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Magnetic resonance imaging (MRI) seems to be much more sensitive than mammography in diagnosing ductal carcinoma in situ (DCIS) in general, and aggressive, high-grade DCIS in particular. Magnetic resonance imaging (MRI) seems to be much more sensitive than mammography in diagnosing ductal carcinoma in situ (DCIS) in general, and aggressive, high-grade DCIS in particular, according to the results of a large study presented at the annual meeting of the American Society of Clinical Oncology.

DCIS is a noninvasive, precancerous condition that can progress to invasive cancer if untreated. DCIS can be any one of a wide variety of pathological tissues that are classified into subtypes based largely on their appearance. Some subtypes appear to be ‘high-grade,’ or more aggressive, and have a greater chance of being invasive.

Compared with mammography, MRI doubled the overall sensitivity of detecting DCIS and doubled the sensitivity of diagnosing high-grade DCIS as well, reported Dr. Christiane K. Kuhl, vice chairman and professor of radiology at the University of Bonn, Germany.

"High-grade DCIS is important to diagnose" because it can be easily cured with surgery, noted Kuhl. However, "if left untreated, it will progress to high-grade invasive cancer."

Kuhl and colleagues investigated the sensitivity of high-resolution MRI and state-of-the-art mammography for diagnosing DCIS. Among more than 5,000 women in the study, 167 had a confirmed diagnosis of DCIS.

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

MRI also identified 98 per cent of the high-grade DCIS, whereas mammography identified only 52 per cent of the high-grade DCIS.

MRI identified 85 per cent of non-high-grade DCIS and mammography spotted 61 per cent of non-high grade DCIS.

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

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

Dr. Julie Gralow, of the University of Washington and moderator of the press briefing, commented: "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.