MRI Phenotype of Breast Cancer: Kinetic Assessment for Molecular Subtypes

Purpose: To evaluate the dynamic contrast-enhanced magnetic resonance imaging (MRI) kinetic characteristics of newly diagnosed breast cancer molecular subtypes. Materials and Methods: Breast MRI examinations of 112 patients with newly diagnosed breast cancer were reviewed. Cases of newly diagnosed invasive ductal carcinoma were sorted by molecular subtype (28 TN, 11 HER2+, 73 Lum A/ B) and MRI field strength, with lesion segmentation and kinetic analyses performed on a dedicated workstation. For kinetic assessment, 50% and 100% thresholds were employed for display of medium and rapid uptake. Kinetic profiles in terms of percent volume for six kinetic types (medium-persistent, medium-plateau, medium-washout, fast-persistent, fast-plateau, fast-washout) relative to the whole volume of the lesion were obtained. Statistical analysis of the kinetic profiles was performed using Welch's t-test. Results: Percent volume of HER2-positive lesions with >100% uptake at early phase on 3T strength MRI exams was significantly greater compared with luminal A/B (93.8 +/- 0.92 vs. 77.3 +/- 7.2; P<0.01) and triple negative (93.8 +/- 0.92 vs. 81.3 +/- 8.2; P<0.05) subtypes. The >50% early phase uptake for HER2+ lesions was also higher than Lum A/B (99.1 +/- 0.73 vs. 93.6 +/- 3.05; P<0.01) at 3T. In the 1.5T subgroup the percent volume of HER2+ tumors with >50% and >100% early phase uptake trended higher than Lum A/B lesions without reaching significance. Conclusion: The percent volume of HER2-positive tumors demonstrating rapid early contrast uptake is significantly increased compared to other molecular subtypes.