Magnetic resonance imaging (MRI) seems to be much more sensitive than mammography for diagnosing ductal carcinoma in situ (DCIS) in general, and aggressive high-grade DCIS in particular, according to a large prospective study.

Compared with mammography, "MRI doubled sensitivity for which we were able to diagnose DCIS overall and it doubled the sensitivity specifically for diagnosing high-grade DCIS," reported Dr. Christiane K. Kuhl, at the annual meeting of the American Society of Clinical Oncology.

"High-grade DCIS is important to diagnose because it is easily curable with resection," noted Dr. Kuhl, vice chairman and professor of radiology at the University of Bonn, Germany. "If left untreated, it will progress to high-grade invasive cancer."

Dr. Kuhl and colleagues investigated the sensitivities of high-resolution MRI and state-of-the-art mammography for diagnosing DCIS. Among more than 5,000 women in the study, 167 were finally diagnosed with DCIS.

MRI was positive in 153 of 167 of these women (92%) while mammography was positive in only 93 of 167 (56%). "This difference is statistically significant at a very high level," Dr. Kuhl said.

MRI identified 98% of high-grade DCIS whereas mammography identified only 52% of high-grade DCIS. MRI identified 85% of non-high-grade DCIS and mammography spotted 61% of non-high grade DCIS.

"Mammography was less sensitive for high-grade versus non-high-grade DCIS," Dr. Kuhl pointed out.

Of the 72 DCIS that were only detected by MRI, 69% were high grade and 31% were non-high-grade. Of the 12 DCIS only detected by mammography, 17% were high-grade and 83% were non-high-grade.

Commenting on these results, Dr. Julie Gralow, of the University of Washington and moderator of the press briefing on the study said: "There is a lot of controversy over treatment of low-grade DCIS in this country...so this study showing that the highest-grade DCIS is what is most commonly found on MRI and actually missed in a good number of mammograms is really key, and I think will help us pick out which cancers really need some intervention and which might not."

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