Demographics: A total of 139 histopathologically confirmed lesions from 94 women were included. The mean age of the patients was 58, with 34 women in the young subgroup (<50 years old) and 61 in the old subgroup (≥50). The distribution of ACR classification groups was 18 patients conforming to non-dense breasts (A and B) and 76 patients in dense breasts (C and D) subgroups.

Fig 9: Demographic Characteristics of our Sample © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

Background Parenchymal Enhancement (BPE): MRI demonstrated a higher degree of BPE compared to CEM, with median values of 2 vs 1 respectively, which showed a statistically significant (p=0.001) difference.

Table 1: Breast parenchymal enhancement (BPE) classification distribution for each technique in our patients. © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

Histologically, 23 benign and 116 malignant lesions were identified. Among the malignant lesions, 49 Luminal A-invasive ductal carcinoma (A-IDC), 31 luminal B-invasive ductal carcinoma (B-IDC), and 9 triple negative invasive ductal carcinoma (TN-IDC) were described.

Table 2: All histological subgroups of malignant lesions. © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

Distribution of the malignant lesions: 65 were classified as unifocal, 25 as multicentric, 24 as multifocal and 2 as bilateral.

Table 5: Distribution of lesions © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

Lesion classification for each technique: MRI showed 18 FP and 4 FN and CEM, 1 FP and 22 FN.

Table 3: 3a: global accuracy of lesion classification for 3b: global accuracy of lesion classification for CEM. True positive (TP), False positive (FP), False negatives (FN) and True negative (TN). © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

The global sensitivity to detect breast cancer was 96.6% for breast MRI vs 81,03% for CEM (p=0.001). Subgroup analysis:

- Age: a sensitivity of 97.6% for MRI vs 85.4% for CEM (p=0.06) in young women and a sensitivity of 96.1% for MRI vs 82.9% for CEM (p=0.075) in the old women group.

- Breast density: a sensitivity of 96.9% for MRI vs 81.6% for CEM in the high-density subgroup (p=0.006) was found, showing a higher sensitivity of MRI vs CEM with a general tendency to statistical significance.

Table 4: Global and Subgroup analysis of MRI vs CEM sensitivity. © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

ROC curves show an AUC of 0.85 for MRI and 0.89 for CEM in the global analysis. Subgroup analysis:

-AUC of 0.85 for MRI and 0.89 for CEM in the high-density breast subgroup

-AUC of 0.87 for MRI and 0.91 for CEM in the young subgroup

-AUC of 0.85 for MRI and 0.89 for CEM in the old women group.

Low-density breasts AUC was unassessable due to the low number of patients.

No significant differences were found between any of the aforementioned groups.

Fig 10: ROC Curve analysis for MRI vs CEM accuracy. Global and subgroups analysis based on age and breast density. © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

The box plots showed the discrepancies between size measurements performed on MRI or CEM and the measurements performed by pathologists on surgical specimens (n=78).

The mean differences for MRI and CEM were +3.35 and +4.04 mm respectively, finding no significant differences in the tumor size assessment (p=0.389), with a tendency to lesion size overestimation.

Fig 11: Size measurement discrepancy between MRI or CEM and the measurements performed by pathologists on surgical specimens. © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

Among the histology of the FN in each technique, MRI failed to detect 4 lesions (1 DCIS and 3 Luminal-A). On the other hand, CEM failed to detect a total of 22 tumors, including 5 DCIS (one of them measuring 45 mm), 8 Luminal A, and 9 Luminal B. Both techniques detected all Her 2 and TN carcinomas.

Fig 12: False Negatives with each technique deffinitive diagnosis. © Department of Radiology, Clínica Universidad de Navarra, Pamplona/ Spain 2024

Results are currently under review, pending for publication.