A Study On Evaluating Treatment Response In Multiple Myeloma Using Whole-body Diffusion-weighted MRI

Objective:This study aimed to evaluate the value of apparent diffusion coefficient?ADC?from whole-body diffusion-weighted MRI?WB-DWI MRI?in the discrimination of deep response to induction and consolidation therapy in newly diagnosed multiple myeloma?NDMM?.Methods:Part I:17 NDMM patients were included and treated with four courses of bortezomib-based induction chemotherapy.All patients underwent WB-DWI MRI before and after induction therapy and 89regions of interest were chosen for the measurement of ADC.The patients were grouped by deep??VGPR?versus non-deep response?<VGPR?at the induction therapy and consolidation therapy,respectively.ADC and ADC percent changes after induction chemotherapy were compared between deep and non-deep responders.Diagnostic accuracy of ADC was calculated using ROC at specific cut offs.Predictive positive value?PPV?of ADC was calculated to predict deep response to consolidation therapy.Part II:A total of 50 lesions were obtained and analyzed?>=100 mm²,the largest three lesions in all lesions from each patient?from 17 NDMM patients in Part I.Morphological parameters?lesion size,signal intensity and number of lesions?were measured before-and-after induction therapy and compared between deep and non-deep responders.Results:Part I:Lesions reduced in size and number and signal intensity decreased in follow-up DWI,which did not differ between deep and non-deep responders.ADC in deep responders after induction therapy was significantly higher than in non-deep responders?P=0.03?.ADC percent changes were significantly higher in deep responders?36.79%?than in non-deep responders?11.50%?after induction therapy?P=0.02?.ADC percent increases by 46.96%,78.0%yielded specificity at 81.4%,90.7%in discriminating deep response to induction therapy.PPV predicting deep response to consolidation therapy was 62.0%by using ADC cutoff>1.00 x 10^-3 mm²/s at week 20.Part II:Cutoff values selected for percent change in signal intensity showed a moderate accuracy in the discrimination of deep response at the end of induction therapy?ROC AUC=0.64?.However,there was no significant difference in the variation of lesion size,lesion number and signal intensity before and after induction therapy between deep responders and non-deep responders.Conclusions:ADC and ADC percent changes increased remarkably in patients who achieved deep response at the end of induction chemotherapy,which represented a confirmatory diagnostic tool to discriminate deep response to induction therapy for patients with multiple myeloma.ADC may have a potential to predict deep response to consolidation therapy.Morphological assessments based on DWI images alone were not capable of discriminating depth of response to induction therapy.