Early Phase Contrast Enhancement Dynamics of Breast Lesions of Different Molecular Subtypes Characterized by a Computer-Aided-Diagnosis System

PURPOSE: To evaluate early-phase contrast enhancement biomarkers computed by a computer-aided diagnosis (CADx) system to distinguish between different molecular subtypes of invasive breast lesions, imaged with a high spatiotemporal resolution view-sharing Dynamic Contrast Enhancement (DCE)-MRI protocol. METHOD AND MATERIALS: We collected images of 164 (21 basal, 24 HER2+ and 119 ER/PR+) invasive breast cancer lesions from 145 patients. Our MRI protocol provided 20 images of contrast-agent uptake each 4.3 seconds apart. A CADx system was developed to characterize the lesions based on early-phase contrast uptake dynamics. This CADx system was composed of four main steps. First, the lesion was segmented using manually placed seed points. Second, the aorta was automatically detected in the MR volume and initial time of enhancement in the aorta was computed. Third, for each voxel, contrast uptake data was fit to an exponential model and six dynamic features were computed based on this curve. These features were computed with respect to the first time point where the aorta starts to enhance. For each feature, we computed mean and standard deviation values in the entire segmented lesion. Additionally these features were computed in an automatically selected small hot-spot of the lesion (without standard deviation). This resulted in a total of 18 features characterizing the early phase dynamics. Finally, random-forests classifiers were trained and tested in a leave-one-out fashion in the study dataset in 3 different ways, to distinguish: (1) basal-type lesions from others, (2) HER2+ lesions from others and (3) ER/PR+ lesions from other type lesions. We evaluated performance for each classification using ROC analysis. We computed 5 percent confidence intervals for area under curve (AUC) values using a bootstrapping method. RESULTS: The AUC values for classification of basal-type/others, HER2+/others and ER/PR+/others were 0.68 (0.58-0.77), 0.62 (0.52-0.73) and 0.58 (0.49-0.68), respectively. CONCLUSION: A CADx system was used to distinguish between three different molecular subtypes of invasive breast lesions, where the highest performance was found in classification of basal type lesions from others. CLINICAL RELEVANCE/APPLICATION: Early phase contrast enhancement dynamics measured with DCE-MRI of the breast can be used to give an indication of molecular subtype for invasive breast cancer lesions. CADx systems can be used for this purpose.