Usefulness of gastric water distension and affecting factors to detect measurable disease in advanced gastric cancer on FDG PET-CT

Objectives Ingestion of water enhances the distension of gastric wall, so it can help to evaluate the gastric lesions. As the treatment modalities improve, it seems more important to detect the measurable disease, especially in patients with advanced gastric cancer (AGC). The purpose of this study was to evaluate the usefulness of pre-scanning gastric distension to detect the primary gastric tumor and factors related to detect the measurable disease in AGC.

Methods Fifty-seven patients diagnosed as gastric cancer underwent gastrofiberscopy and FDG PET-CT before treatment. The location, morphology, cell type and differentiation of tumors were determined through gastrofiberscopy and pathology. FDG PET-CT was performed after patients drank 500 ml of water. We regarded the hypermetabolic lesions of which maximum SUV (maxSUV) was higher than “1.35*maxSUV of liver + 2*SD of liver SUV" as a measurable disease. And then, we evaluated what factors from gastrofiberscopic and pathologic findings were related to detect measurable diseases on FDG PET-CT.

Results Among 57 patients (AGC; 39, EGC; 18), primary tumors were visualized in 82% of AGC and 56% of EGC. Measurable diseases on FDG PET-CT were detected in 51% of AGC, using the diagnostic criteria, as we defined in Method Section. Tumors without signet ring cell features on pathology were more detected significantly as a measurable disease than those with signet ring cells (p<0.005). The other factors, such as tumor location, gross morphology, histologic cell type and differentiation of tumors, were not considered as affecting factors to detect measurable diseases.

Conclusions Gastric distension using ingestion of water at pre-scan, helped to visualize gastric tumors on FDG PET-CT. As a view point in detection of a measurable disease, this simple method improved the diagnostic ability in advanced gastric cancer, in spite of their location, morphology, or histology. The only one factor affecting the detectability of measurable diseases was the pathologic findings of signet ring cell features