A pilot study of the diagnostic and prognostic values of FLT-PET/CT for pancreatic cancer: comparison with FDG-PET/CT.

PURPOSE: The purpose of the study was to examine the diagnostic and prognostic values of 18F-fluorothymidine (FLT)-PET/CT for pancreatic cancer by comparing with 18F-fluorodeoxyglucose (FDG)-PET/CT. METHODS: Fifteen patients with newly diagnosed pancreatic cancer underwent both FLT and FDG-PET/CT scans before treatment. The sensitivity, specificity, and accuracy in detecting nodal and distant metastases were compared between both scans using McNemar exact or χ 2 test. Progression-free survival (PFS) and overall survival (OS) were calculated by Kaplan-Meier method. Prognostic significance was assessed by Cox proportional hazards analysis. RESULTS: Both scans visualized all primary cancers. The sensitivity, specificity, and accuracy per patient basis for detecting nodal metastasis were equal and 63.6% (7/11), 100% (4/4), and 73.3% (11/15) for both scans, and for detecting distant metastasis were 100% (6/6), 88.9% (8/9), and 93.3% (14/15) for FDG-PET/CT, and 50.0% (3/6), 100% (9/9), and 80.0% (12/15) for FLT-PET/CT, respectively, without significant difference in each of them between both scans (p > 0.05). However, of 4 patients with multiple liver metastases, FDG-PET/CT was positive in all, but FLT-PET/CT was negative in three patients. At univariate analysis, only FLT-SUVmax correlated with PFS (hazard ratio, 1.306, p = 0.048), and FDG total lesion glycolysis (TLG), FLT-SUVmax, and FLT-total lesion proliferation (TLP) correlated with OS (p = 0.021, p = 0.005, and p = 0.022, respectively). At bivariate analysis, FLT-SUVmax was superior to FDG-TLG or FLT-TLP for prediction of OS [HR (adjusted for FDG-TLG), 1.491, p = 0.034, HR (adjusted for FLT-TLP), 1.542, p = 0.023]. CONCLUSION: FLT-PET/CT may have a potential equivalent to FDG-PET/CT for detecting primary and metastatic cancers except liver metastasis. FLT-SUVmax can provide the most significant prognostic information.

Current clinical status of 18F-FLT PET or PET/CT in digestive and abdominal organ oncology.

Positron emission tomography (PET) or PET/computed tomography (CT) using 18F-3'-fluoro-3'-deoxythymidine (18F-FLT) offers noninvasive assessment of cell proliferation in human cancers in vivo. The present review discusses the current status on clinical applications of 18F-FLT-PET (or PET/CT) in digestive and abdominal oncology by comparing with 18F-fluorodeoxyglucose (18F-FDG)-PET (or PET/CT). The results of this review show that although 18F-FLT uptake is lower in most cases of digestive and abdominal malignancies compared with 18F-FDG uptake, 18F-FLT-PET can be used to detect primary tumors. 18F-FLT-PET has shown greater specificity for N staging than 18F-FDG-PET which can show false-positive uptake in areas of inflammation. However, because of the high background uptake in the liver and bone marrow, it has a limited role of assessing liver and bone metastases. Instead, 18F-FLT-PET will be a powerful tool for monitoring response to treatment and provide prognostic information in digestive and abdominal oncology.

Diagnostic performance of ¹8F-fluorothymidine PET/CT for primary colorectal cancer and its lymph node metastasis: comparison with ¹8F-fluorodeoxyglucose PET/CT.

PURPOSE: To examine the diagnostic performance of (18)F-fluorothymidine (FLT) PET/CT in primary and metastatic lymph node colorectal cancer foci in comparison with (18)F-fluorodeoxyglucose (FDG) PET/CT. METHODS: The study population comprised 28 patients with 30 newly diagnosed colorectal cancers who underwent surgical resection of the primary lesion and regional lymph nodes after both FLT and FDG PET/CT. The associations between SUVmax levels and pathological factors were evaluated using the Mann-Whitney U or Kruskal-Wallis test. Differences in diagnostic indexes for detecting nodal metastasis between the two tracers were estimated using the McNemar exact or χ(2) test. RESULTS: All 30 primary cancers (43.0 ± 20.0 mm, range 14 - 85 mm) were visualized by both tracers, but none of the FLT SUVmax values exceeded the FDG SUVmax values in any of the primary cancers (6.6 ± 2.4 vs. 13.6 ± 5.8, p < 0.001). The sensitivity, specificity and accuracy for detecting nodal metastasis were 41% (15/37), 98.8% (493/499) and 94.8% (508/536) for FDG PET/CT, and 32% (12/37), 98.8% (493/499) and 94.2% (505/536) for FLT PET/CT, respectively. The sensitivity (p = 0.45), specificity (p = 0.68) and accuracy (p = 0.58) were not different between the tracers. Nodal uptake of FLT and FDG was discordant in 7 (19%) of 37 metastatic nodes. There were ten concordant true-positive nodes of which six showed higher FDG SUVmax and four showed higher FLT SUVmax, but the difference between FDG and FLT SUVmax was not significant (5.56 ± 3.55 and 3.62 ± 1.45, respectively; p = 0.22). CONCLUSION: FLT has the same potential as FDG in PET/CT for the diagnosis of primary and nodal foci of colorectal cancer despite significantly lower FLT uptake in primary foci.

Clinical significance of primary lesion FDG uptake for choice between oesophagectomy and endoscopic submucosal dissection for resectable oesophageal squamous cell carcinomas.

OBJECTIVES: To correlate primary oesophageal squamous cell carcinoma (SCC) (18)F-fluoro-deoxyglucose (FDG) uptake with pathological factors and examine its significance regarding choice of therapy. METHODS: We retrospectively examined the factors affecting visible and non-visible FDG uptake in 37 primary lesions in 32 oesophageal SCC patients who underwent PET/CT before oesophagectomy or endoscopic submucosal dissection (ESD). We divided the lesions into pathological depth invasion ≥sm2 oesophagectomy (n = 18) and ≤sm1 ESD (n = 19) indicated groups and compared the diagnostic accuracy of FDG-PET with that of endoscopic ultrasound (EUS) performed for 23 superficial lesions to discriminate between these groups. RESULTS: There were 17 visible and 20 non-visible lesions. The lesion visibility was significantly higher in the larger (≥40 mm), non-flat type, more deeply invaded, positive vascular invasion (P < 0.001 each), positive nodal metastasis (P = 0.04) and higher Glut-1 score (P = 0.005) tumour groups. When the visible and non-visible lesions indicated a need for oesophagectomy and ESD respectively, the sensitivity, specificity and accuracy of oesophagectomy were 94% (17/18), 100% (19/19) and 97% (36/37) and those of EUS were 75% (3/4), 79% (15/19) and 78% (18/23) respectively. CONCLUSIONS: Primary lesion FDG visibility can be one of the indicators for choosing between oesophagectomy and ESD for resectable oesophageal SCCs.