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

Peptide receptor radionuclide therapy (PRRT) has been recognized as a promising therapy against neuroendocrine tumors (NETs). The use of ¹⁸F-fluorodeoxyglucose (¹⁸F-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 ¹⁷⁷Lu-DOTATE in patients with advanced gastroenteropancreatic (GEP) NETs. Furthermore, the value of ¹⁸F-FDG PET/CT in these patients was evaluated. 40 patients with GEP NETs who underwent two PRRT courses with ¹⁷⁷Lu-DOTATATE and combined examinations with ⁶⁸Ga-DOTA-TOC and ¹⁸F-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 ¹⁸F-FDG-negative group compared to the ¹⁸F-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 ¹⁷⁷Lu-DOTATE is an effective treatment approach for GEP NET patients with disease progression. A change in ¹⁸F-FDG status after PRRT may predict the disease course and survival. Patients who are ¹⁸F-FDG-negative have a significantly longer overall survival than those who are ¹⁸F-FDG-positive.