Chromogranin A as Blood Marker in Cancer Patients

A general characteristic for neuroendocrine tumors (NET) is expression of chromogranin A (CgA), which is released from neuroendocrine cells, occasionally together with cell specific hormones such as gastrin, insulin, somatostatin, and serotonin in functional tumors. Human CgA is an acidic 439 amino acid protein with a sequence containing several mono- and dibasic cleavage sites, and correspondingly, numerous fragments of CgA have been identified in tissue and plasma. CgA is critical to the formation of secretory granules that characterize NETs, and is therefore a useful marker for NETs. Plasma concentrations of CgA and/or CgA fragments are elevated in most NETs. Moreover, since plasma CgA concentrations seem to be closely related to tumor burden in humans, plasma CgA concentration is an important prognostic factor. As such, high plasma concentrations of CgA as well as a dramatic increase in plasma CgA within a short time period, is associated with a poorer prognosis. Plasma CgA has also been suggested to be useful in the follow-up of patients with NETs. Taken together, these observations support the notion that CgA is a promising biomarker candidate for monitoring treatment effectiveness and disease progression or regression. Participation in this clinical study requires no additional visits to the oncologist, radiology or the laboratory. All information needed for the study will be obtained during typical visits as recommended by the oncologist. Clinical assessment of patients with GEP-NETs (according to NCCN guidelines) is based on physical exam, imaging (CT or MRI scans) and laboratory parameters. The course of disease is followed by RECIST 1.1 categorization including the evaluation of tumor burden by imaging.