Role of the combination of 3 T whole-body MRI and 18F-FDG PET/CT in the management of multiple myeloma and smoldering myeloma: The new era of imaging.

Abstract

7560 Background: FDG-PET/TC and MRI are both imaging diagnostic tools adopted in diagnosis and/or response assessment in multiple myeloma (MM) which can be useful in smoldering, newly diagnosed as well in relapsed myeloma. Methods: From January 2021 to January 2025, we enrolled into a prospective trial 139 consecutive patients (54 Male; mean age, 67 years ± 10 [SD]) divided into 3 groups; 34 had a newly diagnosed MM according to the IMWG (group 1); 20 were in follow-up after autologous stem cell transplantation with clinical or laboratory data suspicious for relapse or progression (group 2) and 38 were affected by relapsed/refractory MM during treatment (group 3). In addition we enrolled 47 patients newly diagnosed high risk SMM, according to IMWG (19 Male, mean age 59 years+-10 [SD]). Results: On a per-patient basis, 126/139 (90%) had concordant PET/CT and WB-MRI scans, while 13/139 (10%) had discordant scans in terms of positivity/negativity. Among concordant studies, 47/139 (34%) were negative with both imaging methods while 93/139 (67%) were positive at both (including FLs and/or BMI). Among discordant studies, 8/9 had a positive WB-MRI scan and a negative PET-CT scan (6 cases with BMI or micronodular involvement alone), whereas 1/9 had a positive PET-CT and a negative WB-MRI. PET/CT detected FLs pattern in 83/139 patients, WB-MRI alone identified FLs pattern in 6 patients. PET-CT led to a change of treatment approach in 72/139 patients (52%), WB-MRI in 84/139 patients (60%), the combination of the two methods led to a change of management in 86/139 (62%), highlighted in the case of suspected post-transplant relapse. Furthermore, WB-MRI led to a change of management for incidental findings in additional 9 patients (8 suspected malignancies and 1 spinal cord compression). Interim analysis in HR- SMM showed discordance between the results of the two imaging modalities in 32/139 (23%). WB-MRI detected BMI pattern without any overt focal lesion in 11 patients (only 1 correlated with PET/CT) and FLs pattern in 7 patients (4 confirmed also in PET/CT), while PET/CT detected an additional FLs pattern in 1 patient, without bone lytic lesion evidence at the CT images. Both methods led to 6 changes of management, whereas MRI alone led to a change of treatment approach in 14 patients (10%), 13 diagnoses and 1 accessory finding of suspected cholangiocarcinoma. Conclusions: Our preliminary data underlines the fundamental role of functional imaging in the evaluation of FLs and BMI in MM with a superior detection rate of WB-MRI related to the ability to identify diffuse and micronodular pattern. A potential complementary role of the two methods in clinical management could be suggested in suspicion of relapsed or progressing MM. Furthermore our prospective trial supports the utmost role of WB-MRI (performed according to MY-RADS) in the assessment of high risk Smoldering Myeloma.