Lymph node staging of gastric cancer using (18)F-FDG PET: a comparison study with CT.

UNLABELLED: This study was performed to compare (18)F-FDG PET with CT for the evaluation of primary tumors and lymph node metastases in gastric cancer.

METHODS: Eighty-one patients (28 women and 53 men; mean age, 56.6 y; age range; 32-82 y) who had undergone radical (n = 74) or palliative (n = 7) gastrectomy and lymph node dissection for the management of gastric cancer were included. Preoperative (18)F-FDG PET and CT were reviewed retrospectively for primary tumors of the stomach and lymph node metastases. Any increased (18)F-FDG uptake exceeding that of the adjacent normal gastric wall was considered positive for the primary tumor. Lymph nodes were classified into 3 groups based on their anatomic sites. Because perigastric lymph nodes (N1) were often not clearly differentiated from primary tumors, N1 lymph node metastases were determined when possible. Lymph nodes were considered positive or negative on the basis of the group as a whole. Final conclusions for primary tumors and lymph node metastases were based on histopathologic specimens in all patients.

RESULTS: There were 17 patients with early gastric cancer (EGC) and 64 patients with advanced gastric cancer (AGC). For primary tumors, both PET and CT showed a sensitivity of 47% (8/17) for EGC and 98% (63/64) for AGC. The sensitivity of CT for N1 disease was significantly higher than that of PET. (18)F-FDG PET had a sensitivity, specificity, and accuracy of 34% (11/32), 96% (47/49), and 72% (58/81), respectively, for N2 metastases, whereas the corresponding CT values were 44% (14/32), 86% (42/49), and 69% (56/81). For N3 metastases, PET and CT had the same sensitivity, specificity, and accuracy: 50% (3/6), 99% (74/75), and 95% (77/81), respectively. Overall, the sensitivity, specificity, and accuracy of (18)F-FDG PET were not significantly different from those of CT for primary tumors or for N2 and N3 metastases.

CONCLUSION: (18)F-FDG PET is as accurate as CT for the detection of primary tumors of either EGC or AGC. The low sensitivities of PET and CT were insufficient to allow decision making on the extent of lymphadenectomy. In contrast, the high specificity of PET for N disease appeared valuable, and the presence of N disease on PET may have a clinically significant impact on the choice of initial therapy.