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 90Y beta emitter for larger lesions and the lower energy 177Lu for smaller lesions has been postulated in the literature.The aim of the study was to evaluate combined 90Y/177Lu-DOTATATE therapy in comparison to 90Y-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 90Y-DOTATATE, whereas group B (n=25) received the 1:1 90Y/177Lu-DOTATATE. The administered activity was based on 3.7 GBq/m2 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 (90Y/177Lu-DOTATATE) provides longer overall survival than with a single radioisotope (90Y-DOTATATE) and the safety of both methods is comparable.