Positronenemissionstomographie neuroendokriner Tumoren: Etablierung eines Mausmodells und Biodistribution ausgewählter PET-Tracer

Neuroendocrine tumors are a heterogeneous group of relatively rare malignancies. The value of FDG positron emission tomography for the assessment of neuroendocrine tumors is limited. Preliminary studies indicate that 18F-DOPA and various somatostatin analogs such as 68Ga-Dotanoc are more accurate for disease assessment. Moreover 68Ga-labelled somatostatin analogs provide additional data on receptor status that are crucial for targeted radionuclide therapy. The purpose of this study was to determine, using microPET, the diagnostic accuracy of FDG, 18F-DOPA and 68Ga and 111In labelled somatostatin analogs for detecting human gastroenteropancreatic neuroendocrine tumors and medullary thyroid carcinoma in a mouse model and to define time points providing maximum information. Human tumor cells were implanted subcutaneously into SCID mice. 39 animals received human gastroenteropancreatic neuroendocrine tumor cells, 25 animals medullary thyroid carcinoma cells. 4 to 6 weeks after tumor injection, microPET scanning was performed to determine the tracer uptake in tumors and normal tissues. PET images were acquired continuously directly after tracer application. Animals were sacrificed at various time points post-injection for quantitative radiotracer biodistribution studies. For gastroenteropancreatic neuroendocrine tumors tumor/organ uptake ratios were highest for FDG and lowest for somatostatin analogs. Within the somatostatin analogs 111In-Dotanoc showed a slightly superior result compared to Dotatoc and Dotasom. For medullary thyroid carcinomas tumor/organ uptake ratios were highest for 68Ga-Dotatoc and lowest for FDG. This is consistent with the results of preliminary studies. For all substances, comparing time points, relative peak uptake was highest at 120 minutes post-injection. Furthermore there was no significant difference between somatostatin analogs labelled with 68Ga or 111In