Quantitative MRI biomarker for treatment response assessment of multiple myeloma - robustness evaluation using independent test set of prospective cases.

We are developing quantitative radiomic biomarkers for treatment response assessment of multiple myeloma (MM) in MRI. In our previous study, we have developed a 3D dynamic intensity entropy transformation (DIET) method with MRI for deriving a radiomic biomarker for differentiating responders from non-responders in treatment of MM. DIET transforms MR signal voxel by voxel to a quantitative entropy enhancement value (qEEV), from which predictor variables are extracted and combined into a qEEV-based response index (qERI) for quantitative assessment of treatment response. We developed the qERI in a previous retrospective data set of 64 MRI cases. This study evaluated the performance of the qERI-based MRI biomarker using an independent test set of 15 MRI cases collected from an ongoing prospective study, in which 10 and 5 patients were clinically diagnosed as responders and non-responders. The results showed that the agreement between the qERI prediction and the clinical outcome reached 0.80 with a kappa value of 0.57. The area under the ROC curve (AUC) achieved 0.78.