Utility of apparent diffusion coefficient as an imaging biomarker for assessing the proliferative potential of invasive ductal breast cancer

Aim To determine the clinical utility of apparent diffusion coefficient (ADC) metrics for the non-invasive assessment of tumour proliferation indicated by Ki-67 labelling index (LI) in invasive ductal breast cancer. Materials and methods Eighty patients with 80 histopathologically proven invasive ductal breast cancers underwent diffusion-weighted imaging with b-values of 0 and 800 s/mm 2 at a 3-T system. ADC metrics including ADC mean , ADC median , ADC min , ADC max , and ΔADC (ADC max –ADC min ) were recorded from the entire tumour volume on ADC maps, and correlated with the Ki-67 LI. Ki-67 staining of ≥14% was considered to indicate high proliferation and Results ADC min , ADC max , and ΔADC showed significant correlations with the Ki-67 LI (for all tumours, r = – 0.311, 0.436, and 0.551, respectively; for luminal/human epidermal growth factor receptor 2 (HER2)-negative group, r = – 0.437, 0.512, and 0.639, respectively; all p mean and ADC median showed no significant correlation (both p >0.05). Receiver operating characteristic (ROC) curve analysis for the differentiation of high- from low-proliferation groups showed that ΔADC yielded the highest area under the ROC curve for the whole tumour population (0.825; 95% confidence interval [CI]: 0.724, 0.901), as well as for the luminal/HER2-negative group (0.844; 95% CI: 0.692, 0.940). Conclusion ΔADC may serve as a promising imaging biomarker for the prediction of Ki-67 proliferation status in invasive ductal breast cancer.