Fast track — ArticlesMRI for diagnosis of pure ductal carcinoma in situ: a prospective observational study
Introduction
Although commonly held to be a direct precursor of invasive breast cancer, ductal carcinoma in situ (DCIS) is a heterogeneous disease.1 High-grade DCIS seems to progress to invasive breast cancer more often and more rapidly than does low-grade DCIS.2, 3, 4, 5, 6, 7 Molecular markers and genetic signatures indicate that high-grade lesions and low-grade lesions develop through distinct pathways, rather than by progressive dedifferentiation.8, 9, 10, 11 Whereas high-grade DCIS is likely to progress to high-grade invasive cancer, low-grade DCIS can be more indolent or might progress to only certain types of cancer, usually well differentiated. There is agreement in that DCIS should be treated (at least) by local excision to avoid recurrence or progression to invasive breast cancer.12, 13 Diagnosis of DCIS, especially high-grade DCIS, is therefore considered desirable in principle.
Before the advent of mammographic screening, DCIS used to be a rare diagnosis, making up only 2% of cancers treated in 1980.14 Today, about 20% of breast cancers are diagnosed in the pre-invasive stage.15, 16 Mammography is the mainstay for diagnosing DCIS, whereas other breast imaging techniques—eg, sonography, MRI, scintimammography, and positron emission tomography—have been previously shown to be unreliable.17 Specifically, a number of studies investigated the diagnostic yield of breast MRI in patients who, on the basis of the demonstration of mammographic microcalcifications, had been diagnosed with DCIS. The results of these studies were concordant in that MRI did not visualise all intraductal cancers that were mammographically apparent and thus MRI was deemed to be less sensitive than mammography for the diagnosis of pure intraductal cancer.18, 19, 20, 21, 22, 23 Accordingly, the use of breast MRI for diagnosing DCIS is mostly discouraged.24
In recent years, however, it has become evident that the diagnosis of intraductal cancer is feasible with MRI, although it requires diagnostic criteria that are different from those that are used to diagnose invasive cancer.25, 26, 27 Since these diagnostic criteria were published, our group and others have found that MRI does allow the prospective diagnosis of DCIS, and even allows the diagnosis of DCIS that could go undetected by mammography.28, 29, 30, 31, 32
Whether breast MRI can be used to diagnose DCIS prospectively if its use is not restricted to patients with mammographic abnormalities (especially microcalcifications) is unknown. Our aim was to compare the respective sensitivities of mammography and breast MRI, and to compare the biological profiles of DCIS detected by mammography with those detected by breast MRI.
Section snippets
Patients
Data were collected at the breast centre at the University of Bonn Hospital and Medical School, an academic tertiary care institution. The breast centre consists of the Departments of Gynaecological Oncology, Radiology, Pathology, and Radiation Oncology. The centre houses a breast cancer screening site and, as such, offers diagnostic assessment for its own screening participants and for patients with questionable or suspicious clinical or imaging findings identified elsewhere. The centre also
Results
Of the 7319 women who had undergone both mamography and MRI during the study period, 1208 (15%) women received a positive imaging diagnosis (BI-RADS 4 or 5). 574 of these women received a benign pathological result; 469 were finally diagnosed with invasive breast cancer, and 165 women had an imaging diagnosis of BI-RADS 4 or 5 and received the final pathological diagnosis of pure DCIS. Two further cases of DCIS were diagnosed on the basis of clinical symptoms only.
During the study period, 26
Discussion
Our study suggests that the sensitivity of film screen or digital mammography for diagnosing DCIS is limited. Of the 167 intraductal cancers that had been diagnosed during the study period, 72 (43%) were mammographically occult, but were diagnosed by MRI alone.
What are the diagnostic and prognostic implications of these mammographically occult lesions? Mammography tends to identify breast cancers with comparatively benign biological profiles, a fact referred to as length time bias.36, 37, 38
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