Predictive role of diffusion-weighted whole-body MRI (DW-MRI) imaging response according to MY-RADS criteria after autologous stem cell transplantation in patients with multiple myeloma and combined evaluation with MRD assessment by flow cytometry.

Background: Diffusion-weighted whole-body MRI (DW-MRI) is increasingly used in the management of multiple myeloma (MM) patients, but data regarding the prognostic role of DW-MRI imaging response after treatment are lacking. The Myeloma Response Assessment and Diagnosis System (MY-RADS) imaging recommendations recently proposed the criteria for response assessment category (RAC) with a 5-point scale in order to standardize response assessment after therapy, but this score still needs to be validated.

Methods: We investigated the prognostic role of RAC criteria in 64 newly diagnosed MM patients after autologous stem cell transplantation (ASCT), and we combined the results of MY-RADS with those of minimal residual disease (MRD) assessment by multiparametric flow cytometry (MFC).

Results: Superior post-ASCT PFS and OS were observed in patients with complete imaging response (RAC1), with respect to patients with imaging residual disease (RAC≥2): median PFS not reached (NR) versus 26.5 months, p = 0.0047, HR 0.28 (95% CI: 0.12-0.68); 3-year post-ASCT OS 92% versus 69% for RAC1 versus RAC ≥2, respectively, p = 0.047, HR 0.24 (95% CI: 0.06-0.99). Combining MRD and imaging improved prediction of outcome, with double-negative and double-positive features defining groups with excellent and dismal PFS, respectively (PFS NR vs. 10.6 months); p = 0.001, HR 0.07 (95%CI: 0.01-0.36).

Conclusion: The present study supports the applicability of MY-RADS recommendations after ASCT; RAC criteria were able to independently stratify patients and to better predict their prognosis and the combined use of DW-MRI with MFC allowed a more precise evaluation of MRD.