• Evaluating breast cancer imaging tools

    July 2007

    Breast cancer is the second-leading cause of cancer-related deaths among women in the United States, with more than 40,000 dying annually of the disease. The good news is, the death rates are declining—down 24 percent between 1989 and 2003. Early detection and improvements in therapy have contributed greatly to the decline in mortality.

    Several recent studies...call into question who should be screened as well as how and when. 

    The main screening techniques for breast cancer are monthly self-examination or clinical breast exams by a physician; mammograms; and magnetic resonance imaging (MRI) scans. In addition, there are the enhancements of computer-aided detection (CAD) for mammography and digital mammography.

    While the news of better survival rates is welcome, several recent studies into screening techniques for breast cancer may have created confusion among women. They call into question who should be screened as well as how and when.

    Mammography has been clearly shown to reduce breast cancer deaths among women 50 to 70 years of age. 


    The most common breast cancer screening tool is mammography. It has been clearly shown to reduce breast cancer deaths among women 50 to 70 years of age. However, there is still a debate over how beneficial mammograms are to women under 50, where only 25 percent of the cancer cases are diagnosed.  The American Cancer Society recommends yearly screening mammograms beginning at age 40. The American College of Obstetricians and Gynecologists’ guidelines are mammograms every one to two years.

    Recently, however, the American College of Physicians issued its recommendations, saying screening mammograms for women under 50 should be done on an individualized basis, after a physician assesses a woman’s breast cancer risk. At issue are the risks of false-positive results, false reassurance, procedure-associated pain and the possible treatment for lesions that would not have become cancerous.

    CAD and digital mammography

    CAD, a technique designed to improve interpretation of mammograms, can actually degrade the performance of the mammograms, according to a multi-facility study reported April 5 in The New England Journal of Medicine (NEJM). The study involved more than 429,000 mammograms and 2,351 cases of cancer that were detected at 43 facilities in the Breast Cancer Surveillance Consortium. Researchers found that this tool not only failed to increase the cancer-detection rate but also resulted in significantly more false positives and unnecessary biopsies.   

    Digital mammography, another computer-based advance, appears to improve the accuracy of examination in younger women with dense breasts, according to a 2005 study in the NEJM. Digital mammography takes an electronic image of the breast and stores it directly in a computer, allowing the recorded data to be enhanced, magnified or manipulated. Film mammography units use film to both capture and display the image.

    "Mammography...is least effective in the screening of dense breasts...which ...are a substantial risk factor for breast cancer."
    – Ferris M. Hall, MD

    MRI evaluation

    In an editorial accompanying the CAD mammography study, Ferris M. Hall, MD, a diagnostic radiologist, suggested that a combination of genetic risk profiling and MRI screenings would be a more valuable tool than mammography.

    “Mammography is an inherently poor, two-dimensional projectional method being used to diagnose small, three-dimensional cancers,” he wrote. “It is least effective in the screening of dense breasts, which, as emphasized in another recent study, are a substantial risk factor for breast cancer.”

    The American Cancer Society recently released guidelines recommending that women at high-risk of developing breast cancer undergo MRI scans along with their annual mammograms. The high-risk group includes women with at least one of the following: the BRCA1 or BRCA2 gene mutation, a first-degree relative with one of the mutations or a lifetime breast cancer risk of 20-25 percent or higher based on family history or other factors.

    In particular, women newly diagnosed with breast cancer would benefit from MRI scans of the opposite breast, according to a new national study sponsored by the National Cancer Institute and conducted by doctors of the American College of Radiology Imaging Network. The study, published in the NEJM, showed MRI scans detected more than 90 percent of cancers in the opposite breast that were missed by mammography.

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Page last updated: 8/7/2015 1:05:50 PM
  • What the news means for you

    Benefits of screening tools outweigh risks

    Angela R. Moore, MD,

    Wright, Heather, MDMammography isn’t a perfect test, but I think that’s what people expect it to be. If you look at the sensitivity of mammography in general, we know that it can miss up to 10-15 percent of breast cancers. This is usually because of the density of the breast tissue, which makes it harder to see smaller cancers, or because of the presence of invasive lobular cancer, a type of cancer that grows in sheets of cells that are more difficult to detect with a mammogram as it can mimic normal breast tissue.   

