Clinical results of radionuclide therapy of neuroendocrine tumours with (90)Y-DOTATATE and tandem (90)Y/(177)Lu-DOTATATE: which is a better therapy option?

PURPOSE: Peptide receptor radionuclide therapy (PRRT) using radiolabelled somatostatin analogues is a treatment option for patients with disseminated neuroendocrine tumours (NET). A combination treatment using the high-energy (90)Y beta emitter for larger lesions and the lower energy (177)Lu for smaller lesions has been postulated in the literature.The aim of the study was to evaluate combined (90)Y/(177)Lu-DOTATATE therapy in comparison to (90)Y-DOTATATE alone. METHODS: Fifty patients with disseminated NET were included in the study prospectively and divided into two groups: group A (n = 25) was treated with (90)Y-DOTATATE, whereas group B (n = 25) received the 1:1 (90)Y/(177)Lu-DOTATATE. The administered activity was based on 3.7 GBq/m(2) body surface area in three to five cycles, with amino acid infusion for nephroprotection. RESULTS: The median overall survival time in group A was 26.2 months while in group B median survival was not reached. Overall survival was significantly higher in group B (p = 0.027). Median event-free survival time in group A was 21.4 months and in group B 29.4 months (p > 0.1). At the 12-month follow-up, comparison of group A vs group B showed stable disease (SD) in 13 vs 16 patients, disease regression (RD) in 5 vs 3 patients and disease progression (PD) in 3 vs 4 patients; 4 and 2 patients died, respectively. The 24-month follow-up results were SD in nine vs ten patients, RD in one patient vs none and PD in four patients in both groups; three and four patients died, respectively. Side effects were rare and mild. CONCLUSION: The results indicate that therapy with tandem radioisotopes ((90)Y/(177)Lu-DOTATATE) provides longer overall survival than with a single radioisotope ((90)Y-DOTATATE) and the safety of both methods is comparable.