[18F]Fluorodeoxyglucose accumulation as a biological marker of hypoxic status but not glucose transport ability in gastric cancer.

BACKGROUND: The use of [18F] 2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) for detection of gastric cancer is often debated because FDG uptake varies for each patient. The purpose of this study was to clarify the molecular mechanisms involved in FDG uptake. MATERIAL AND METHODS: Fifty patients with gastric cancer who underwent FDG-PET and gastrectomy were studied. Snap-frozen tumor specimens were collected and examined by real-time PCR for relationships between maximum standardized uptake value (SUV) and mRNA expression of the following genes: glucose transporter 1 (GLUT1), hexokinase 2 (HK2), hypoxia-inducible factor 1α (HIF1α), and proliferating cell nuclear antigen (PCNA). RESULTS: Tumor size was the only clinicopathological parameter that significantly correlated with SUV. Transcripts for the genes evaluated were about three-fold higher in malignant specimens than in normal mucosa, although only HIF1α was significantly correlated with SUV. When divided into intestinal and non-intestinal tumors, there was a significant correlation between SUV and tumor size in intestinal tumors. Interestingly, the weak association between SUV and HIF1α expression in intestinal tumors was substantially stronger in non-intestinal tumors. No correlation was found between SUV and mRNA expression of other genes in intestinal or non-intestinal tumors. CONCLUSION: SUV was correlated with HIF1α, but not PCNA, HK2, or GLUT1 expression. FDG accumulation could therefore represent tissue hypoxia rather than glucose transport activity for aggressive cancer growth.

Correlation of 18F-FLT uptake with equilibrative nucleoside transporter-1 and thymidine kinase-1 expressions in gastrointestinal cancer.

PURPOSE: We examined equilibrative nucleoside transporter-1 (ENT1) and thymidine kinase-1 (TK1) messenger ribonucleic acid (mRNA) expressions in cancer tissue samples to elucidate the mechanism of 3'-deoxy-3'-F-fluorothymidine (FLT) uptake by positron emission tomography (PET) scan in gastrointestinal cancer. METHODS: A total of 21 patients with newly diagnosed gastrointestinal cancer were examined with FLT PET. Tumor lesions were identified as areas of focally increased uptake, exceeding that of surrounding normal tissue. For semiquantitative analysis, the maximal standardized uptake value (SUV) was calculated. The expressions of ENT1 and TK1 in cancer tissue samples were compared with that of FLT SUV. RESULTS: Of all gastrointestinal cancer lesions only one gastric cancer showed focally increased uptake of FLT PET. The mean (±standard deviation) FLT SUV in gastrointestinal cancer was 5.48±1.87. There was no significant correlation between FLT SUV and ENT1 (P=0.90) mRNA expression. There was a significant correlation between FLT SUV and TK1 mRNA expression (P<0.05). CONCLUSION: Results of this preliminary study indicate that TK1 activity is an important determinant of FLT uptake in gastrointestinal cancer. In this study, it was found that ENT1 activity and FLT uptake were not related.

CT assessment of subtypes of pulmonary emphysema in females.

We performed a retrospective study examining the prevalence and subtypes of pulmonary emphysema (PE) identified by computed tomography (CT) in females. We reviewed the records of 1,687 female subjects who had undergone CT. They were divided into the following 2 age groups:group A (＜50 years) and group B (≥50 years). PE was diagnosed by the presence of low-attenuation areas using visual assessment (grades 0-3) on CT images. Two subtypes of PE were observed:centrilobular emphysema (CLE) and paraseptal emphysema (PSE). PE was divided into the following 3 categories:I (CLE or CLE-predominant);II (CLE and PSE of equal extent);and III (PSE or PSE-predominant). PE was found in 64 of 274 smokers (23.3%) and 54 of 1,413 non-smokers (3.8%). In smoking subjects, when grades 1 and 2 were grouped together as mild PE, the mean age for CT grade 3 (severe PE) was significantly higher than that for mild PE. In group A, category III predominated, whereas category I was more prevalent in group B, in both smoking and non-smoking subjects. A high incidence of PE was found in smoking subjects as compared with non-smoking subjects. PSE predominated in younger subjects, whereas CLE predominated in older subjects.

Comparison of 11C-methionine PET and 18F-FDG PET in patients with primary central nervous system lymphoma.

