Prediction of axillary nodal burden using preoperative magnetic resonance imaging scoring in patients with clinically node-negative breast cancer: a retrospective cohort study.

Background: Axillary lymph node metastasis (ALNM) is a significant predictor of overall patient survival; thus, precise evaluation of ALNM is essential for staging breast cancer, informing multimodal treatment strategies, and ensuring optimal patient care. This study aimed to establish a magnetic resonance imaging (MRI) scoring system for predicting extensive axillary nodal metastasis in patients with clinically node-negative breast cancer derived from preoperative breast and axillary MRI.

Methods: This study included 226 patients with clinically node-negative breast cancer who underwent preoperative breast and axillary MRI between January 1, 2010 and December 31, 2020 at King Chulalongkorn Memorial Hospital. Their clinical, radiological, and pathological features were retrospectively reviewed. MRI characteristics of breast tumors and axillary lymph nodes (LNs) were assessed. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and Cohen's Kappa coefficient of the scoring system were evaluated. The receiver operating characteristic curve was used to determine the cutoff value for the MRI scoring system to differentiate extensive ALNM from nonextensive ALNM.

Results: Of the 226 patients, 144 had cancer-free axilla, 51 had 1-2 positive metastatic LNs, and 31 had ≥3 positive metastatic LNs. Moreover, only 60 could be evaluated for the apparent diffusion coefficient (ADC) value of LNs because of size limitations. The cutoff value for the MRI scoring system with ADC was 14 (NPV =87.1% with moderately acceptable discrimination), and the cutoff value without ADC was 8 (sensitivity =77.4%; specificity =81%; PPV =39.3%; NPV =95.8% with moderately acceptable discrimination).

Conclusions: The MRI scoring system using breast and axillary LN characteristics from preoperative MRI may help predict extensive ALNM and aid axillary nodal treatment selection.