Relationship Between Fluorine-18 Fluorodeoxyglucose PET/CT Uptake and the Plasma Cell Infiltration Rate in the Bone Marrow of Patients With Multiple Myeloma

Abstract Background: The present study investigated the relationship between maximum standardized uptake values (SUVmax) on Fluorine-18 Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and the plasma cell (PC) proliferation percentage in the bone marrow (BM) of patients with multiple myeloma (MM).Material and methods: Patients clinically and pathologically diagnosed with MM between January 2012 and October 2019 were selected from the database of Dokkyo Medical University Hospital (DMU Hospital), Japan. Patients with other malignancies and those who received chemotherapy and radiation therapy or hematopoietic treatments in the previous 4 weeks and 2-3 months prior to PET/CT scans were excluded from the present study to avoid false uptake. We examined 60 patients (female: male; 27:33; 1:1.22) aged between 37 and 91 years; mean ± SD; 67.3 ± 10.2 years. Hematological and biochemical tests with results on hemoglobin (Hb), hematocrit (Ht), C reactive protein (CRP), beta-2 microglobulin (b2m), creatinine (Cre), albumin (Alb), calcium (Ca), white blood cells (WBC), and red blood cells (RBC) were recorded and evaluated. The percentage of PC in BM biopsy samples was calculated. On PET/CT images, the SUVmax of the region of interest (ROI) of the right anterior iliac crest, the biopsy site, was measured. Relationships were examined using Pearson’s correlation coefficient with SPSS.Results: The types of MM diagnosed were IgGk in 31 patients (51.6%), IgGλ in 19 (31.6%), IgAλ in 5 (8.3%), IgAk in 2 (3.3%), IgDλ in 2 (3.3%), and IgDk in 1 (1.6%). According to the Durie-Salmon staging system, 4 patients had stage I, 6 stage II, and 33 stage III, while stages were not recorded in the remaining 17 patients. A positive correlation was observed between FDG uptake and the percentage of PC (r=0.7, p<0.001), but not between FDG uptake and hematological and biochemical parameters in all patients. However, a correlation was observed between FDG uptake and b2m (r=0.596, p=0.004) in 21 patients (35%).Conclusion: Increased FDG uptake by BM correlated with the percentage of PC. PET/CT is crucial for the diagnosis, treatment evaluation, and follow-up of MM patients.