Development of a Semiquantitative Whole-Body MRI Scoring System for Multiple Myeloma

Background: In patients with multiple myeloma (MM), the serum marker beta 2-microglobulin does not always accurately reflect tumor load. In contrast, whole-body (WB) MRI has shown high sensitivity for detecting bone lesions. Purpose: To develop and validate a semiquantitative WB MRI scoring system for newly diagnosed MM and to compare it with the International Staging System (ISS) and Revised ISS (R-ISS). Materials and Methods: This study included two retrospective groups (group 1, July 2015 to September 2021; group 2, February 2020 to September 2021) and one prospective group (group 3, October 2021 to February 2022) of patients with newly diagnosed MM. A new scoring system for MM was developed using spine MRI scans in group 1 and WB MRI scans in group 2 that integrated three features: (a) background marrow pattern, (b) number of focal bone lesions, and (c) presence of extramedullary or paramedullary lesions. The summed total score ranged from zero to nine. The interobserver agreement for each feature was assessed using Fleiss or Cohen weighted kappa. WB MRI total scores in group 3 were compared across ISS and R-ISS stages using two-way analysis of variance. Results: Groups 1, 2, and 3 included 103 patients (mean age, 62.1 years +/- 9.1 [SD]; 60 men), 36 patients (mean age 65.4 years +/- 11.3 [SD]; 19 women), and 39 participants (mean age, 62.0 years +/- 11.7 [SD]; 20 men), respectively. The interobserver agreements for the three features composing the scoring system were substantial (kappa range, 0.69-0.80). WB MRI total score increased with increasing ISS stage (mean score for ISS 1, 2, and 3 was 2.2, 4.2, and 5.8, respectively; P = .009) and R-ISS stage (mean score for R-ISS 1, 2, and 3 was 2.1, 3.8, and 5.9, respectively; P = .005). Conclusion: The developed WB MRI scoring system for MM demonstrated substantial observer agreement and corresponded well with ISS and R-ISS stages. (c) RSNA, 2023