Comparison between breast MRI and contrast-enhanced spectral mammography

Abstract

Background: The main goal of this study was to compare contrast-enhanced spectral mammography (CESM) and breast magnetic resonance imaging (MRI) with histopathological results and to compare the sensitivity, accuracy, and positive and negative predictive values for both imaging modalities.

Material/methods: After ethics approval, CESM and MRI examinations were performed in 102 patients who had suspicious lesions described in conventional mammography. All visible lesions were evaluated independently by 2 experienced radiologists using BI-RADS classifications (scale 1-5). Dimensions of lesions measured with each modality were compared to postoperative histopathology results.

Results: There were 102 patients entered into CESM/MRI studies and 118 lesions were identified by the combination of CESM and breast MRI. Histopathology confirmed that 81 of 118 lesions were malignant and 37 were benign. Of the 81 malignant lesions, 72 were invasive cancers and 9 were in situ cancers. Sensitivity was 100% with CESM and 93% with breast MRI. Accuracy was 79% with CESM and 73% with breast MRI. ROC curve areas based on BI-RADS were 0.83 for CESM and 0.84 for breast MRI. Lesion size estimates on CESM and breast MRI were similar, both slightly larger than those from histopathology.

Conclusions: Our results indicate that CESM has the potential to be a valuable diagnostic method that enables accurate detection of malignant breast lesions, has high negative predictive value, and a false-positive rate similar to that of breast MRI.

Figure 1

Breast images of a 51-year-old patient (A) initial digital mammography; (B) breast MRI – T1 and T2 weighted images, contrast enhanced T1 dynamic images with fat saturation and subtraction image 5 minutes after contrast injection (a cyst visible in T1 and T2 weighted images, no other focal lesions determined, small foci of contrast enhancement visible on the cyst wall, although the shape of the enhancement curve is non-characteristic – considering all the features of the lesion determined in MRI examination, the lesion was interpreted to be benign BI-RADS 2); (C) the CESM images with area of contrast enhancement near the cyst in the left breast (BI-RADS 4); (D) Histopathology – Atypical lobular hyperplasia/LCIS.

Figure 2

Comparison of BI-RADS in MRI and CESM. BI-RADS diagnosis based on MRI and CESM were consistent and correct in 93% of detected and histopathology-proven cancers. The remaining 7% of the observed cancers were properly diagnosed on CESM and mistakenly assessed on MRI. The classification was incorrect for both techniques in 54% of benign lesions. Among benign lesions, MRI incorrectly classified 70% as BI-RADS 4 or greater, while CESM incorrectly classified 68% as BI-RADS 4 or greater. Lesions that proved to be benign on histopathological examination were correct and consistent in 16%.

Figure 3

Comparison of ROC curves for CESM (blue line) and MRI (dashed red line) based on BI-RADS scores. Dotted reference line represents the ROC curve for a random distribution of cases with negative and positive test results.