Peptide Receptor Radionuclide Therapy With 177Lu-Dotatate Associated With Metronomic Capecitabine In Patients Affected By Aggressive Gastro-Etero-Pancreatic Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are relatively rare tumors, mainly originating from the digestive system, able to produce bioactive amines and hormones. NETs tend to be slow growing and are often diagnosed when metastatic. Treatment is multidisciplinary and should be individualized according to the tumor type, burden, and symptoms. Therapeutic tools include surgery, interventional radiology, and medical treatments such as somatostatin analogues, interferon, chemotherapy, new targeted drugs (everolimus, sunitinib) with radiolabelled somatostatin analogues. Despite the options available, antiproliferative treatment options for patients with inoperable gastro-entero-pancreatic (GEP) NETs are limited.

PRRT with radiolabelled somatostatin analogues 90Y-DOTATOC, and 177Lu-DOTATATE (177Lu-DOTA-D-Phe1-Tyr3-octreotate), has been experimented for more then 15 years in few centers. The introduction of PRRT and, particularly, the advent of 177Lu-DOTATATE, broke through the poor scenario of available treatment for NETs.

Dosimetric studies demonstrated that 90Y-DOTATOC and 177Lu-DOTATATE are able to deliver high radiation doses to somatostatin receptor sst2-expressing tumors and low doses to normal organs. Clinical studies demonstrated that partial and complete objective responses in up to 30% of patients can be obtained, with a great survival benefit including those with stable disease. Side effects may involve the kidney and the bone marrow and are usually mild. Renal protection is used to minimize the risk of a late decrease of renal function.

Recently, in order to further increase the objective response to PRRT, a combined treatment with the radiosensitizer capecitabine, has been proposed and tested on GEP-NET patients' population. Capecitabine is the oral prodrug of 5-fluorouracile (5-FU), which is active in GEP tumors and a radiosensitizer itself. The finding that neo-angiogenesis can be shut down also with cytotoxic drugs like capecitabine when administered in low and frequent doses, constitutes the rationale for proposing a particular schedule of chemotherapy that is, therefore, named "metronomic" or "anti-angiogenic".

Based on the reported experience, the investigators think to offer a combined therapy in aggressive, metabolically active tumors, such as those patients with a positive FDG scan. FDG-PET allow the investigators to obtain in vivo imaging of increased glycolysis which is known to be an hallmark of tumor aggressiveness.