As a screening device for breast cancer, mammography is the single most effective method, asserts the American Cancer Society. Yet, despite its more than 90 percent level of accuracy in labeling a woman cancer-free, a mammogram still may miss 10 to 15 percent of malignancies, mostly in younger women who often have very dense breast tissue. “As you get older, the density of the breast on the mammogram decreases, and it’s easier to see tumors,” explains Hopkins radiologist David Bluemke, M.D.
To help make sure those harder-to-diagnose patients don’t fall through the cracks, a three-year, 15-site National Institutes of Health study taking place at Johns Hopkins is using the three-dimensional imaging modality of MRI to detect what mammography may miss. With MRI, radiologists can virtually cut through tissue and look inside lesions at any angle to determine their location and characteristics. “You’re seeing many features you wouldn’t see on mammogram,” Bluemke explains, “blood vessels, the three-dimensional shape of the tumor and, quite clearly, where it’s located in the breast. It may mean the difference in early detection of lesions before metastatic spread to lymph nodes.” MRI also works well for evaluating suspicious lesions picked up on a mammogram. Bluemke cites the case of a 42-year-old woman who felt a lump in her right breast. A mammogram identified dense breast tissue and enlarged mammary ducts but no masses. With an MRI, however, radiologists located a 1.2-cm mass within the dense breast tissue. Its pattern suggested a malignancy, which a biopsy confirmed. MRI’s other benefit, according to Bluemke, is its ability to determine the extent of an abnormality and thus help in making decisions about treatment—the extent of surgery, for instance, or how the case should be managed. Preliminary data suggest that in about one-third of patients studied so far, MRI depicted more extensive disease than a mammogram. In about 10 percent of these patients, what the MRI showed altered the treatment plan. Hopkins Medical News
Fall 1999 |
