Effect of peptide receptor radionuclide therapy (PRRT) with tandem isotopes — [90Y]Y/[177Lu]Lu-DOTATATE in patients with disseminated neuroendocrine tumours depending on [18F]FDG PET/CT qualification in Polish multicentre experience — do we need [18F]FDG PET/CT for qualification to PRRT?

Introduction: Peptide receptor radionuclide therapy (PRRT) using radiolabelled somatostatin analogues is a treatment option for patients with disseminated neuroendocrine tumours (NET). The aim of the study was the evaluation of the role of [18F]FDG PET/CT in predicting response, progression-free survival (PFS) and overall survival (OS) after tandem therapy [90Y]Y/[177Lu]Lu-DOTATATE. Material and methods: Seventy-five patients with histopathologically proven NET G1 and G2 were included in the study. Before treatment [68Ga]Ga-DOTATATE PET/CT and [18F]FDG PET/CT was performed. Patients were treated with [90Y]Y/[177Lu]Lu-DOTATATE (1:1) with mixed amino-acid infusion for kidney protection. Results: Progression-free survival was 22.2 months for [18F]FDG-positive patients and 59.3 months for [18F]FDG-negative patients (p = 0.003). The OS from diagnosis (OS-D) and from the start of PRRT (OS-T) was not reached in [18F]FDG-negative patients, and in [18F]FDG-positive patients it was 71.8 months and 55.8 months, respectively. The observed overall one-year survival in [18F]FDG-positive vs. [18F]FDG-negative patients was 96.8% vs. 99.1%, two-year survival was 88.9% vs. 96%, and five-year survival was 58.8% vs. 88%, respectively. The one-year and two-year risk of progression was 15% vs. 58.9% in [18F]FDG-positive patients and 11% vs. 32% in [18F]FDG-negative patients. The objective response rate (ORR) [18F]FDG-positive vs. [18F]FDG-negative patients was 41.7% vs. 17%. Conclusions: [18F]FDG-positive patients have statistically significant shorter survival parameters than [18F]FDG-negative patients. The risk of progression in [18F]FDG-positive vs. [18F]FDG-negative patients in one-year follow-up is comparable, whereas in two-year follow-up it is nearly two times higher for [18F]FDG PET/CT-positive patients.