CGA and neoplasm: To the best of our knowledge, this is the first study investigating the association between baseline CgA and 5HIAA, as well as their change during treatment, in a uniform cohort of patients with G2 tumours of the small intestine, treated with somatostatin analogues (SSA), peptide receptor radionuclide therapy (PRRT) and/or interferon-alpha (IFN).