Comparison of MR Cytometry Methods in Predicting Immunohistochemical Factor Status and Molecular Subtypes of Breast Cancer

Abstract

Background. First evaluation of the performance of MR cytometry incorporating transcytolemmal water exchange in predicting immunohistochemical factor status and molecular subtypes of breast cancer.

Materials and methods. 90 breast cancer patients were prospectively enrolled. For each participant, pulsed gradient spin-echo (PGSE) and oscillating gradient spin-echo (OGSE) diffusion-weighted imaging of 25Hz and 50Hz were performed on a 3T MRI scanner. Time-dependent apparent diffusion coefficients (ADC) and microstructural parameters including cell diameter d, intracellular volume fraction v_in, water exchange rate constant k_in, and apparent extracellular diffusivity D_ex were calculated. Single- and multi-variable logistic regression analysis were performed to evaluate their performance in identifying IHC factor status and molecular subtypes. The area under the receiver operating characteristic curve (AUC) was computed.

Results. The multi-variable regression models generated from MR cytometry-derived metrics provided higher AUC compared to those from time-dependent ADC metrics, i.e. 0.744 vs. 0.645 for ER, 0.727 vs. 0.688 for PR, 0.734 vs.0.623 for HER2, and 0.679 vs. 0.633 for Ki67, 0.751 vs. 0.644 for TNBC, 0.819 vs. 0.765 for HER2-enriched, 0.730 vs.0.659 for Luminal A, 0.633 vs.0.633 for Luminal B. MR cytometry with transcytolemmal water exchange (JOINT and EXCHANGE) outperformed the original one with the impermeable model (IMPULSED) in predicting PR (0.727 vs. 0.705), HER2 (0.734 vs. 0.689), Ki67 (0.679 vs. 0.646), TNBC (0.751 vs. 0.748) and HER2-enriched (0.819 vs. 0.739), Luminal A (0.730 vs. 0.666), Luminal B (0.633 vs. 0.630).

Conclusions. MR cytometry outperformed conventional ADC measurements in clinical breast cancer subtyping. Incorporating transcytolemmal water exchange further enhanced classification accuracy.