EOH: Molecular Breast Imaging Shows Potential as MRI Alternative
BALTIMORE, June 26 (MedPage Today) -- Molecular breast imaging may be a more cost-effective follow-up approach to mammography than MRI for high-risk women and those with dense tissue, according to a small retrospective study.
The two imaging techniques had a sensitivity exceeding 90% and specificity of about 50%, Carrie B. Hruska, Ph.D., of the Mayo Clinic in Rochester, Minn., reported at the Era of Hope meeting here, sponsored by the Department of Defense Breast Cancer Research Program.
Although mammography remains a reliable screening and diagnostic test for breast cancer, the imaging technique has reduced sensitivity in some high-risk women and those with dense breast tissue. Increasingly, breast MRI is being used in women who are not well served by mammography, said Dr. Hruska.
However, the high cost of MRI and need for a high level of interpretative expertise prohibit routine use for breast evaluation.
Molecular breast imaging, a nuclear medicine technique, employs specialized gamma cameras to detect the preferential uptake of the radiotracer technetium-99 sestamibi in breast disease, said Dr. Hruska.
The imaging technique's accuracy is unaffected by breast-tissue density and costs a quarter to a sixth of a bilateral breast MRI. Moreover, interpretation of molecular breast imaging exams is considerably less complex compared with MRI.
Given the potential advantages of molecular breast imaging, Dr. Hruska and colleagues retrospectively reviewed records of 48 women who had both breast MRI and molecular breast imaging within a 30-day period. Six patients had screening MRI because of increased risk for breast cancer and the remaining 42 had MRI to evaluate areas of concern left unresolved by mammography or to determine disease extent.
Imaging accuracy was determined by biopsy results or by follow-up status at 15 months for women who did not undergo biopsies.
Subsequently, 54 malignancies were diagnosed in 32 patients, 15 of them with multifocal or multicentric disease. MRI detected 53 of 54 lesions in 31 patients for a sensitivity of 98% compared with 94% for molecular breast imaging, which detected 51 of 54 cancers in 30 patients.
MRI led to correct characterization of nine of 16 true-negative results specificity, and molecular breast imaging ruled out cancer in eight of the 16 cases. False-positive results with MRI led to further evaluation of 12 patients with MRI and to nine biopsies of benign lesions. False-positives with molecular breast imaging prompted evaluation of 11 patients and seven biopsies of benign lesions.
MRI and molecular breast imaging interpretations were concordant for the presence of disease and number of cancer foci in 47 of 48 patients. The single case of discordance occurred in a patient whose MRI exam identified two cancer foci that were missed by molecular breast imaging.
Dr. Hruska reported no disclosures.
Primary source: Department of Defense Era of Hope Meeting Source reference: Hruska CB, et al "Comparison of molecular breast imaging and breast MRI for diagnostic and screening applications" Department of Defense Breast Cancer Research Program: Era of Hope 2008.
What breastcancer.org says about this article…
EOH: Molecular Breast Imaging Shows Potential as MRI Alternative
An MRI (magnetic resonance imaging) scan of the breast is a good screening method for:
- women with a high risk of breast cancer
- women with dense breast tissue (less fat than average)
- evaluating a suspicious mammogram result
Unfortunately, interpreting MRI images is more complex than interpreting mammogram images. MRI results are best read by a doctor very experienced in breast MRI interpretation. Breast MRI is also expensive. So doctors have been looking for other breast imaging techniques that are as reliable and more affordable than MRI.
The small study reviewed here found that molecular breast imaging was similar to breast MRI in detecting breast cancer. Molecular breast imaging costs much less than breast MRI and is easier to interpret than breast MRI.
In molecular breast imaging (also known as a Miraluma test, sestamibi, or scintimammography), a small amount of the molecule sestamibi that has been tagged with a radioactive substance (technetium 99) is injected intravenously. Breast cancer cells tend to take up the tagged sestamibi molecule much more than normal cells. A nuclear medicine scanner then scans the breast and looks for any areas where the radioactive substance is concentrated, suggesting breast cancer.
This study looked at the records of 48 women who had BOTH breast MRI and molecular breast imaging within 30 days:
- 42 women had the tests to evaluate an area of concern after a mammogram or to determine how much an already-diagnosed breast cancer had spread
- 6 women were at high risk of breast cancer and had the tests to screen for breast cancer
The researchers looked at the biopsy results of women who had a biopsy or looked at the medical records of women who didn't have a biopsy to see whether breast cancer was diagnosed over the next 15 months.
The records showed that 32 of the 48 women were diagnosed with breast cancer. MRI and molecular breast imaging were both good at finding breast cancers. MRI found breast cancer 98% of the time. Molecular breast imaging found breast cancer 94% of the time. Molecular breast imaging missed two breast cancers in one woman, while MRI did find these cancers.Both molecular breast imaging and breast MRI have rather high false positive rates. A false positive is an area identified as cancer that turns out to be normal. In this study, about 25% of both the MRI and molecular breast imaging findings were false positives. Besides the fear of being diagnosed with breast cancer, a false positive also means more tests (including biopsies) and follow-up doctor visits. The process can be very stressful and upsetting.
Molecular breast imaging has been used for some time now. Some doctors feel molecular breast imaging isn't good for detecting small, early breast cancers. While the results reviewed here suggest that molecular breast imaging may be a reliable and less expensive alternative to breast MRI, this study is very small and more research is needed.
Visit the Breastcancer.org Screening and Testing section to learn more about the tests used to diagnose breast cancer.
