ABSTRACT:

To assess the role of 3'-deoxy-3'-18F-fluoro-thymidine (18F-FLT) and 2'-deoxy-2'-18F-fluorodeoxy-glucose (18F-FDG)  positron emission tomography (PET) imaging in the evaluation of the therapeutic effects of radiotherapy during treatment of lung adenocarcinoma. Eighteen mice with lung adenocarcinoma were randomly divided into 2 groups; each group was randomly paired and evenly divided into three smaller groups, namely, A, B and C. Group A served as the control group without any treatment; mice in group B were received radiotherapy in sites of tumor. A single dose of 2000 cGy, 6MV x-ray was used in this experiment; mice in group C also received radiotherapy at sites of tumors two days before the experiment using the same procedure and dose as group B. Micro PET imaging was taken after intravenous injection of 18F-FLT and 18F-FDG through the mice’s tail. The intake ratio of 18F-FLT and 18F-FDG was much higher at the tumor sites. After radiotherapy, 18F-FLT uptake was significantly lower than that of the control group (p < 0.05), while there was no obvious change of 18F-FDG uptake. There was a significant decrease in T/NT value of FLT PET imaging group 24 and 48 h after radiotherapy; a significant difference could be seen, compared with that before radiotherapy (p < 0.05). Change in 18F-FLT uptake induced by radiotherapy is more sensitive than that of 18F-FDG. Intake of 18F-FLT is lowered more significantly after radiotherapy than that of 18F-FDG, and this can serve as evidence that 18F-FLT is an effective tracer to monitor the therapeutic effect of radiotherapy on malignant tumors.