PURPOSE: 2-deoxy-2-[(18)F]fluoro-D-glucose (FDG) positron emission tomography (PET) has been used as a promising tool to diagnose primary central nervous system (CNS) lymphoma because the tumor shows very high FDG accumulation. Although (11)C-methionine (MET) PET has been reported to be useful for evaluating various brain tumors, the role of MET PET in CNS lymphoma is unclear. We compared the uptake of MET and FDG in patients with CNS lymphoma. PROCEDURES: Thirteen immunocompetent patients with CNS lymphoma were examined. All patients underwent PET with MET (15 min p.i.) and FDG (60 min p.i.). PET results were evaluated by visual and semi-quantitative analysis. For semi-quantitative analysis, the standardized uptake value (SUV) and tumor to contralateral normal brain tissue (T/N) ratio were determined by region-of-interest analysis. RESULTS: For detection of CNS lymphoma, sensitivity of PET using both MET and FDG was 100%. The mean (±SD) value of SUV in the contralateral normal brain tissue using MET (1.43 ± 0.21) was significantly lower than that using FDG (5.58 ± 1.79; p < 0.002). The mean (±SD) value of SUV in the CNS lymphoma using MET (4.27 ± 1.91) was significantly lower than that of FDG (13.94 ± 5.65; p < 0.002). There were no significant differences between mean (±SD) T/N ratios using MET PET (3.00 ± 1.26) and FDG PET (2.74 ± 1.25). CONCLUSION: There was no significant difference between T/N ratios using MET PET and FDG PET, although uptake of MET in CNS lymphoma was significantly lower than that of FDG. MET PET showed as high a sensitivity as FDG PET for the detection of primary lesions in patients with CNS lymphoma.

Detection of colorectal cancer using ¹8F-FLT PET: comparison with ¹8F-FDG PET.

OBJECTIVE: We investigated the feasibility of 3'-deoxy-3'-¹8F-fluorothymidine (FLT) positron emission tomography (PET) for the detection of colorectal cancer, in comparison with 2-deoxy-2-¹8F-fluoro-D-glucose (FDG) PET, and investigated correlation of the two radiotracers used with proliferative activity as indicated by Ki-67 index. METHODS: A total of 26 patients with newly diagnosed colorectal cancer were examined with FLT PET and FDG PET. Tumor lesions were identified as areas of focally increased uptake, exceeding that of surrounding normal tissue. For semiquantitative analysis, the maximal standardized uptake value (SUV) was calculated. RESULTS: In all 26 patients, colorectal cancers were detected by both FLT PET and FDG PET. The mean (± SD) values of FLT SUV in colon cancer (5.4 ± 2.4) and in rectal cancer (5.6 ± 1.3) were significantly lower than the corresponding values of FDG SUV (12.4 ± 6.3 and 12.5 ± 4.7, respectively) (P < 0.003). There was no significant correlation between Ki-67 index and either FLT SUV or FDG SUV. CONCLUSION: Although uptake of FLT was found to be significantly lower than that of FDG, both FLT PET and FDG PET were able to detect colorectal cancers in all 26 patients. Neither of the two radiotracers used was correlated with proliferative activity.

Diagnostic value of kinetic analysis using dynamic 18F-FDG-PET in patients with malignant primary brain tumor.

OBJECTIVE: The purpose of this study was to evaluate the efficacy of quantitative imaging of glucose metabolism with positron emission tomography (PET) using kinetic analysis for differentiating between high-grade glioma and central nervous system (CNS) lymphoma. METHODS: Dynamic fluorine-18-fluorodeoxyglucose (18F-FDG)-PET scans obtained in 20 patients with high-grade glioma (World Health Organization grade III, five lesions; grade IV, 15 lesions) and in 12 patients with CNS lymphoma (16 lesions) were retrospectively reviewed. Applying a three-compartment model, parametric images of K1, k2, k3, and k4 and cerebral metabolic rate of glucose (CMR(Glc)) were obtained. RESULTS: On visual analysis, one grade III glioma lesion showed an increase of K1, k2, and k3 values as observed on their respective images. Four grade IV glioma lesions showed an increase of K1 and k2, 11 of k3, and six of CMR(Glc) on their respective images. Fourteen CNS lymphoma lesions showed an increase of K1, 16 of k3, two of k4, and 14 of CMR(Glc). Both k3 and CMR(Glc) values (mean+/-SD) of CNS lymphoma (0.096+/-0.046 and 77.4+/-37.7, respectively) were significantly higher than those of the normal gray matter (0.059+/-0.015 and 41.3+/-9.3, respectively; P<0.007 and P<0.002, respectively). The k3 value of CNS lymphoma was significantly higher than that of grade III (0.058+/-0.022) and grade IV (0.065+/-0.024) gliomas (P<0.03 and P<0.04, respectively). The CMR(Glc) value of CNS lymphoma was significantly higher than that of grade III (33.8+/-7.8) and grade IV (41.5+/-23.1) gliomas (P<0.001 and P<0.004, respectively). The value of k2 of CNS lymphoma was significantly lower than that of grade IV glioma (P<0.05). CONCLUSION: The direct measurement of the regional rate constants by kinetic analysis might be useful for the delineation of CNS lymphoma and for differential diagnosis of high-grade glioma and CNS lymphoma.

Dual time point FDG PET for evaluation of malignant pleural mesothelioma.

