Superior Response of CAP-PRRT of G3 NET When Switching to the Somatostatin Receptor Antagonist LM3: Intraindividual Proof-of-concept.

We present a 67-year-old man with inoperable metastatic G3 NET of the pancreas. The lesions were intensely positive in [68Ga]Ga-DOTATOC PET/CT and only weakly positive in the supplementary [18F]-FDG PET/CT. Peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTA-octreotate, after longstanding efficacy with repetitive retreatments over 7 years, eventually resulted only in disease stabilization without partial regression of lesions. After switching PRRT to the somatostatin receptor antagonist [177Lu]Lu-DOTA-LM3, a marked therapy response was observed, in remarkable contrast to the stable disease effect of 177Lu-octreotate seen right before. This interesting image illustrates the superior therapeutic efficacy of somatostatin antagonist PRRT over agonist-based PRRT.