MRI Screening Improves Detection of Hereditary Breast Cancer

CHICAGO—Magnetic resonance imaging (MRI) mammography was able to detect eight of nine breast malignancies, some of which had been missed on conventional film mammography, in 196 young women at high risk for hereditary breast cancer.

The only cancer missed by MRI mammography was a ductal carcinoma in situ (DCIS), reported Rene S. Shumak, MD, of the Department of Medical Imaging, Sunnybrook & Women’s College Health Sciences Centre, Toronto.

In her presentation at the 86^th Annual Meeting of the Radiological Society of North America (RSNA), Dr. Shumak said that women who are at risk for hereditary breast cancer because they carry a gene mutation for breast cancer or have a personal or very strong family history of the disease have a 50% chance of developing cancer by age 50 and an 85% chance by age 80.

Dense Breast Tissue

Breast cancer among high-risk women often occurs at a young age when breast tissue is dense. Conventional mammography is of limited effectiveness, therefore.

Dr. Shumak and her associates tested MRI mammography in 196 high-risk women over the course of a year. These included 96 women who were carriers of a breast cancer gene mutation, 17 who had a first-degree relative with a breast cancer gene mutation, and 83 who had a strong family history of breast cancer.

The first 65 women in the study had MRI mammography using a dedicated bilateral breast coil to obtain bilateral coronal images; the remaining women had MRI mammography done with sagittal images. Whenever an abnormality was found on initial MRI breast screening, the woman returned for follow-up high-resolution, dynamic, fast and delayed fat-saturated MRI.

Nine Cancers Detected

In this study, nine breast cancers were detected: All were 1.5 cm or less in size, and all were node negative. MRI mammography detected eight of the nine cancers, compared with two for clinical breast examination, four for mammography, and five for ultrasound.

Of 12 patients who underwent biopsy based solely on MRI findings, 2 were found to have breast cancer. In two cases, at biopsy the lesion could not be seen on directed ultrasound and required MRI-guided wire localization.

When compared with ultrasound and mammography, only MRI was able to pick up those cases involving dense glandular tissue and a small lesion (less than 0.5 cm). Ultrasound found larger lesions with dense glandular tissue, and mammography spotted lesions in breasts with less dense glandular tissue.

One 46-year-old woman with a BRCA1 gene mutation and highly dense breasts had no detectable abnormality on mammography. On MRI mammography, the first image obtained after administration of a contrast agent showed an oval, rapidly enhancing lesion. With some washout of the contrast medium, on the fourth image obtained after contrast administration, an enhanced rim around a malignancy persisted, and this lesion proved to be invasive carcinoma.

A 50-year-old women with a BRCA1 mutation and slightly less dense breast tissue had a small focally enhancing lesion on an initial MRI mammography scan and a rim-enhancing lesion on a high-resolution image. Subsequent directed ultrasound uncovered a hypoechoic 0.5-cm carcinoma.

Dr. Shumak concluded that MRI can detect breast malignancies that are missed by mammography, clinical breast examination, and screening ultrasound. Although directed ultrasound is a very effective method for targeting abnormalities that are found on MRI mammography, MRI-guided biopsy sometimes is needed to sample tissue from suspicious areas of breast tissue.