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MRI for Diagnosis of Breast Ductal Carcinoma In Situ
Abstract & Commentary
By Leon Speroff, MD, Editor, Professor of Obstetrics and Gynecology Oregon Health and Science University, Portland, is Editor for OB/GYN Clinical Alert.
Synopsis: MRI is more sensitive than mammography for the diagnosis of breast cancer when it is in the stage of ductal carcinoma in situ.
Source: Kuhl CK, et al. MRI for diagnosis of pure ductal carcinoma in situ: a prospective observational study. Lancet. 2007;370:485-492.
Kuhl and colleagues from the University of Bonn, Germany, compared the sensitivity of mammography and MRI for the diagnosis of breast ductal carcinoma in situ (DCIS).1 Seven thousand three hundred and nineteen women received both screening tests. In 167 women with ductal carcinoma in situ, 93 (56%) were diagnosed by mammography and 153 (92%) by MRI. Eighty-nine high-grade ductal in situ cancers were all diagnosed by MRI, but 43 (48%) were missed by mammography. The authors concluded that MRI is more sensitive in diagnosing breast DCIS.
Ductal carcinoma in situ is a precursor of invasive breast cancer, with progression occurring more often and more rapidly with higher grade in situ lesions, and the subsequent invasive disease is of a higher grade with a poorer prognosis. Diagnosis of higher grade ductal carcinoma in situ is, therefore, highly desirable. Mammography has led to an increase in the diagnosis of DCIS from 2% of breast cancers in 1980 to 20% today.
Earlier studies concluded that MRI was no better, and even worse, than mammography in diagnosing DCIS, and thus, the results in the current report were unexpected. However, it has been learned that diagnostic criteria differ with the two techniques, incorporating not only morphology but enhancement kinetics with contrast during MRI. MRI does not just detect cases of DCIS at an earlier stage, but this method detects lesions without microcalcifications (a different group of tumors). Mammography detects cases of DCIS that have microcalcifications caused by necrosis.
One of the important messages of this report is that both film screen mammography and digital mammography have limited sensitivity for diagnosing DCIS (determined by the size of microcalcifications). Another important message is that MRI was better for the detection of the higher grade DCIS associated with worse prognosis. The reason for this is the contribution of contrast enhancement. Tissues with higher grade lesions will have greater capillary permeability and an increase in microvasculature, accounting for more contrast enhancement. It is also important to note that an analysis of risk factors (including breast density) in the current report could not differentiate those subjects where mammography would or would not detect DCIS.
The availability of MRI in general population screening is currently limited by an insufficient number of radiologists with the required level of expertise. Therefore the results in the current report are likely not achievable in many centers. Having said that, there are an increasing number of specialty centers with the expertise and technology to perform accurate MRIs. The full use of MRI to detect breast cancer at its earliest stage awaits the results of a large multicenter trial that is obviously now indicated.