Apparent diffusion coefficient in estrogen receptor‐positive and lymph node‐negative invasive breast cancers at 3.0T DW‐MRI: A potential predictor for an oncotype Dx test recurrence score

Purpose To measure the apparent diffusion coefficient (ADC) values in estrogen receptor‐positive (ER+) and axillary lymph node‐negative (LN–) invasive breast cancer and investigate the correlation of ADC with Oncotype Dx test recurrence scores (ODxRS). Materials and Methods This was a Health Insurance Portability and Accountability Act (HIPAA)‐compliant single‐site retrospective study. Patients underwent preoperative 3.0T MRI scans with additional diffusion‐weighted imaging sequential scans (b = 0, 600 and b = 0, 1000 s/mm 2 ) from January 2011 to 2013. The study population included 31 ER+/LN– invasive breast cancers, which underwent ODxRS genomic testing. ADC 600 and ADC 1000 parametric maps were generated, and ADC values were calculated from a user‐drawn region of interest. ODxRS predicts 10‐year recurrence risk in individual patients: low (RS <18), intermediate (RS: 18–30), or high (RS >30). All breast lesions, including subgroups of invasive ductal carcinoma (IDC) lesions and mass‐only lesions were dichotomized by RS scores, low‐risk versus intermediate/high‐risk, and statistical analysis was performed using Mann–Whitney's test (statistical significance at P < 0.05) and receiver operating characteristic (ROC) curves. Multivariate analysis was also performed. Results Invasive breast cancers, when scored as low‐risk by ODxRS, had significantly higher ADC values compared with intermediate/high‐risk lesions for both ADC 600 ( P  = 0.007) and ADC 1000 ( P  = 0.008) mean values. This was true both when analyzing only mass‐lesions ( P  = 0.03 and 0.01) or only IDCs ( P  = 0.001 and 0.009). Conclusion Preliminary findings suggest that lesion ADC values correlate with recurrence risk likelihood stratified using ODxRS. Hence, ADC is a potential surrogate biomarker for tumor aggressiveness. Level of Evidence: 3 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2018;47:401–409.