Establishment of an interpretable MRI radiomics-based machine learning model capable of predicting axillary lymph node metastasis in invasive breast cancer

Abstract

This study sought to develop a radiomics model capable of predicting axillary lymph node metastasis (ALNM) in patients with invasive breast cancer (IBC) based on dual-sequence magnetic resonance imaging(MRI) of diffusion-weighted imaging (DWI) and dynamic contrast enhancement (DCE) data. The interpretability of the resultant model was probed with the SHAP (Shapley Additive Explanations) method. Established inclusion/exclusion criteria were used to retrospectively compile MRI and matching clinical data from 183 patients with pathologically confirmed IBC from our hospital evaluated between June 2021 and December 2023. All of these patients had undergone plain and enhanced MRI scans prior to treatment. These patients were separated according to their pathological biopsy results into those with ALNM (n = 107) and those without ALNM (n = 76). These patients were then randomized into training (n = 128) and testing (n = 55) cohorts at a 7:3 ratio. Optimal radiomics features were selected from the extracted data. The random forest method was used to establish three predictive models (DWI, DCE, and combined DWI + DCE sequence models). Area under the curve (AUC) values for receiver operating characteristic (ROC) curves were utilized to assess model performance. The DeLong test was utilized to compare model predictive efficacy. Model discrimination was assessed based on the integrated discrimination improvement (IDI) method. Decision curves revealed net clinical benefits for each of these models. The SHAP method was used to achieve the best model interpretability. Clinicopathological characteristics (age, menopausal status, molecular subtypes, and estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2, and Ki-67 status) were comparable when comparing the ALNM and non-ALNM groups as well as the training and testing cohorts (P > 0.05). AUC values for the DWI, DCE, and combined models in the training cohort were 0.793, 0.774, and 0.864, respectively, with corresponding values of 0.728, 0.760, and 0.859 in the testing cohort. The predictive efficacy of the DWI and combined models was found to differ significantly according to the DeLong test, as did the predictive efficacy of the DCE and combined models in the training groups (P < 0.05), while no other significant differences were noted in model performance (P > 0.05). IDI results indicated that the combined model offered predictive power levels that were 13.5% (P < 0.05) and 10.2% (P < 0.05) higher than those for the respective DWI and DCE models. In a decision curve analysis, the combined model offered a net clinical benefit over the DCE model. The combined dual-sequence MRI-based radiomics model constructed herein and the supporting interpretability analyses can aid in the prediction of the ALNM status of IBC patients, helping to guide clinical decision-making in these cases.

Keywords: Breast cancer; Combined model; Lymph node metastasis; Magnetic resonance imaging; Radiomics; SHAP.

Fig. 1

Patient selection strategy. DWI: diffusion-weighted imaging; DCE: dynamic contrast enhancement.

Fig. 2

A 41-year-old female with invasive carcinoma of no special type in the right breast, Luminal A subtype, without lymph node metastasis. (A, B) Original DWI images and a schematic overview of the outlining of the region of interest; (C, D) Original DCE images and schematic overview of the outlining of the region of interest.

Fig. 3

A 54-year-old female patient with invasive carcinoma of no special type in the left breast, HER-2 overexpression subtype, with lymph node metastasis. (A, B) Original DWI images and a schematic overview of the outlining of the region of interest; (C, D) Original DCE images and schematic overview of the outlining of the region of interest. Note: DWI is diffusion-weighted imaging and DCE is dynamic contrast enhancement imaging.

Fig. 4

ROC curves for the three radiomics models.

Fig. 5

Clinical decision curves for the three radiomics models.

Fig. 6

Bar lot for the combined model.

Fig. 7

Beeswarm plot for the combined model.