Saturday, November 14, 2009

Are MRIs Better at Screening for Women at High Risk of Breast Cancer?

Mammograms are the test of choice for most breast cancer screening, and studies have shown that they save lives.  But for high-risk women—those with dense tissue, a family history of breast cancer, the BRCA1 or BRCA2 gene, or previous breast cancer—the MRI might be a better choice.

The difference between the two:

Mammography is based on a single two-dimensional projection of the breast.  MRIs offer a three-dimensional image.  And while, on the face of it, MRIs sound automatically superior, they also can offer the risk of false positives—suggesting cancer where there is none.  That is why mammograms are still recommended for women at low or moderate risk.  

Several studies have looked at the difference between the two for high-risk women:

Research published  in the American Journal of Roentgenology (April, 2009)  demonstrated that a specific type of MRI—the newest generation 3T MRI—offered early diagnosis of breast cancer for women in hish risk categories.  Researchers at the University of Toledo studied 434 high risk women between May 2006 and May 2007.  The 3T MRI detected all of the 66 malignant tumors—a 100 percent rate of effectiveness—while mammograms were 86.4 percent accurate and sonogams 81.8 percent accurate.   This rate of accuracy was superior to the older generation of MRIs—the 1T and 1.5T models.  In their conclusions, researchers recommended MRIs only for high-risk women, however, as mammography is effective, and far less expensive, for women at normal or low risk. 

Research in the journal European Radiology (May, 2008) determined that MRIs may detect tumors associated with the BRCA gene better than mammography.  These tumors often look like benign lesions, with a rounded shape or sharp margins, and MRIs may be better at differentiating between benign and malignant tumors. 

Researchers in England studied the effectiveness of MRIs versus mammograms as part of the ongoing MARIBS (magnetic resonance imaging in breast cancer study). The research, published in Breast Cancer Research (November, 2009)  included 837 women with no symptoms, but with the BRCA1 or BRCA2 gene or first-degree relatives with breast or ovarian cancer.  Fifty-six of the women ultimately developed breast cancer.  Of those, 19 were diagnosed during the study and 37 were diagnosed later. They found that MRIs were more effective in identifying cancer in women carrying the BRCA1 mutation and, overall, provided a clearer definition of potentially cancerous tissues.  They stopped short of recommending MRIs for general screening, though, because the number of women with cancer in their study was so small that their findings could be due to chance.

Based on these and other studies, the American Cancer Society has revised it screening guidelines and now recommends MRIs in addition to yearly mammograms for women who meet at least one of the following conditions:        

•they have a BRCA1 or BRCA2 mutation

•they have a first-degree relative (parent, sibling, child) with a BRCA1 or BRCA2 mutation, even if they have yet to be tested themselves

•their lifetime risk of breast cancer has been scored at 20%-25% or greater, based on one of several accepted risk assessment tools that look at family history and other factors

•they had radiation to the chest between the ages of 10 and 30

they have Li-Fraumeni syndrome Li-Fraumeni syndrome, Cowden syndrome,  or Bannayan-Riley-Ruvalcaba syndrome, Bannayan-Riley-Ruvalcaba syndrome or may have one of these syndromes based on a history in a first-degree relative.



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