Analysis of tumor uptake of Iod-123-Methyltyrosine in fused PET-MRI in a mouse xenotransplantation model of pancreatic cancer

Objectives In pancreatic cancer imaging with F-18-FDG-PET has shown to be usefull, however its not available just anywhere. Therefore substitution with a more commonly used tracer like Iod-123-Methyltyrosine (I-123-IMT) would be helpful for imaging of pancreatic cancer .The aim of the underlying study was to examine its uptake in an animal modell.

Methods A celline of pancreatic cancer (PancTull) was transplanted orthotopically and subcutaneously respectively in eight SCID-beige-mice which received 15 MBq of I-123-IMT for imaging. Two hours after injection combined imaging was performed with micro-SPECT and a 3T MR scanner using a dedicated mouse coil. Tumor uptake analysis was based on ROI interpretation using a Tumor/Background ratio (T/B) with the adjacent visceral region as background.

Results In all of the eight mice a significantly higher uptake into tumor tissue could be elicited. After subcutaneous xenotransplantation the T/B was 10,25 (2,9-17,9) and after orthotopic xenotransplantation it was 11,15 (2,5-27,3). Fusion with MRI enabled good correlation of the anatomical site of the tumor with I-123-IMT uptake.

Conclusions From experiments with glioma cells it is well known that the uptake of IMT depends on an acid-anionic-transporter (LAT1) and that I-123-IMT is not incorporated into the proteins. Therefore we conclude that this specific transporter, LAT 1 is present in the underlying model of pancreatic cancer leading to the significantly higher tumor uptake. In this case the use of I-123-IMT could be considered as an economical alternative to FDG-PET in pancreatic carcinoma.