Magnetic Resonance Imaging Mammograms: Best for Women at High Risk for Breast Cancer

MRI—magnetic resonance imaging—is better than mammograms at detecting breast cancers in high-risk women and could be used to help screen those who carry a genetic predisposition to the disease. Breast cancer doctors caution that the tests are too sensitive to use on women at average risk for the disease, due to the large of number of false positives. They are also four to five times as expensive and require special expertise to interpret correctly.

While only a small percentage of women carry known genetic mutations that put them at high risk for getting breast cancer, for those that do, the chance of developing breast cancer in their lifetime is as high as 80 to 90%, compared with about 12% for the average woman.

In the largest of the studies reported at the 2003 ASCO meeting, Dutch scientists recruited approximately 1900 women who had lifetime cancer risks of 15% or greater and found that MRIs were twice as sensitive as mammograms at detecting tumors. The greatest advantage was seen among women whose risk was greater than 50%. In a smaller study from Germany, researchers performed mammograms, breast ultrasound and MRIs on 461 women who either had a genetic mutation or strong family history of the disease. The results indicated that MRIs detected 95% of the cancers against 34% for mammograms and 42% for ultrasounds. In contrast to the other study, MRI was no more likely to produce false positives than mammograms were. The results for MRIs may be in part the result of the researchers’ expertise in reading the images. With the average expertise available at most centers presently, MRI should not be used for screening in the general population. Mammograms themselves have become controversial, with conflicting evidence about whether getting the regular breasts x-rays really reduces cancer deaths.