Differential diagnostic value of 18F-FDG PET/CT in multiple myeloma and unknown osteolytic metastasis / 中华核医学与分子影像杂志

ABSTRACT

Objective:To investigate the differential diagnostic value of 18F-FDG PET/CT in multiple myeloma (MM) and unknown osteolytic metastasis (UOM). Methods:A retrospective study was performed on 18F-FDG PET/CT imaging of 43 patients (29 males, 14 females, age (61.5±12.9) years) with multiple bone destructions and without extraosseous primary malignant tumor between June 2017 and March 2020 in Tenth People′s Hospital of Tongji University. Through follow-up, 20 patients (13 males, 7 females, age (61.1±12.2) years) were pathologically confirmed as MM and 23 patients (16 males, 7 females, age (61.4±13.9) years) were pathologically confirmed as UOM. The whole body skeleton was categorized to 8 sites including skull, spine, ribs, pelvis, sternum, clavicle, scapula and limb bone. The differences of the cross-sectional length of the lesion, cortical bone damage, SUV max and the distribution of imaging agent were compared between the two groups in different parts. Independent-sample t test and Mann-Whitney U test were used to analyze data. Results:The UOM group was invisible on clavicles, and spine and pelvis were the most predilection sites in both MM and UOM groups (spine 41.30%(299/724) and 49.37%(117/237); pelvis 24.45%(177/724) and 26.58%(63/237)). The cross-sectional length of lesions in the skull, spine, ribs, pelvis and limb bone in MM group were significantly shorter than those in UOM group (5.45(4.30, 8.06) vs (13.89±11.66) mm, 6.15(3.89, 10.06) vs 11.48(7.73, 16.90) mm, 7.01(4.59, 10.56) vs (24.61±16.22) mm, 8.20(5.14, 13.71) vs (21.12±13.31) mm, (8.48±5.75) vs (19.13±14.26) mm; z values from -8.88 to -2.52, t=-2.76, P<0.001 or P<0.05) and SUV max of above lesions and scapula in MM group were significantly lower than those in UOM group (1.50(1.00, 2.20) vs 17.15±11.40, 2.60(2.00, 4.10) vs 8.20(5.65, 11.90), 2.30(1.40, 5.28) vs 10.58±5.52, 2.50(1.80, 3.90) vs 9.34±6.01, 3.08±2.41 vs 11.38±6.38, 2.45(1.50, 4.43) vs 6.90(4.63, 17.80); z values from -13.87 to -2.41, t=-4.85, P<0.001 or P<0.05). The imaging agents in lesions on the skull, spine, ribs, pelvis, scapula and limb bone were more evenly distributed in MM group, while the imaging agents in lesions were more unevenly distributed in UOM group. On the skull, spine and ribs sites, the MM group was more likely to show no cortical bone damage; however, the UOM group showed cortical bone damage in the above sites. Conclusion:It is helpful for doctors to distinguish MM and UOM by comparing the cross-sectional length of the lesion, cortical bone damage, SUV max and the distribution of imaging agent in 18F-FDG PET/CT imaging before getting pathologic results.