New Breast Cancer Scan Cuts False Alarms
Researchers Say PEM Scan May Be More Accurate Than MRI
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
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
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
PEM Accurate in Women With Dense Breasts
The researchers also looked at PEM alone to see if was affected by breast
density or hormonal status. It wasn't, successfully detecting cancer in 77% of
women with extremely dense breasts and in 88% of women with dense breasts. As
for premenopausal women -- whose hormonal fluctuations during the menstrual
cycle can influence MRI results -- PEM proved accurate in 88% of cases.