Personalized CAPTEM Radiopeptide Therapy of Advanced, Non-resectable Neuroendocrine Cancer

This is a non-randomized, phase II, open label study. The purpose of this study is to: • estimate Progression Free Survival (PFS) after treatment with Peptide Receptor Radionuclide Therapy (PRRT) 177Lu-DOTATOC standard dose (up to 4x7,4GBq 177Lu DOTATOC) in combination with capecitabine (CAP) and temozolomide (TEM) - CAPTEM. Patients with advanced, non-resectable and/or progressive gastro-entero-pancreatic neuroendocrine tumors, GEP-NET according to WHO 2017 classification, (histological grade G1, G2), in selected cases patients with high proliferation index (Ki-67\> 20%, usually below 55%), NETG3 - pancreatic, midgut neuroendocrine tumors and carcinoma of unknown primary (CUP). All with overexpression of somatostatin receptor (SSTR positive) based on somatostin receptor scintigraphy (SRS), will be enrolled in this study. * evaluate the safety and tolerability of combination therapy using 177Lu-DOTATOC and CAPTEM. * evaluate the health related quality of life (QoL) as measured by the European Organization for Research and Treatment of Cancer (EORTC) QLQ-G.I.NET21 questionnaire. * evaluate internal dosimetry, in a subset up to 20 patients, but at least 10 patients. * explore the correlation of clinical efficacy outcomes with Somatostatin Receptor Scintigraphy (SRS) using 99mTc HYNICTOC (Tektordyt®) tumour uptake score. * explore the correlation of clinical efficacy outcomes with the levels of some specific and non-specific biomarkers and gene transcripts analysis. * compare the Time to Tumour Progression (TTP). The schedule of treatment will include 4 courses; capecitabine (CAP), which will be administrated for 14 days with 8-week breaks, combined at 10th day with 177Lu-DOTATOC (PRRT - Peptide Receptor Radionuclide Therapy) in doses from 5,55GBq up to 7,4 GBq administered i.v. up to four times in every patient during whole therapy. In selected patients, in those with only liver involvement or dominant liver bulky disease third and fourth administration of PRRT will be used intra-arterial administration (i.a.) via hepatic artery. The administered dose will be from 2.85 GBq up to 3.7GBq, up to two times per whole therapy, followed in each case of i.v. or i.a. PRRT by Temozolomide (TEM) p.o. administration, which will be given during 10-14th days in each therapy sessions. Doses of PRRT could be modified due to clinical stage and laboratory parameters. Treatment will be discontinued in the case of a cumulative dose 29,6 GBq, corresponding to the radiation dose on the bone marrow below 2 Gy and cumulative dose on kidney below 23 Gy. In case of radiation dose on kidney above 23 Gy treatment will be interrupted.