Whole-body diffusion-weighted MRI for evaluation of response in multiple myeloma patients following bortezomib-based therapy: A large single-center cohort study

Purpose: To determine the feasibility of whole-body diffusion-weighted imaging (WB-DWI) MRI for evaluation of response in patients with multiple myeloma (MM) following bortezomib-based therapy and to explore the direction of apparent diffusion coefficient (ADC) changes upon treatment. Method: Seventy-two MM patients who underwent WB-DWI MRI before and after bortezomib-based chemotherapy (21 weeks) were evaluated retrospectively. The estimated tumor volume (eTV) and ADC(mean) values before and after chemotherapy were calculated and compared between deep and non-deep responders. Predictive value of baseline ADC(mean) was calculated to predict the trend of ADC(mean) change following treatment. Results: Fifty-five patients were classified as deep responders, and 17 cases were assigned as non-deep responders. For 327 focal lesions (FLs), the ADC(mean) value was significantly increased from baseline to posttreatment. However, the ADC(mean) value was significantly decreased following treatment in 846 representative diffuse lesions. Diffuse lesions showed a significantly decreased ADC(mean) value in deep responders, whereas no significant variation in ADC(mean) value in FLs was found between deep and non-deep responders. Baseline ADC(mean) at a specific value (0.808 x 10(-3) mm(2)/s) yielded a maximum specificity (68.05%) and sensitivity (54.09%) in predicting increase of post-treatment ADCmean. Conclusions: The ADC(mean) value was significantly decreased in MM patients with diffuse pattern, while it was significantly increased in those with focal pattern following bortezomib-based treatment. WB-DWI MRI could be used to discriminate deep response to induction treatment in MM patients with diffuse infiltration pattern. Baseline ADC(mean) value might have a potential to predict the trend of ADC(mean) change following treatment.