October: Is MRI better than mammogram for detecting breast cancer?

Is MRI better than mammogram for detecting breast cancer?

Lancet recently reported (vol 370, August 11, 2007) a study comparing MRI (magnetic resonance imaging) and mammography in their ability to detect ductal carcinoma in situ (DCSI). DCSI is generally accepted as a direct precursor to breast cancer. More specifically a high, not low, grade DCIS usually progresses to invasive breast cancer. Early detection of a high grade DCSI is critical in preventing transformation of DCSI into invasive breast cancer since DCSI can be treated with local excision. Currently, mammography is most widely used for breast imaging, and MRI is only used as an adjunct to mammography. MRI is used if more detailed examination is warranted based on the results of mammography.

The study included 7,319 women and was followed for 5 years (prospective study) at the breast center at the University of Bonn Hospital and Medical School in Germany. All women underwent both mammogram and MRI, and both were completed and interpreted before any biopsy procedures were done to avoid all biases. The results suggest that MRIs performed better in diagnosing DCSI (both high and low grades). For example, 167 DCSI was definitively diagnosed through biopsies but only 56% or 93 of 167 cases were picked up by mammograms alone. On the other hand, MRI accurately diagnosed DCSI 92% or 153 cases. MRI performed even better in detecting high grade DCIS: 98% versus 52% detected by mammograms.

Should MRI’s be recommended instead of mammograms as a general screening diagnostic for breast cancer? Despite the fact that this was a 5 year study including a large number of women, these results are from one breast center using highly trained radiologists to interpret the results. Unless the radiologists are highly experienced and trained to read both the mammogram and MRI, these results might not be replicable in other centers. In addition, standards used in the EU countries are different than those used in the United States. Therefore, to use MRI for the general population as a routine breast cancer screening method might be too premature. However, MRI might be recommended for women with a strong family history of breast cancer.

Kuhl, C., Bieling, H., Wardelmann, E., Leutner, C., Konening, R., and Kuhn, W. (2007) “MRI for diagnosis of pure ductal carcinoma in situ: a prospective observational study,” Lancet, vol 370, August 11, 485-492.