POSTER: MM-638 Role of the Combination of FDG-PET Plus Whole Body MRI for Staging Newly Diagnosed and Relapsed/Refractory Multiple Myeloma (MM): A Prospective Trial

Topic: 13. Myeloma and other monoclonal gammopathies - Biology & Translational Research Background:18F-fluorodeoxyglucose (FDG) PET with CT (FDG-PET/TC) and magnetic resonance imaging (MRI) are both imaging diagnostic tools adopted in diagnosis and/or response assessment in multiple myeloma (MM). As 2016 IMWG criteria state that detection of bone lesions (myeloma defining events) is essential for diagnosis of MM (especially when CT is negative) and/or for ruling out them in patients with high risk smoldering MM (HR-SMM) and a PET/TC is one of the techniques essential for detecting the presence of bone disease in the diagnosis of MM. MR is the major diagnostic tool for identifying extra- or para-skeletal manifestations and complications, namely pathological fractures and spinal cord compression, as well as diagnostic tool for MM when > 1 lytic lesion is detected. Whole-Body MRI (WB-MRI) is a cross-sectional imaging technique for the entire skeletal study with the advantage of higher soft-tissue contrast in comparison to traditional X-ray or CT scan, offering the opportunity to also visualize bone marrow appearance. Both techniques can be useful in newly diagnosed MM as well in relapsed setting. Aims: The integration of FDG-PET/TC and WB-MRI in the diagnosis of MM may results in higher accuracy to detect bone lesion compared to them alone. This could be translated into better outcomes if early detection of myeloma defining events leads to earlier induction or re-induction treatments. Methods: In our Institution, from January 2021 to January 2023, we performed a prospective trial enrolling 73 consecutive newly diagnosed and relapsed/refractory MM (median age 63 years - range 85-35), according to IMWG, in which WB-MRI was performed according to MY-RADS criteria in combination with FDG PET/CT. 31/73 (42%) had a newly diagnosed MM, 25/73 (34%) were in follow-up after autologous stem cell transplantation and 17/73 (23%) patients were affected by relapsed/refractory MM. Subsequently, in 2 cases WB-MRI were aborted and not diagnostic so patients were excluded from the final analysis. Results: In these 71 patients: 52/71 (73%) cases of concordance of WB-MRI and 18F PET-CT, 18/71 (25%) cases of discordance. In this group 15/18 (83%) cases FDG-PET/CT was negative and WB-MRI showed positive findings according to MYRADS criteria (5 micronodular pattern, 9 diffuse pattern e 1 focal pattern) (Figure 1 Newly diagnosed MM – diffuse pattern in WB-MRI, PET negativity), in 3/18 (17%) FDG-PET/CT was positive for focal lesions and WB-MRI was negative. IMWG criteria showed concordance with WB-MRI data in 16/18 (89 %), in 2/18 (11%) case of follow-up after autologous stem cell transplantation PET-CT showed a relapsed focal lesion while WB-MRI was negative. Accuracy of WB-MRI was 69/71 (97%), whilst PET-CT was 55/71 (77%). These results are in agreement with the literature data about the ability of WB-MRI to depict diffuse and micronodular pattern of bone marrow infiltration. Summary/Conclusion: Our preliminary results support a potential complementary role of WB-MRI and FDG PET/CT findings, on the management of patients with MM at both diagnosis and relapse. To date, there is no wide availability of WB-MRI because in concerning about costs and technical issues, but data are consistent with its possible future leading role in MM diagnostic work-up.Figure 1 Keywords: Myeloma, Multiple myeloma, MRI, FDG-PET