate breast tissue so we can see through it better. The breast has to be compressed a certain minimum amount in order for the machine to take the exposure. Typically, two views are taken of each breast.
Read more: Frequently Asked Questions about Mammograms »
Q: Do breast implants inhibit a mammogram?
Dr. Fein Zachary: Implants inhibit our ability to see the underlying breast tissue which is why we need to take extra views. If a woman has breast implants, the technologist will push the implants out of the way and take additional images of each breast. If a woman with implants feels a lump in her breast, we will do an ultrasound in addition to the mammogram because often ultrasound allows us to see a lump that may be obscured by the implant.
Q: How does film-screen mammography differ from digital mammography?
Dr. Fein-Zachary: Digital mammography utilizes the latest technology available for breast imaging. Similar to a digital camera, images are collected digitally so they can be manipulated by software programs which enhance image characteristics. If we see something of concern on a digital mammogram, we can digitally magnify that area on our computer monitor.
With older film mammography, a single piece of film is put into each cassette and the technologist has only one chance to obtain the correct exposure for an optimal image. Once the film is exposed, it can't be manipulated.
Most mammography centers are moving to digital mammography. Beth Israel Deaconess Medical Center, BID-Needham, BIDHC-Lexington, BIDHC-Chelsea, and our outpatient offices at 1101 Beacon Street and 25 Boylston Street are completely digital. This offers our patients the advantage of being able to have their mammograms anywhere in our system because images can be transferred electronically. Our newest facility, BID-Milton, however, has not yet converted to digital mammography.
Q: Who should get a digital mammogram?
Dr. Fein-Zachary: A large national study that analyzed the differences between film and digital mammography, called DMIST (Digital Mammography Imaging Screen Trial), followed 49,528 asymptomatic (no breast lumps) women at 33 sites in the U.S. and Canada. They found that digital was more accurate in women under the age of 50, women who had extremely dense breast tissue and women around the age of menopause.
Q: What are the advantages of digital mammography?
Dr. Fein-Zachary: With digital mammography, there is a slight decrease in radiation dosage, a faster exposure time (imperceptible to us) and improved image contrast. Digital mammograms can also be transmitted electronically from one facility to another, allowing for better coordination among a patient's physicians.
Q: When is breast ultrasound used?
Dr. Fein-Zachary: Breast ultrasound is a used for problem solving, for example, when a woman finds a lump or a mammogram detects a possible cyst or a suspicious mass. Ultrasound helps distinguish solid lesions from cysts, and it can often help us differentiate between benign and malignant (cancerous) solid lesions. If a lesion is felt to be probably benign on ultrasound, we can make a recommendation for a six- month follow-up ultrasound study rather than a biopsy.
Read more: Frequently Asked Questions about Breast Ultrasound »
Q: What is the role of MRI in detecting breast cancer?
Dr. Fein-Zachary: The ACS recommends that high-risk women who have the breast cancer gene (BRCA 1 or BRCA 2) or other high-risk factors should get annual screening with Breast MRI in addition to mammography. MRI does not replace annual mammograms because mammograms pick up tiny microcalcifications that the MRI can't detect.
Read more: Frequently Asked Questions about Breast MRI »
Q: How does breast MRI work?
Dr. Fein-Zachary: MRI uses the principles of magnetism to generate images of the breasts. In addition, MRI gives us dynamic information about blood flow in breast tissue because we inject contrast into the body through an IV and re-image the breast over several time points. This gives us a map of the vascular flow to breast masses, called kinetic information. The size and shape of breast masses, called morphology, along with the kinetics increases our accuracy of determining whether masses are benign or malignant.
For example, if we see an area of tissue and the contrast increases progressively over time (a type 1 curve), we know that it is most likely normal breast tissue. By contrast, cancers typically have an early peak of enhancement and then a decrease in contrast enhancement over time. This rapid wash-in and rapid wash-out of contrast (a type 3 curve) is of concern and these lesions will most likely be biopsied.
Some women are discouraged from having MRIs because of the risk of a false-positive finding. These can be due to hormonal influences on contrast enhancement as well as normal structures, such as lymph nodes, that mimic the appearance of small cancers. We recommend that patients have their MRIs at institutions with expert MRI readers and also at those institutions that perform MRI-guided breast biopsies. Beth Israel Deaconess Medical Center and BID-Needham are two such centers.
Above content provided by Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.
Posted March 2012