| BackgroundWith the progress of technology and China’s economic development people’slife and health conditions has been greatly improved. Recent studies indicate thatgastric cancer incidence and mortality increased year by year. The survival and theprognosis of patients with gastric cancer are quite different, which is related to manyfactors, such as age, tumor size and depth of invasion, lymph node metastasis,differentiation and some molecular markers Her-2(human epidermal growth factorreceptor-2, Her-2), VEGF, EGFR(epidermal growth factor receptor, EGFR) and theregional lymph node metastasis is a key factor for the decision of surgical approach.With the advent of PET/CT(positron emission tomography/computed tomography,PET/CT),which improve the accuracy of clinical diagnosis and staging of gastriccancer. PET/CT can obtain a check information on systemic disease, it reflectsmetabolism, nucleic acid synthesis activity of the cell receptor and change the cellnucleus cells at the molecular level, the most commonly used markers are18F-FDG(fluorodeoxyglucose, FDG).18F-FDG reflects glucose metabolism in vivo, and because the metabolism of malignant cells leading to increased demand for glucose,so intravenous glucose analogue-18F-FDG, the majority of tumor lesions aremanifested as high18F-FDG uptake, thus18F-FDG PET/CT imaging for theevaluation of primary gastric cancer size, serosal invasion, lymph node metastasisand distant metastasis has important clinical value, it can be used for gastric cancerTNM staging. But its specificity for tumor diagnosis is poor, inflammation,sarcoidosis, muscle and fat physiological18F-FDG uptake is also increased.18F-FLT (fluorothymidine, FLT) is a fluorine-labeled thymidine, are nucleic acidmetabolism imaging agent, by Na+-dependent transporter protein or passivediffusion go through into the cells, by thymidine kinase (TK-1) phosphate as18F-FLT-phosphate (MP), and18F-FLT-MP5’-nucleotide hydrolysis by intracellulargeneration18F-FLT and transported out of the cell, excreted by kidneys. Theactivity of TK-1is determined by the cell cycle, TK-1in quiescent cells are not active,but when it is in the early G1phase of the cell proliferation increases theactivity,and in the end of S phase and G2phase go to the peak. Rapidlyproliferating tumor cells can increase the activity of TK-1, proliferation of normalcells is three to four times, and thus in S phase of the cell malignancies TK1activityenhancement,18F-FLT uptake reflects the extent of the TK1activity and the TK1activity reflects the level of cell proliferation. Therefore,18F-FLT as thymidinekinase substrate may reflect proliferative status of tumor cells. Tumor cell DNAsynthesis strengthened, and inflammatory cells are mature cells, DNA synthesisactivity is not high, so18F-FLT imaging can be complement for18F-FDG imagingcan not effectively identify deficiencies inflammation and tumors. Several studieshave indicated that18F-FLT PET/CT may reflect tumor proliferation and forevaluation of treatment response. Based on the37patients with gastric cancerthrough biopsy confirmed cases analyzed the clinical value of18F-FLT combined18F-FDG PET/CT imaging for the detection of primary and regional lymph nodesmetastasis.ObjectionTo evaluate the diagnostic value of18F-FLT combined with18F-FDG PET/CTimaging on gastric cancer for local foci and regional lymph nodes metastases. MethodsThirty-seven patients underwent18F-FLT and18F-FDG PET/CT imaging fromMarch2011to April2013. All patients underwent gastrectomy andlymphadenectomy. The images were analyzed by visual and semi-quantitativeanalysis. The diagnostic efficiency of dual-tracer PET/CT was calculated accordingto the postsurgical pathologic findings. Two-sample t-test and χ2test wereperformed using SPSS13.0.Results1. For the primary lesion, the diagnostic sensitivities of18F-FLT PET and18F-FDGwere89.2%(33/37) vs91.9%(34/37), respectively (χ2=0.158, P>0.05). The18F-FLT SUVmax of16patients with nonintestinal tumours was significantlyhigher than that of21patients with intestinal tumours (6.89±1.38vs3.79±2.45, t=4.533, P<0.05); While the18F-FDG SUVmax was not significantlydifferent between the2groups of patients (7.13±1.97vs6.36±2.32, t=1.066,P>0.05).2. For detecting metastatic regional lymph nodes, the diagnostic sensitivity,specificity and accuracy of18F-FLT and18F-FDG were64.8％(35/54) vs88.9％(48/54),97.6％(246/252) vs82.9％(209/252)，91.8％(281/306) vs84.0％(257/306), respectively (χ2=8.796,30.948,8.854, all P<0.05). Thecombination of dual-tracer PET/CT improved the sensitivity, specificity andaccuracy up to92.6%(50/54),98.8%(249/252), and97.7%(299/306).Conclusions18F-FLT may represent a superior radiotracer for visualization of gastric cancerwith low or no18F-FDG uptake. Compared with18F-FDG PET/CT，18F-FLT PET/CTmay be less sensitive but more specific and accurate for the metastatic regionallymph nodes. Dual-tracer PET/CT using18F-FDG and18F-FLT could improve thediagnostic accuracy of metastatic regional lymph nodes. |
PDF Full Text Request