Efficacy of targeted chemokine receptor 4 PET/CT in evaluating active lesions in multiple myeloma, comparison to 18F-FDG PET/CT.

BACKGROUND: To compare the performance between chemokine receptor 4 (CXCR4) targeting PET/CT and 18F-Fluorodeoxyglucose (FDG) PET/CT in detecting active tumors in newly diagnosed (ND) and post-treated (PT)multiple myeloma (MM) patients. METHODS: 53 MM patients were recruited, comprising 10 NDMM and 43 PTMM. All patients underwent 68Ga-Pentixafor PET/CT, and 30 patients additionally received 18F-FDG PET/CT within one week. A positive focal lesion for visual analysis was defined as a lesion with a diameter greater than 5 mm, exhibiting uptake exceeding that of the surrounding normal bone tissue. Diffuse bone marrow uptake was characterized as homogeneous bone marrow uptake that was higher than liver. The number of lesions was recorded according to nine skeletal regions plus extramedullary sites. The maximum standard uptake values (SUVmax) and target to background ratios (TBR) of the most significant lesions in each region were calculated for semi-quantitative analysis. All patients provided samples from bone marrow or extramedullary tissues, with biopsy results confirming plasmacytoma or plasma cell analysis identifying monoclonal plasma cells ≥ 10% serving as the gold standard for the presence of active tumors. RESULTS: 68Ga-Pentixafor demonstrated a higher sensitivity than 18F-FDG in the overall sample (95.8% vs. 81.3%), NDMM (90% vs. 77.8%) and PTMM (100% vs. 85.7%). In head-to-head comparisons, 68Ga-Pentixafor detected more lesions than 18F-FDG in all regions. The SUVmax and TBR of 68Ga-Pentixafor were significantly higher than those of 18F-FDG (p < 0.001). In 68Ga-Pentixafor, the lesions in NDMM exhibited significantly lower SUVmax and TBR compared to those in PTMM (p < 0.05). There was no significant difference in FDG uptake between NDMM and PTMM lesions. CONCLUSION: 68Ga-Pentixafor demonstrates superior performance in detecting active lesions in both newly diagnosed and post-treated MM patients than 18F-FDG. CXCR4-targeted PET/CT may serve as a promising tool for diagnosing and monitoring treatment response of MM.