OBJECTIVE: To evaluate whether 2-deoxy-2-18F-fluoro-D-glucose (FDG) positron emission tomography (PET) is more useful in differentiating malignant from benign pleural lesions, and whether delayed FDG PET imaging can improve the diagnostic performance in patients with suspicion of malignant pleural mesothelioma (MPM). METHODS: Thirty-three patients who were suspected of having MPM were examined with FDG PET. PET imaging (whole body) was performed at 60 min (early) post-FDG injection and repeated at 120 min (delayed) after injection only in the thoracic region. We evaluated the FDG uptake visually and semiquantitatively. The semiquantitative analysis using the standardized uptake value (SUV) was determined for both early and delayed images (SUVearly and SUVdelayed, respectively). RESULTS: The final diagnosis was MPM in 17 patients and benign pleural disease in 16 patients. The sensitivity, specificity, and accuracy to detect MPM on both early and delayed PET were all 88%. The mean value of SUVdelayed in MPM was significantly higher than that of SUVearly (P < 0.001). The mean values of SUVearly and SUVdelayed in MPM were significantly higher than the corresponding values in benign pleural disease (P < 0.01, respectively). CONCLUSION: FDG PET seems to be a useful imaging modality for differential diagnosis of MPM. In addition, the diagnostic performance on delayed PET was the same as that on early PET, although SUVdelayed was significantly higher than SUVearly in patients with MPM.

Detection of gastric cancer using 18F-FLT PET: comparison with 18F-FDG PET.

PURPOSE: We prospectively investigated the feasibility of 3'-deoxy-3'-(18)F-fluorothymidine (FLT) positron emission tomography (PET) for the detection of gastric cancer, in comparison with 2-deoxy-2-(18)F-fluoro-D-glucose (FDG) PET, and determined the degree of correlation between the two radiotracers and proliferative activity as indicated by Ki-67 index. METHODS: A total of 21 patients with newly diagnosed advanced gastric cancer were examined with FLT PET and FDG PET. Tumour lesions were identified as areas of focally increased uptake, exceeding that of surrounding normal tissue. For semiquantitative analysis, the maximal standardized uptake value (SUV) was calculated. RESULTS: For detection of advanced gastric cancer, the sensitivities of FLT PET and FDG PET were 95.2% and 95.0%, respectively. The mean (+/-SD) SUV for FLT (7.0 +/- 3.3) was significantly lower than that for FDG (9.4 +/- 6.3 p < 0.05). The mean FLT SUV and FDG SUV in nonintestinal tumours were higher than in intestinal tumours, although the difference was not statistically significant. The mean (+/-SD) FLT SUV in poorly differentiated tumours (8.5 +/- 3.5) was significantly higher than that in well and moderately differentiated tumours (5.3 +/- 2.1; p < 0.04). The mean FDG SUV in poorly differentiated tumours was higher than in well and moderately differentiated tumours, although the difference was not statistically significant. There was no significant correlation between Ki-67 index and either FLT SUV or FDG SUV. CONCLUSION: FLT PET showed as high a sensitivity as FDG PET for the detection of gastric cancer, although uptake of FLT in gastric cancer was significantly lower than that of FDG.

Detection of hepatocellular carcinoma using 11C-choline PET: comparison with 18F-FDG PET.

UNLABELLED: The purpose of this study was to retrospectively investigate the feasibility of 11C-choline PET, compared with 18F-FDG PET, for the detection of hepatocellular carcinoma (HCC). METHODS: A total of 16 HCC lesions in 12 patients were examined with both 11C-choline PET and 18F-FDG PET. Tumor lesions were identified as areas of focally increased uptake, exceeding that of surrounding noncancerous liver tissue. For semiquantitative analysis, the tumor-to-liver (T/L) ratio was calculated by dividing the maximal standardized uptake value (SUV) in HCC lesions by the mean SUV in noncancerous liver tissue. RESULTS: 11C-choline PET showed a slightly higher detection rate than did 18F-FDG PET for detection of HCC (63% vs. 50%, respectively), although this difference was not statistically significant. 11C-choline PET had a better detection rate for moderately differentiated HCC lesions but not for those poorly differentiated (75% vs. 25%, respectively). In contrast, 18F-FDG PET exhibited the opposite behavior, with corresponding detection rates of 42% and 75%, respectively. The mean 11C-choline SUV and T/L ratio in moderately differentiated HCC lesions were higher than those in poorly differentiated HCC lesions. In contrast, the mean 18F-FDG SUV and T/L ratio in poorly differentiated HCC were higher than those in moderately differentiated HCC. These differences, however, were also not statistically significant. CONCLUSION: 11C-choline PET had a better detection rate for moderately differentiated HCC lesions but not for poorly differentiated HCC lesions, whereas 18F-FDG PET produced the opposite result. 11C-choline is a potential tracer to complement 18F-FDG in detection of HCC lesions.