Long-Term Survival and Value of (18)F-FDG PET/CT in Patients with Gastroenteropancreatic Neuroendocrine Tumors Treated with Second Peptide Receptor Radionuclide Therapy Course with (177)Lu-DOTATATE

Peptide receptor radionuclide therapy (PRRT) has been recognized as a promising therapy against neuroendocrine tumors (NETs). The use of (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) in NETs has been a matter of controversy. The purpose of this study was to evaluate the long-term survival and efficacy of a second PRRT course with (177)Lu-DOTATE in patients with advanced gastroenteropancreatic (GEP) NETs. Furthermore, the value of (18)F-FDG PET/CT in these patients was evaluated. 40 patients with GEP NETs who underwent two PRRT courses with (177)Lu-DOTATATE and combined examinations with (68)Ga-DOTA-TOC and (18)F-FDG PET/CT were evaluated. After the second PRRT course, two patients (5.0%) were in partial remission, 21 patients (52.5%) in stable disease and 17 patients (42.5%) had progressive disease. The median overall survival was 122.10 months. After the second PRRT course, the median overall survival was significantly higher (p = 0.033) in the (18)F-FDG-negative group compared to the (18)F-FDG-positive group (145.50 versus 95.06 months, respectively). The median time to progression was 19.37 months. In conclusion, a second PRRT course with (177)Lu-DOTATE is an effective treatment approach for GEP NET patients with disease progression. A change in (18)F-FDG status after PRRT may predict the disease course and survival. Patients who are (18)F-FDG-negative have a significantly longer overall survival than those who are (18)F-FDG-positive.