Towards tailored radiopeptide therapy.

PURPOSE Somatostatin receptor-targeted radiopeptide therapy is commonly performed using single radioisotopes. We evaluated the benefits and harms of combining radioisotopes in radiopeptide therapy in patients with neuroendocrine tumor. METHODS Using multivariable-adjusted survival analyses and competing risk analyses we evaluated outcomes in patients with neuroendocrine tumor receiving (90)Y-DOTATOC, (177)Lu-DOTATOC or their combination. RESULTS (90)Y-DOTATOC plus (177)Lu-DOTATOC treatment was associated with longer survival than (90)Y-DOTATOC (66.1 vs. 47.5 months; n = 1,358; p < 0.001) or (177)Lu-DOTATOC alone (66.1 vs. 45.5 months; n = 390; p < 0.001). (177)Lu-DOTATOC was associated with longer survival than (90)Y-DOTATOC in patients with solitary lesions (HR 0.3, range 0.1 - 0.7; n = 153; p = 0.005), extrahepatic metastases (HR 0.5, range 0.3 - 0.9; n = 256; p = 0.029) and metastases with low uptake (HR 0.1, range 0.05 - 0.4; n = 113; p = 0.001). (90)Y-DOTATOC induced higher hematotoxicity rates than combined treatment (9.5% vs. 4.0%, p = 0.005) or (177)Lu-DOTATOC (9.5 vs. 1.4%, p = 0.002). Renal toxicity was similar among the treatments. CONCLUSIONS Using (90)Y and (177)Lu might facilitate tailoring radiopeptide therapy and improve survival in patients with neuroendocrine tumors.