The added diagnostic value of dynamic contrast-enhanced MRI at 3.0 T in nonpalpable breast lesions

Abstract

Objective: To investigate the added diagnostic value of 3.0 Tesla breast MRI over conventional breast imaging in the diagnosis of in situ and invasive breast cancer and to explore the role of routine versus expert reading.

Materials and methods: We evaluated MRI scans of patients with nonpalpable BI-RADS 3-5 lesions who underwent dynamic contrast-enhanced 3.0 Tesla breast MRI. Initially, MRI scans were read by radiologists in a routine clinical setting. All histologically confirmed index lesions were re-evaluated by two dedicated breast radiologists. Sensitivity and specificity for the three MRI readings were determined, and the diagnostic value of breast MRI in addition to conventional imaging was assessed. Interobserver reliability between the three readings was evaluated.

Results: MRI examinations of 207 patients were analyzed. Seventy-eight of 207 (37.7%) patients had a malignant lesion, of which 33 (42.3%) patients had pure DCIS and 45 (57.7%) invasive breast cancer. Sensitivity of breast MRI was 66.7% during routine, and 89.3% and 94.7% during expert reading. Specificity was 77.5% in the routine setting, and 61.0% and 33.3% during expert reading. In the routine setting, MRI provided additional diagnostic information over clinical information and conventional imaging, as the Area Under the ROC Curve increased from 0.76 to 0.81. Expert MRI reading was associated with a stronger improvement of the AUC to 0.87. Interobserver reliability between the three MRI readings was fair and moderate.

Conclusions: 3.0 T breast MRI of nonpalpable breast lesions is of added diagnostic value for the diagnosis of in situ and invasive breast cancer.

Figure 1. Craniocaudal (a) and mediolateral oblique (b) mammogram of a 52 year old patient with BI-RADS 5 microcalcifications in the left lateral upper quadrant.

Ultrasound imaging was unremarkable (BI-RADS 1). During routine reading, the MRI examination was classified as BI-RADS 4. Both expert reader 1 and 2 classified the lesion as an area of non-mass like enhancement with clumped internal enhancement and a segmental distribution. Kinetics showed a rapid initial rise and a plateau stage during the delayed phase. A BI-RADS 4 and 5 classification was given by expert reader 1 and 2, respectively. Figure 1 shows the dynamic contrast-enhanced MRI (c) and the MR image imported in the CAD software (d). The color-coded overlay indicates the type of enhancement after contrast injection in the late phase. Red, yellow and blue illustrate a washout-, plateau- and persistent- enhancement curve, respectively. Stereotactic biopsy and surgery both showed DCIS without an invasive component.

Figure 2. Craniocaudal (a) and mediolateral oblique (b) mammogram of a 40 year old, asymptomatic woman underwent mammography during follow-up after right-sided breast cancer, for which she underwent mastectomy.

Mammography showed BI-RADS 4 microcalcifications in the lateral upper quadrant of the left breast. Ultrasound imaging was unremarkable (BI-RADS 1). During routine MRI reading, a BI-RADS 1 classification was assigned. Expert reader 1 reported an area of non-mass-like enhancement with a diffuse distribution, heterogeneous internal enhancement and classified MR imaging as BI-RADS 4. In addition, expert reader 2 described an area of non-mass-like enhancement with a segmental distribution and clumped internal enhancement, and reported a BI-RADS 4. Kinetics showed a rapid initial rise and a plateau stage during the delayed phase. Figure 2 shows the dynamic contrast-enhanced MRI (c) and the MR image imported in the CAD software (d). The color-coded overlay indicates the type of enhancement after contrast injection in the late phase. Yellow and blue illustrate a plateau- and persistent- enhancement curve, respectively. Stereotactic biopsy showed normal breast tissue with minor fibrocystic changes and the extensive presence of microcalcifications.

Figure 3. ROC analysis shows an AUC of 0.76 for the model with clinical characteristics and conventional imaging, which is displayed as the green, dashed line in the three graphs (a-c).

The red, solid lines show the AUC's for the models after addition of MRI reading. The model for routine reading has an AUC of 0.81 (a), both models with expert MRI reading have an AUC of 0.87 (b-c).