At present, the gold standard of care for women at high risk for breast cancer is annual mammography and a magnetic resonance imaging (MRI) scan, usually done at the same visit or at different appointments scheduled fairly close together. This may change, as a new pilot study provides evidence that alternating these tests every six months may be the best way to detect breast cancer at its earliest, most treatable stages.
Researchers at the University of Texas MD Anderson Cancer Center conducted a retrospective study in which they reviewed the medical records of 334 women who had participated in its high-risk breast-cancer screening between January and December 1997 — 86 of whom had undergone the alternate screening every six months. The program alternating MRI and mammography screening detected nine cancers among the 86 women.
According to lead author Huong Carisa Le-Petross, MD, associate professor, department of diagnostic radiology at University of Texas, MD Anderson Cancer Center, “MRI found eight of the nine cancers. In those cases all of the mammograms that were done six months earlier were negative. No cancer was detected by mammography alone.” The undetected cancer, a small tumor (one millimeter), was missed by both screening techniques and was found during a mastectomy. The researchers presented their findings at the 31st Annual San Antonio Breast Cancer Symposium in December 2008.
But if MRI is superior to mammography, why undergo mammography at all? For one thing, MRI is expensive and typically only covered by insurance if a woman is high-risk. Also, explained Dr. Le-Petross, each modality has different strengths. “MRI is more sensitive than mammography for detecting some types of cancers, but mammography is superior to MRI for picking up calcifications.” Calcifications, especially micro-calcifications that are clustered together, may indicate cancer that is contained inside the ducts, or they could be precancerous lesions.
Hence, undergoing both screening tests increases a woman’s chances of finding early-stage breast cancer, when it is most easily treatable. In 2007, the American Cancer Society established new guidelines for women at high risk for breast cancer, recommending that they undergo both an annual MRI and mammogram, plus a clinical breast exam beginning at age 30. You can alternate these, having one each six-month period. Women are considered at high risk for breast cancer if they have one or more of the following:
One thing to consider is that while MRI scans are more sensitive than mammograms, they also are more likely to show spots in the breast that may or may not be cancer, leading to false-positive results and unnecessary biopsies, said Dr. Le-Petross.
