Endocrine Abstracts

Introduction: Neuroendocrine tumors (NET) are heterogenous tumors with variable survival and the frequently occurring ability to metastasize. A basis for metastasis of tumors is invasive growth. One factor participating in this process is the existence of the so called ‘circulating tumor cells’ (CTC) in the peripheral blood. Up to now there is only rare data available regarding the number of CTCs in NET patients.

Methods: EpCAM protein expression was evaluated in cancer cell lines as well as NET patients. NET patients’ peripheral blood mononuclear cells (PBMCs) were investigated by immunohistochemical staining, defining CTCs to be CD45 negative and EpCAM positive. Up to now 14 NET patients were included into the ongoing study (six females, mean age: 48 years (range, 25–80 years); eight males, mean age: 64 years (range, 54–77 years)). The following NETs were included: five pancreatic tumors, three bronchopulmonary tumors, two pheochromocytomas, and four tumors with unknown primary. Eight patients showed morphological detectable metastatic spread (57%).

Results: Analyses of a medullary thyroid carcinoma cell line (TT-cells) showed a stronger EpCAM expression compared to a leukemia cell line (K 562 cells). CTC analyses of NET patient revealed CTC existence within the peripheral blood of 3 (21%) NET-patients (mean number of CTCs: 5/7.5 ml blood). This was the case in one pancreas NET patient, one pheochromocytoma patient, and in one NET patient with CUP (cancer of unknown primary) syndrome. All three patients showed metastatic spread. Correlation analyses between CTC levels and serum chromogranin A levels as well as disease progression are ongoing.

Conclusion: This study underlines the previously described EpCAM expression of NET-cells. Our systematic analysis indicates a correlation between the presence of CTC within the peripheral blood and metastatic spread. Further investigation is needed to underline our results. This study is ongoing.