Is the MRI Phenotype Associated with Survival in Patients with Different Breast Cancer Subtypes?

Background: Breast cancer exhibits marked molecular and phenotypic heterogeneity, with important implications for prognosis and therapeutic response. Although magnetic resonance imaging (MRI) is widely used for detection and staging, its potential role as a prognostic biomarker across molecular subtypes remains incompletely understood. This study aimed to evaluate the association between MRI-defined tumor imaging phenotypes and disease-free survival (DFS) among different breast cancer molecular subtypes. Methods: This retrospective single-center study included 407 patients with invasive breast carcinoma of no special type who underwent pre-treatment breast MRI between October 2015 and May 2021. Tumors were classified into molecular subtypes and three MRI phenotypes based on lesion morphology and distribution. Associations between imaging phenotype, molecular subtype, and DFS were assessed using Kaplan–Meier analysis and Cox proportional hazards models. Results: Type 3 was the most prevalent imaging phenotype overall (60%), followed by Type 2 (21.9%) and Type 1 (18.2%). Imaging phenotype distribution differed significantly among molecular subtypes. Over a median follow-up of 57 months, imaging phenotype was not associated with DFS in Luminal A, Luminal B, or HER2-overexpressed tumors. However, in the triple-negative/ER-low subgroup, imaging phenotype demonstrated an independent association with DFS. In multivariable analysis, patients with the Type 1 phenotype had an 8.16-fold higher risk of recurrence compared with those with the Type 2 phenotype (95% CI: 1.49–44.60; p = 0.015). Type 2 lesions showed the most favorable survival outcomes. Conclusions: In this exploratory analysis, MRI phenotype was associated with disease-free survival in triple-negative and ER-low breast cancers. Circumscribed, unifocal tumors are associated with improved survival, whereas spiculated or multifocal patterns are associated with worse outcomes. However, given the small number of events in this subgroup, these exploratory findings need to be confirmed in larger studies before MRI morphology can be considered a prognostic imaging biomarker in aggressive breast cancer subtypes.