Comparison of Positron Emission Tomography Using 2-[^18F]-fluoro-2-deoxy-D-glucose and 3-deoxy-3-[^18F]-fluorothymidine in Lung Cancer Imaging

Background： The detection of solitary pulmonary nodules （SPNs） that may potentially develop into a malignant lesion is essential for early clinical interventions. However, grading classification based on computed tomography （CT） imaging results remains a significant challenge. The 2-[^18F]-fluoro-2-deoxy-D-glucose （^18F-FDG） positron emission tomography （PET）/CT imaging produces both false-positive and false-negative findings for the diagnosis of SPNs. In this study, we compared 18F-FDG and 3-deoxy-3-[^18F]-fluorothymidine （^18F-FLT） in lung cancer PET/CT imaging. Methods： The binding ratios of the two tracers to A549 lung cancer cells were calculated. The mouse lung cancer model was established （n = 12）, and micro-PET/CT analysis using the two tracers was performed. Images using the two tracers were collected from 55 lung cancer patients with SPNs. The correlation among the cell-tracer binding ratios, standardized uptake values （SUVs）, and Ki-67 proliferation marker expression were investigated. Results： The cell-tracer binding ratio for the A549 cells using the ^18F-FDG was greater than the ratio using 18F-FLT （P 〈 0.05）. The Ki-67 expression showed a significant positive correlation with the ^18F-FLT binding ratio （r = 0.824, P〈 0.01）. The tumor-to-nontumor uptake ratio of ^18F-FDG imaging in xenografts was higher than that of ^18F-FLT imaging. The diagnostic sensitivity, specificity, and the accuracy of ^18F-FDG for lung cancer were 89%, 67%, and 73%, respectively. Moreover, the diagnostic sensitivity, specificity, and the accuracy of ^18F-FLT for lung cancer were 71%, 79%, and 76%, respectively. There was an obvious positive correlation between the lung cancer Ki-67 expression and the mean maximum SUV of ^18F-FDG and ^18F-FLT （r = 0.658, P〈 0.05 and r = 0.724, P〈 0.01, respectively）. Conclusions： The ^18F-FDG uptake ratio is higher than that of ^18F-FLT in A549 cells at the cellular level.^18F-FLT imaging might be superior for the quantitative diagnosis of lung tumor tissue and could distinguish lung cancer nodules from other SPNs.

Significant value of 18F-FDG-PET/CT in diagnosing small cervical lymph node metastases in patients with nasopharyngeal carcinoma treated with intensity-modulated radiotherapy

Background: Little is known about the nature of metaistasis to small cervical lymph nodes(SCLNS) in the patients with nasopharyngeal carcinoma(NPC)examined by using 18-fluoro-2-deoxy-glucose(^(18)F-FDG) positron emission tomography/computed tomography(PET/CT).The present study aimed to evaluate the diagnostic values of PET/CT in identifying metastasis in SCLNs in NPC patients.Methods: Magnetic resonance images(MRI) and PET/CT scans for 470 patients with newly diagnosed, non-distant metastatic NPC were analyzed. Metastatic rates of SCLNs were defined by the positive number of SCLNs on PET/CT scans and total number of SCLNs on MRI scans. Receiver operating characteristic curve was applied to compare PET/CT-determined stage with MRI-determined stage.Results: In total, 2082 SCLNs were identified, with 808(38.8%) ≥ 5 and < 6 mm in diameter(group A), 526(25.3%)≥ 6 and < 7 mm in diameter(group B),374(18.0%)≥ 7 and < 8 mm in diameter(group C), 237(11.4%) ≥8 and<9 mm in diameter(group D),and 137(6.5%) ≥ 9 and <10 mm in diameter(group E).The overall metastatic rates examined by using PET/CT for groups A, B,C,D, and E were 3.5%, 8.0%, 31.3%, 60.0%, and 83.9%, respectively(P< 0.001). In level IV/Vb, the metastatic rate for nodes ≥ 8 mm was 84.6%. PET/CT examination resulted in modification of N category and overall stage for 135(28.7%) and 46(9.8%) patients, respectively. The areas under curve of MRIdetermined and PET/CT-determined overall stage were 0.659 and 0.704 for predicting overall survival, 0.661 and 0.711 for predicting distant metastasis-free survival, and 0.636 and 0.663 for predicting disease-free survival.Conclusions: PET/CT was more effective than MRI in identifying metastatic SCLNs, and the radiologic diagnostic criteria for metastatic lymph nodes in level IV/Vb should be re-defined.

Malignant Triton Tumor in the Abdominal Wall: A Case Report

Malignant triton tumor (MTT) is a rare variant of malignant peripheral nerve sheath tumor (MPNST) with rhabdomyosarcomatous differentiation. We report the case of a 54-year-old male without a history of neurofibromatosis type 1 (NF1) who had a growing abdominal wall tumor diagnosed as MTT. Computed tomography (CT), magnetic resonance imaging (MRI) and 2-[F-18]-fluoro-2-deoxy-D-glucose positron emission tomography/CT (FDG-PET/CT) were performed. The MRI and FDG-PET/CT indicated that the lateral component of the tumor was composed of many proliferative cells, corresponding to the histopathological finding of a cellular proliferation of spindle-shaped cells. In light of this case and previous reports, it is apparent that FDG-PET/CT is a helpful tool for distinguishing MTT from benign peripheral nerve sheath tumor.