3-T MRI More Sensitive for Breast Cancer Detection

Similar to lower-magnet-strength machines, 3-T MRI is much more sensitive than mammography or sonography for the detection of breast cancer, although it is not as specific as the other two modalities.

The objective of a recent study was to determine the sensitivity and specificity of 3-T MRI of the breasts compared with mammography and sonography, and to correlate these results with established data for 1.5-T MRI.

Design
Retrospective study.

Methodology
During an 18-month study interval, patients who underwent mammography, breast ultrasound, and breast MRI were identified. Only patients who underwent breast MRI with 3-T magnets were included. Only high-risk patients were included, with high risk defined as BRCA positivity or a personal or family history of breast cancer.

All patients underwent MRI on the same machine utilizing the same protocol, and images were interpreted by an experienced radiologist who was not blinded to each patient’s imaging and clinical history. Lesions on MRI were categorized via BI-RADS criteria utilizing morphology and enhancement kinetics. Whether a biopsy was performed was recorded, and resultant pathology results noted.

Results
434 women with a mean age of 53 years were included in the study. When correlated with pathology results, 7.6% of the 868 breasts imaged contained malignant tumors. MRI features suggesting malignancy included the following: (1) mass with spiculated margin or rim enhancement; (2) clumped linear, segmental, or regional enhancement; or (3) non-masslike enhancement with rapid wash-out.

The sensitivities of MRI, mammography, and sonography were 100%, 81.8%, and 86.4%, respectively. The specificities were 93.9%, 99%, and 98.1%, respectively.

Of the MRI-detected lesions that were true-positive for breast cancer, 13.6% were mammographically and sonographically occult. When compared with published performance numbers of 1.5-T MRI, the sensitivity of 3-T was higher, but these two modalities had similar specificities.

Reviewer’s Comments
The study serves to demonstrate 3-T MRI as more sensitive than mammography and sonography, albeit less specific. Without the patients having undergone lower-magnet-strength MRI as well, a true direct comparison of 1-T and 1.5-T MRI with 3-T MRI cannot be assessed.

Those who are using 3-T MRI for detection in high-risk populations can find comfort in this data that their sensitivities are high. The problem of poor specificity of breast MRI, regardless of magnet strength, has not been addressed.

Author: Basil Hubbi, MD

Reference:
Elsamaloty H, Elzawawi MS, et al. Increasing Accuracy of Detection of Breast Cancer With 3-T MRI. AJR Am J Roentgenol; 2009; 192 (April): 1142-1148.

Breast