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Magnetic resonance imaging is more sensitive than mammography in diagnosing ductal carcinoma in situ, particularly in women with high-grade breast lesions, according to a presentation by Dr. Christiane K. Kuhl of the University of Bonn, Germany.
"MRI doubled the sensitivity with which we were able to diagnose DCIS overall, and it doubled the sensitivity specifically for diagnosing high-grade DCIS," Dr. Kuhl said at a press briefing. She is lead author of an ongoing prospective study of 5,960 women at a center in Germany.
The trial participants had been referred to the center for either a screening or a diagnostic mammogram. They all underwent bilateral mammography with at least two views, spot compression where needed, and high-resolution bilateral MRI. Of the participants, 56% were referred for MRI to follow up on a previously abnormal mammogram. The median age was 55 years.
The results revealed that 167 participants were diagnosed with DCIS confirmed by biopsy. Of these, 44 cases were low grade, 34 intermediate grade, and 89 high grade. The researchers determined that 93 women (56%) were diagnosed with DCIS by mammography and 153 women (92%) were diagnosed with DCIS by MRI. This difference was highly statistically significant.
Mammography was much less sensitive for diagnosing high-grade DCIS, identifying only 52% of high-grade tumors, whereas MRI diagnosed 98%. MRI was also better at identifying non-high-grade DCIS, diagnosing 85% vs. 61% found by mammography. "Early diagnosis of high-grade DCIS helps avoid aggressive invasive breast cancer," noted Dr. Kuhl.
Mammography alone detected 12 DCIS that were not visible by MRI, but 83% of these were not high grade. MRI alone detected 72 DCIS, and 69% of these were high grade, she reported. There were 108 false-positive diagnoses with mammography and 119 false-positive diagnoses with MRI during the 5-year study period, she added.
The current study adds to calls for increased use of breast MRI, which costs more than mammography and requires specially trained radiologists. "We will struggle with the costs, and the training, and the expertise," stated Dr. Julie Gralow of the University of Washington, Seattle, who moderated the press briefing.
Discussant Dr. Claudine Isaacs of Georgetown University, Washington, said, "It is very important to note that this was a study carried out at a single tertiary care institution that obviously has huge expertise in the conduct and the interpretation of breast MRIs, and this is not extrapolatable to other institutions that do not have as much experience with this technology." She added that not all hospitals have access to these resources, which could limit the widespread utility of breast MRI.
Kuhl C.K. et al. Magnetic resonance imaging versus mammography for diagnosing ductal carcinoma in situ. Abstract 1504.
Commentary |
MRI is now an accepted screening tool for early detection of cancers in high-risk women. Although this study clearly demonstrates the potential usefulness of MRI in the diagnosis of DCIS, particularly higher risk lesions, very few women were found to have DCIS on MRI alone—41 out of 167 diagnoses—and this out of a population of almost 6,000 women. MRI is costly. It requires specialized equipment and expertise—and it often necessitates biopsies and follow-up scans. DCIS, although common, is associated with less than 2% mortality at 10 years, so the impact of MRI screening would be impossible to assess in the general population. The issue is not as much political as it is about appropriate use of technology. MRI should be considered for women at very high risk for DCIS and invasive cancer. These data further support that approach. — Hope S. Rugo, M.D.
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