    “Both the American Cancer Society and the American College of Radiologists recommend annual mammograms for women 40 and over.” 

    When we look at a screening tool we have to assess how effective it is in picking up cancers versus the number of false positives and negatives that result from it. Routine annual mammograms for women under 50 have always been controversial because it’s difficult to determine the benefit unless a woman is in a high-risk group.

    However, data has shown that there is a moderate decrease in mortality when younger women have mammograms. And we do know that these women tend to have more aggressive breast cancers, so early detection is important. Both the American Cancer Society and the American College of Radiologists recommend annual mammograms for women 40 and over. Those are the guidelines I follow as well.

    Mammography does a good job in detecting ductal carcinoma in situ, or DCIS, an early type of breast cancer that is confined to the milk ducts and associated with micro-calcifications. There has always been a controversy within the medical community about how aggressively to treat these cancers. Some never go beyond the duct while 15-50 percent can break out of the duct and become invasive carcinomas, depending on the histologic grade of the DCIS. Picking up cancers that might not develop any further doesn’t really impact survival rates, but most women wouldn’t want to take the risk of foregoing treatment.

    Computer-aided detection and digital mammography

    CAD is designed to help radiologists read mammograms by marking suspicious spots on the image. UK has had CAD for several years, and the software has improved over time. It’s used most commonly in conjunction with digital mammography.

    “CAD is not making the decision to call a woman back for biopsy or further testing; the radiologist is.” 

    While the study in The New England Journal of Medicine reports that CAD didn’t improve detection of invasive cancers, it did show that it picked up more DCIS. I find that CAD is useful in picking up calcifications. The majority of calcifications that develop in the breast tissue are from benign causes. However, we often end up doing a biopsy when we find them because it can be difficult to tell the benign forms from those associated with cancer. Only about 20-30 percent of the biopsies we recommend will reveal the presence of cancer.

    We have to remember that CAD is not making the decision to call a woman back for biopsy or further testing; the radiologist is. Furthermore, the majority of what CAD marks on the mammogram will turn out to be nothing, and we make the decision based on comparison to prior mammograms.

    MRI evaluation

    More and more women are asking for an MRI screening, but not everyone needs one. Like other tools, it has its limits. We often use MRI when a woman has been diagnosed with breast cancer because it sometimes shows the extent of the disease better than a mammogram and may change the surgical options—for example, from a lumpectomy to a mastectomy.

    Also, in those patients recently diagnosed with a breast cancer, up to 5 percent of the time we’re seeing an abnormality in the other breast with MRI that we didn’t see on the mammogram. MRI is also useful to monitor shrinking in large tumors as the patient undergoes chemotherapy prior to surgery.

    Sometimes a woman will present with a palpable axillary lymph node in which biopsy shows metastatic breast cancer, yet we see no abnormality on her mammogram or even an ultrasound. We do an MRI in those instances.

    Many women want an MRI because they can’t tolerate a mammogram. Mammograms aren’t comfortable, but they shouldn’t be intolerable if you have a good technologist. MRIs aren’t the most comfortable test, either. You’re lying on your stomach with your breasts in a coil device that applies light compression and your hands are stretched above your head. We give you an IV to administer contrast and tell you not to move for 30 minutes.

    If a woman has a 25-percent or greater risk of breast cancer, I would recommend a breast MRI screening in addition to a yearly mammogram. If the risk is 15-24 percent, she should talk to her doctor about getting an MRI. But even in this group, women still need an annual screening mammogram. Below 15 percent risk, a breast MRI is not recommended.

    The future of breast imaging

    One of the most exciting technologies on the horizon is digital tomosynthesis, which takes a three-dimensional picture of the breast using an X-ray. It’s very exciting because it holds promise for showing a better view of the breast and eliminating the problem of overlapping tissue, one of the major reasons for calling women back for further imaging. There is also less compression and less discomfort. Right now, tomosynthesis is used only in research but it should be available within the next five years.

    Dr. Moore is director of breast imaging at the UK Comprehensive Breast Care Center and assistant professor of diagnostic radiology in the UK College of Medicine.

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