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    New Breast Cancer Scan Cuts False Alarms

    Researchers Say PEM Scan May Be More Accurate Than MRI
    WebMD Health News
    Reviewed by Louise Chang, MD

    Dec. 2, 2008 (Chicago) -- A new type of scan may cut down on the number of false alarms associated with currently used techniques for spotting breast cancer, researchers report.

    The method, called positron emission mammography, or PEM, is also at least as accurate, if not more accurate, than breast MRI at finding true cancers, says Kathy Schilling, MD, director of breast imaging and intervention at the Center for Breast Care at Boca Raton Community Hospital in Florida.

    Women undergo breast MRI when standard mammography results are hard to read, typically due to very dense breast tissue. But breast MRI is also associated with a high rate of false-positive test results that indicate cancer is present when it is not. Researchers believe that's due in part to hormonal changes that occur during a woman's menstrual cycle.

    PEM is not affected by either breast density or a woman's hormonal status, Schilling tells WebMD.

    That means "fewer women will be called back for additional tests and biopsies, which is emotionally traumatic for the patient as well as the family," she says.

    Schilling presented results of a new study of PEM at the annual meeting of the Radiological Society of North America (RSNA).

    Breast-Specific PET Scan

    PEM can be thought of as breast-specific positron emission tomography, or PET, says RSNA spokeswoman Stamatia Destounis, MD, of Elizabeth Wende Breast Care in Rochester, N.Y.

    It involves injecting the body with a small amount of radioactive tracer dye that is bound to sugar. Fast-growing cancer cells feed on the sugar and utilize it more quickly than normal cells, so they appear brighter on images created by the PET scanner.

    PEM isn't meant to replace mammograms or breast MRI, but rather act as an extra tool, Destounis tells WebMD. "It may fulfill a need when mammograms and MRI don't give us all the information we need."

    In the new study, 182 women with breast cancer underwent PEM and breast MRIs. Both techniques proved 89% accurate at spotting breast cancer.

    But PEM correctly detected 90% of early, noninvasive cancers known as ductal carcinoma in situ (DCIS) confined to the ducts of the breast, while MRI was only accurate in 83% of cases. And PEM spotted 100% of early, tiny, invasive tumors less than 5 millimeters in diameter, while MRI found them only 75% of time.

    PEM gave false-positive results to 18% of women who didn't have tumors. The comparable figure for MRI testing was 33%.

    All the findings could have been due to chance. But Schilling thinks that they will take on what researchers call statistical significance -- meaning there's less than five-in-100 odds that they're due to chance -- as more women are studied.

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