A method of treating a somatostatin receptor over-expressing cancer in a subject, comprising administering to the subject a combination of a peptide receptor radionuclide therapeutic (PRRT) agent and one or two immuno-oncology (I-O) therapeutic agent(s), wherein said I-O therapeutic agent(s) is(are) selected from the group consisting of an LAG-3 inhibitor, a TIM-3 inhibitor, a GITR angonists, a TGF-β inhibitor, an IL15/IL-15RA complex, and a PD-1 inhibitor, wherein said PD-1 inhibitor is selected from the group consisting of Spartalizumab, Pembrolizumab, Pidilizumab, Durvalomab, Atezolizumab, Avelumab, MED10680, REGN2810, TSR-042, PF-06801591, BGB-A317, BGB-108, INCSHR1210, and AMP-224.