ASCOIn a breast cancer screening population, magnetic resonance imaging (MRI) was more effective than mammography in detecting ductal carcinoma in situ (DCIS), especially high-grade lesions that are most likely to progress, according to a German study reported at the 43rd Annual Meeting of the American Society of Clinical Oncology (abstract 1504).
Cristiane K. Kuhl, MD, professor of radiology, University of Bonn, Germany, noted that while mammography is the gold standard for diagnosing DCIS, there are rising concerns about the overdiagnosis of low-grade lesions that are not clinically meaningful. MRI has recently established itself as superior in the diagnosis of invasive cancer in high-risk women, but is considered inferior for DCIS detection. This has been based, however, on small studies with selection bias.
The prospective study included 7,319 women referred to a dedicated breast unit for screening or for diagnostic assessment (ie, an unselected cohort). Women underwent bilateral mammography with at least two views, plus spot compression views where appropriate, and high-resolution bilateral MRI.
A total of 167 women received the final pathologic diagnosis of pure DCIS. This included 44 low-grade lesions, 34 intermediate-grade lesions, and 89 high-grade lesions.
Of these women, 58% had been referred for regular mammography screening, 8% for high-risk screening, 26% for follow-up after breast cancer, and 7% for clinical symptoms. The majority (56%) were referred for MRI due to an abnormal mammogram. Of those with a normal mammogram, 17% were concerned women of average risk, 11% had MRI as follow-up after breast cancer, 5% were high-risk women, 3% had clinical symptoms, and 8% were referred because of a previous incidental finding on an MRI performed to explore a mammographic abnormality unrelated to the DCIS.
Women were assessed for mode of detection and the biologic profile of the DCIS (size, nuclear grading, hormone-receptor status, and HER2 status).
Of the 167 DCIS cases, the diagnosis was made only by MRI in 153 cases (92%), and only by mammography in 93 cases (56%) (P < .0001), Dr. Kuhl reported.