Evaluation of 18 F-FDG uptake for detecting lymph node metastasis of gastric cancer: a prospective pilot study for one-to-one comparison of radiation dose and pathological findings

Background Gastric cancer exhibits various degrees of fluorine F-18 fluorodeoxyglucose ( 18 F-FDG) uptake on positron emission tomography/computed tomography (PET/CT). We evaluated the relationship between 18 F-FDG uptake and the presence/absence of metastasis in individual lymph nodes (LN) on a one-to-one basis. Methods We analyzed 21 patients with gastric cancer. We injected 18 F-FDG intravenously in the morning, and gastrectomy with LN dissection was performed in the afternoon of the same day. Radiation doses were measured at each LN using a well-type counter, and we then compared 18 F-FDG uptake, the shortest diameter, and pathological examination results for each LN. Results In our study, 906 LNs were analyzed, including 115 metastatic LNs. Metastatic LNs showed significantly higher 18 F-FDG uptake ( P < 0.0001), and were significantly enlarged ( P < 0.0001). The receiver operating characteristics (ROC) curve had a larger area under the curve (0.71) for 18 F-FDG uptake than for the shortest LN diameter (0.60). Considering histology, the ROC curve for intestinal type adenocarcinoma had a larger area under the curve than that for diffuse type (0.75 vs 0.61). Conclusions F-FDG uptake is potentially a more useful variable than LN diameter for discriminating between LN with and without metastasis, especially in intestinal type gastric cancer cases.