Vasoactive intestinal peptide receptor scintigraphy

The high-level expression of VIP receptors on tumor cells provided the basis for the successful use of 123I-labeled VIP for the in vivo localisation of intestinal adenocarcinomas and endocrine tumors. After injection of HPLC-purified 123I-VIP (150-200 MBq / 300 pmol / patient) planar and SPECT acquisitions were performed between 0.5-1 and 2-4 hours (and up to 24 hours) in most patients. Patients with adenocarcinomas were followed until death or for at least 6 months. In a cohort of 60 patients with pancreatic cancer, the primary tumors were visualised in patients (90%) with disease confined to the pancreas and in patients (32%) suffering both from locoregional and disease metastatic to the liver. Liver metastases were imaged in patients (scan sensitivity 90%) and lymph-node metastases in patients. In 5 patients, the VIP receptor scan indicated the malignant lesion prior to CT and led to surgical intervention in 2 patients. A similar high sensitivity rate of the VIP receptor scan was obtained in a cohort of 80 patients with colorectal cancer. In this group, VIP scan results led to a change in the stage of the disease in 7 patients. VIP also localised primary intestinal carcinoids and insulinomas (sensitivity 80%, n=27), but had only low sensitivity rates for other neuroendocrine tumors such as pheochromocytomas, gastrinomas and unclassified APUDomas. In a prospectively randomised study, VIP receptor imaging was superior to antibody targetting of malignant intestinal disease. We conclude that the VIP receptor scintigraphy has the potential to offer additional information to diagnostic standard methods and could influence the decision making process in the treatment of intestinal carcinomas.