Contrary to prior assumptions suggesting that internalization is a crucial factor for the efficacy of short-ranged IC and Auger electrons, the non-internalizing somatostatin antagonist [161Tb]Tb-DOTA-LM3 has shown to be substantially more effective than its 177Lu-based counterpart in inhibiting in vitro tumor cell viability, being up to 100 times more potent. Here, SST is linked to neoplasm.