Gastric cancer: A 3D PET/CT study with C-11 methionine

Objectives FDG PET/CT has a limited capability of diagnosing gastric cancer. We examined the detectability of gastric cancer with PET/CT using C-11 methionine (MET).

Methods We conducted nine patients who met the following criteria: (1) had advanced gastric cancer confirmed histopathologically; (2) age 20 years old or older; (3) obtained a written informed consent. After 4 hours of fasting, the patients received an intravenous injection of MET (approximately 3.7MBq/kg). The patients were asked to take water to drink just before MET PET/CT scan. Whole body MET PET/CT images from parietal to upper thigh were obtained for approximately 30 min, beginning 20 min after the MET injection. MET PET/CT images were compared with the contrast-enhanced CT (CECT) images examined within 1 week before or after PET/CT. This study was approved by the institutional ethics committee.

Results In 8 of 9 cases, abnormal MET accumulation on PET/CT was detected corresponding to the primary tumor and the lymph node metastases. The SUVmax ranged from 2 to 12. It was difficult to identify detailed border of primary gastric cancer and lymph node metastases nearby due to physiological MET accumulation to normal stomach wall, pancreas and liver. The abnormal MET accumulations of remote lymph node metastases were able to detect easily. The large lesions (2.5cm diameter or more) among multiple liver metastases on CECT showed decreased MET uptake on PET/CT. In one case with negative findings on CECT, abnormal accumulation to the primary tumor was not detected on MET PET/CT.

Conclusions There is a limitation of MET PET/CT for diagnosing gastric cancer due to physiological accumulation of MET to normal stomach wall, liver and pancreas