Objective To prepare and evaluate 99Tcm radiolabeled Cetuximab (C225) for imaging of EGFR specific binding.Methods Cetuximab antibody was reduced by 2-iminothiophene (2-IT).The radiolabeling of IT-Cetuximab with 99Tcm(99Tcm-IT-Cetuximab) was analyzed by HPLC,and was tested for in vitro stability and molecular integrity.The human lung cancer line (A549)-bearing nude mouse model was prepared for biodistribution and tumor targeted study.Tumor uptake was also measured by in vivo γ imaging.Results The labeling efficiency was 93.15％.The radiochemical purity was 96.46％ after purification.The in vitro stability was good in 5％ HSA,in which the radiochemical purity maintained above 80％ at 4 ℃ for 24 h.99Tcm-IT-Cetuximab showed good specific binding to tumor with peak uptake of (3.417±0.769) ％ID/g after 4 h.The T/NT ratio of blood increased to 1.454±0.174 at 24 h.γ imaging of A549-bearing nude mice xenografts also showed high T/NT ratio.Conclusions 99Tcm-IT-Cetuximab molecular probe could be prepared with high radiolabeling yield and radiochemical purity.It has excellent in vitro and in vivo stability,and shows specific uptake in A549 tumor.

Objective:To compare the value of 68Ga-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid- D-Phe1-Tyr3-Thr8-octreotide (DOTATATE) and 18F-fluorodeoxyglucose (FDG) PET/CT imaging in the detection of bone metastasis in neuroendocrine neoplasm (NEN). Methods:From January 2014 to July 2019, 29 NEN patients (19 males, 10 females, age: 35-76 years) with bone metastasis who underwent 68Ga-DOTATATE and 18F-FDG PET/CT imaging within one month in Peking University Cancer Hospital & Institute were retrospectively enrolled. Patients were divided into Ki-67≤20% and Ki-67>20% groups according to the tumor proliferation activity, and osteolysis, osteogenesis and no change groups according to the CT findings of bone metastases. The differences of the number and radioactive uptake (maximum standardized uptake value (SUV max) ratio of bone lesion to normal bone (SUV T/B)) of detected bone metastases between 68Ga-DOTATATE and 18F-FDG PET/CT imaging were analyzed. χ2 and Mann-Whitney U tests were used to analyze the data. Results:The sensitivity of 68Ga-DOTATATE and 18F-FDG PET/CT imaging were 75.9%(22/29) and 82.8% (24/29) respectively, and there was no significant difference between the two modalities ( χ2=0.42, P>0.05). The numbers of cases with bone lesions detected by 68Ga-DOTATATE PET/CT imaging in pelvis, spine, ribs, proximal limbs, sternoclavicular scapula and skull were all higher than those of 18F-FDG PET/CT imaging (23, 22, 20, 14, 14, 10 vs 12, 19, 13, 11, 10, 6, respectively). The 68Ga-DOTATATE PET/CT imaging was significantly superior to 18F-FDG imaging in detecting bone metastases (9(3, 36) and 3(0, 18)) and SUV T/B(11.10(3.35, 22.30) and 1.60(1.05, 2.70); U values: 281.000, 77.000, both P<0.001). 68Ga-DOTATATE PET/CT imaging found more bone lesions in well differentiated NEN (Ki-67≤20%) group (11(2, 38) and 2(0, 13)) and osteogenic bone metastasis group (31(3, 100) and 3(0, 31); U values: 105.500, 69.500, both P<0.05). SUV T/B of 68Ga-DOTATATE PET/CT imaging was significantly higher than 18F-FDG PET/CT imaging in all subgroups ( U values: 3.000-22.000, all P<0.05). Conclusion:The 68Ga-DOTATATE PET/CT imaging is superior to 18F-FDG PET/CT imaging in the detection of bone metastasis in NEN.