Role of positron emission tomography scanning in evaluating gastrointestinal neoplasms

Positron Emission Tomography (PET) is rapidly evolving into a useful imaging modality for early and accurate detection of malignant tumor sites. Several recent studies have documented improved efficacy of detecting recurrent colorectal and hepatic (primary and metastatic) tumor sites with a sensitivity ranging from 92% to 100% and an accuracy of 90% to 96%. PET-FDG imaging using 2-[18F]-fluoro-2-deoxy-D-glucose has been found to be superior to computed tomography (CT) in detecting recurrent colorectal, hepatic, and abdominopelvic recurrent tumor sites from different primary cancers. PET-FDG imaging can be a cost-effective tool in the screening of patients with an elevated carcinoembryonic antigen and/or equivocal CT findings and suspected colorectal cancer. The role of PET scanning using FDG or C-11-5-HTP or C-11-L-DOPA appears promising in pancreatic carcinoma and functional endocrine tumors. Further studies are being carried out to assess the role of PET scanning in other gastrointestinal cancers.