Localisation and staging of gastrin producing tumours using cross-sectional imaging modalities

Cross sectional imaging in the assessment of gastrinomas has three major applications: Tumor localization (sporadic gastrinoma, MEN I) in patients undergoing primary or secondary surgery. Staging of metastasized tumors, especially assessment of lymph nodes and liver metastases, possibly including a risk analysis prior to liver resection. Post-surgery follow-up and monitoring of bio- or chemotherapy. Detection of primary tumors is strongly correlated with their size. However, the sensitivity of surgical assessment of the mostly small tumors by experienced surgeons is much higher than that of any imaging modality. Of all imaging modalities, endoultrasonography (EUS) followed by Somatostatin receptor scintigraphy (SRS) is the most sensitive modality for the assessment of pancreatic tumors in asymptomatic patients suffering from a MEN-I syndrome. Scintigraphy has the highest sensitivity in tumors of symptomatic patients and in the assessment of metastases. CT and MRI are only second line diagnostic modalities. Their sensitivity is largely dependent on the selection of patients. As a potential application, 3D reconstruction of nearly isotropic CT data sets for the risk assessment prior to liver resection is currently developing. Due to the absent radiation exposure, MRI is increasingly utilized to monitor the response of metastases under systemic therapy, e.g. in clinical trials.