The use of 99mTc-HYNIC-TOC and 18F-FDG PET/CT in the evaluation of duodenal neuroendocrine tumor with atypical and extensive metastasis responding dramatically to a single fraction of PRRT with 177Lu-DOTATATE.

This report describes a case of extensive diffuse bone marrow involvement with bilateral breast metastases from duodenal neuroendocrine tumor giving rise to a superscan-like appearance on somatostatin receptor-targeted (99m)Tc-hydrazinonicotinamide-TOC scintigraphy. The metastatic lesions demonstrated partial concordance with (18)F-FDG PET/CT findings, signifying varying tumor biology and heterogeneity among metastatic lesions in the same individual, as illustrated with a dual-tracer approach. There was a dramatic symptomatic and biochemical response and better health-related quality of life with a single fraction of peptide receptor radionuclide therapy with (177)Lu-DOTATATE, and radiologically there was stable disease at that point.