Evaluation of Chemokine Receptor-4 Expression by 68Ga-Pentixafor PET/CT in Patients with Multiple Myeloma

The aim of this study to demonstrate and compare the CXCR4 expression by means of 68Ga-Pentixafor PET/CT in patients with multiple myeloma with standard clinical parameters and 18F-FDG PET/CT findings. Twenty-four (17 women, 7 men; mean age: 58.9 +/- 12.7) multiple myeloma patients who had undergone 18F-FDG PET/CT imaging to evaluate the disease activity were included in the study. 68Ga-Pentixafor PET/CT imaging was performed within an average period of 12 days after initial 18F-FDG PET/CT imaging. 68Ga-Pentixafor PET and 18F-FDG PET/CT revealed focal pathological lesions in 13/24 (54%) and 16/24 (67%) patients, respectively. In 19/24 patients, both tracers showed concordant findings (CXCR4+ and FDG+ in 12 patients; CXCR4- and FDG- in 7patients). In the remaining 5 patients, findings were discordant. The number of focal lesions identified by means of 68Ga-Pentixafor and 18-FFDG were 89 (44%) and 113 (56%), respectively. 68Ga-Pentixafor PET/CT showed more lesions in 2/12 (17%) patients, whereas 18F-FDG PET/CT was proved to be superior in 7/12 (58%) patients. In the remaining 3/12 (25%) patients, both tracers detected an equal number of lesions. There was no significant difference in appendicular and axial skeletal and extramedullary distribution ratios for both PET/CT examinations (p> 0.05). There was no statistically significant correlations between the 68Ga-Pentixafor PET/CT and 18F-FDG PET/CT positivity and disease activity, MM subtype, ISS phase, light chain disease, beta2microglobulin, albumin, creatinine, LDH, FLC and M protein levels in during scans. 68Ga-Pentixafor PET/CT cannot replace 18F-FDG PET/CT for diagnostic imaging of patients with multiple myeloma, 68Ga-PET/CT seem to be a valuable probe for patient stratification in the context of CXCR4-targeted radioligand therapy.