This exploratory study aims to evaluate the diagnostic, prognostic and response predictive value of a multi biomarker strategy in patients with Gastroenteropancreatic Neuroendocrine Tumors (GEP NETs) originating from the midgut or pancreas. Using a recently developed methodology enabling the evaluation of 92 concomitant cancer biomarkers will provide an interesting approach to solve this question (Lundberg et al 2011).

Inclusion Criteria:

• Provision of written informed consent prior to any study related procedures.
• Suspected of suffering from a metastatic midgut NET or Pancreatic non-functional NET (WHO grade 1 or 2, up to 10% Ki67).
• Male or female aged 18 or older.

Exclusion Criteria:

• Previously treated for the NET disease with pharmaceutical treatment, Peptide Receptor Radionuclide Therapy (PRRT) or radiation therapy(surgery of primary tumour is accepted)
• Has any mental condition rendering the subject unable to understand the nature, scope and possible consequences of the study, and/or evidence of an uncooperative attitude.
• Suffering from a malignant disease or previously treated for a malignant disease within the last 6 months.
• Suffering from a chronic inflammatory disease.
• Suffering from a renal and/or liver disease.

Patients from a specialist clinic with a suspected diagnosis of metastatic GEP NETs and healthy controls matched by age and gender.