First Successful In-Human Application of 225Ac-DOTA-LM3 Mono-PRRT for the Treatment of an Otherwise Therapy-Resistant Neuroendocrine Tumor (NET G3).

We present a case of a 60-year-old woman diagnosed with metastasized small bowl NET G3 with high hepatic tumor burden and highly glucometabolic (FDG-avid) disease. In the postchemotherapy setting with progressive disease, the patient underwent PRRT with 177Lu-DOTA-octreotate and 225Ac-DOTA-octreotate initially resulting in stable disease. In a novel approach, 225Ac-DOTA-LM3 (somatostatin receptor antagonist) was administered, leading to a favorable treatment response in the 18F-FDG PET/CT scan. This interesting image illustrates the promising antitumor potential of alpha-sst2 antagonist PRRT with 225Ac-DOTA-LM3, and to the best of our knowledge, it is the first documented evidence of superiority over standard alpha-PRRT from intraindividual comparison.