18F-fluorodeoxyglucose positron emission tomography in the diagnosis of small pancreatic cancer

AIM: To investigate the role of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in the diagnosis of small pancreatic cancer. METHODS: This study involved 31 patients with proven invasive ductal cancer of the pancreas. The patients were divided into 3 groups according to the maximum diameter of the tumor: TS1 (maximum tumor size ≤ 2.0 cm), TS2 (> 2.0 cm and ≤ 4.0 cm) or TS3-4 (> 4.0 cm). The relationships between the TS and various diagnostic tools, including FDG-PET with dual time point evaluation, were analyzed. RESULTS: The tumors ranged from 1.3 to 11.0 cm in diameter. Thirty of the 31 patients (97%) had a positive FDG-PET study. There were 5 patients classified as TS1, 15 as TS2 and 11 as TS3-4. The sensitivity of FDG-PET, computed tomography (CT) and magnetic resonance imaging (MRI) were 100%, 40%, 0% in TS1, 93%, 93%, 89% in TS2 and 100%, 100%, 100% in TS3-4. The sensitivity of FDG-PET was significantly higher in comparison to CT and MRI in patients with TS1 (P < 0.032). The mean standardized uptake values (SUVs) did not show a significant difference in relation to the TS (TS1: 5.8 ± 4.5, TS2: 5.7 ± 2.2, TS3-4: 8.2 ± 3.9), respectively. All the TS1 tumors (from 13 to 20 mm) showed higher SUVs in FDG-PET with dual time point evaluation in the delayed phase compared with the early phase, which suggested the lesions were malignant. CONCLUSION: These results indicate that FDG-PET with dual time point evaluation is a useful modality for the detection of small pancreatic cancers with a diameter of less than 20 mm.