Application of the Kaiser score on contrast-enhanced mammography in the differential diagnosis of breast lesions: comparison with breast magnetic resonance imaging

Abstract

Background: The Kaiser score (KS) as a clinical decision rule has been proven capable of enhancing the diagnostic efficiency for suspicious breast lesions and obviating unnecessary benign biopsies. However, the consistency of KS in contrast-enhanced mammography (CEM-KS) and KS on magnetic resonance imaging (MRI-KS) is still unclear. This study aimed to evaluate and compare the diagnostic efficacy and agreement of CEM-KS and MRI-KS for suspicious breast lesions.

Methods: This retrospective study included 207 patients from April 2019 to June 2022. The radiologists assigned a diagnostic category to all lesions using the Breast Imaging Reporting and Data System (BI-RADS). Subsequently, they were asked to assign a final diagnostic category for each lesion according to the KS. The diagnostic performance was evaluated by the area under the receiver operating characteristic curve (AUC). The agreement in terms of the kinetic curve and the KS categories for CEM and MRI were evaluated via the Cohen kappa coefficient.

Results: The AUC was higher for the CEM-KS category assignment than for the CEM-BI-RADS category assignment (0.856 vs. 0.776; P=0.047). The AUC was higher for MRI-KS than for MRI-BI-RADS (0.841 vs. 0.752; P =0.015). The AUC of CEM-KS was not significantly different from that of MRI-KS (0.856 vs. 0.841; P=0.538). The difference between the AUCs for CEM-BI-RADS and MRI-BI-RADS was not statistically significant (0.776 vs. 0.752; P=0.400). The kappa agreement for the characterization of suspicious breast lesions using CEM-KS and MRI-KS was 0.885.

Conclusions: The KS substantially improved the diagnostic performance of suspicious breast lesions, not only in MRI but also in CEM. CEM-KS and MRI-KS showed similar diagnostic performance and almost perfect agreement for the characterization of suspicious breast lesions. Therefore, CEM holds promise as an alternative when breast MRI is not available or contraindicated.

Keywords: Breast neoplasms; clinical decision support system; contrast-enhanced mammography (CEM); diagnosis; magnetic resonance imaging (MRI).

Figure 1

The flowchart of patient inclusion. CEM, contrast-enhanced mammography; MRI, magnetic resonance imaging.

Figure 2

The KS flowchart of CEM. The diagnostic score is associated with an increasing probability of malignancy (1 = lowest, 10 = highest). BI-RADS, Breast Imaging Reporting and Data System; KS, Kaiser score; CEM, contrast-enhanced mammography.

Figure 3

The ROC curves for CEM and MRI. CEM, contrast-enhanced mammography; BI-RADS, Breast Imaging Reporting and Data System; MRI, magnetic resonance imaging; ROC, receiver operating characteristic.

Figure 4

A 50-year-old patient with a ductal carcinoma in situ (high nuclear grade) with microinvasion. MRI early contrast-enhanced phase showed (A) a segmental NME lesion with irregular margin, clustered ring enhancement, and (B) a plateau time-signal intensity curve corresponding to a KS of 5. (C) Early and (D) late RC images on CEM demonstrated a segmental NME lesion with irregular margin, heterogeneous internal enhancement, and (E) a plateau curve also corresponding to a KS of 5. MRI, magnetic resonance imaging; NME, non-mass enhancement; KS, Kaiser score; RC, recombined; CEM, contrast-enhanced mammography.

Figure 5

A 58-year-old patient with grade II invasive ductal carcinoma. (A) Perifocal edema was absent on T2WI. On MRI, the early contrast-enhanced phase showed (B) an irregular mass with spiculations, rim enhancement, and (C) a washout time-signal intensity curve corresponding to a KS of 9. (D) Early and (E) late RC images on CEM demonstrated an irregular mass with spiculations, rim enhancement, and (F) a washout curve also corresponding to a KS of 10. T2WI, T2-weighted imaging; MRI, magnetic resonance imaging; KS, Kaiser score; RC, recombined; CEM, contrast-enhanced mammography.

Figure 6

A 46-year-old patient with a fibroadenoma. On MRI, the early contrast-enhanced phase showed (A) an oval, circumscribed mass with heterogeneous internal enhancement and (B) a plateau time-signal intensity curve corresponding to a KS of 2. (C) Early and (D) late RC images on CEM demonstrated a circumscribed mass and (E) a plateau curve also corresponding to a KS of 2. MRI, magnetic resonance imaging; KS, Kaiser score; RC, recombined; CEM, contrast-enhanced mammography.