SSTR2 and cancer: However, only a handful of endoradiotherapies have received FDA approval for cancer treatment, starting with 131I (15), 131I-labeled radioligands (16), and the more recent addition of β-emitting radioligands like 177Lu-DOTATATE (177Lu-DOTA-0-Tyr3-Octreotate) (17) and 177Lu-PSMA-617 (18) targeting tumors overexpressing somatostatin receptor 2 (SSTR2) and prostate-specific membrane antigen (PSMA), respectively.