Intratumoral serotonin might decrease the efficacy of PRRT in ileal neuroendocrine tumors

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Introduction: Partial remission can be achieved by peptide receptor radionuclide therapy (PRRT) in only roughly 20% of patients with midgut neuroendocrine tumor (NET). This low remission rate can be due to the radioprotective role of stored intracytoplasmic serotonin in NET cells. If blocked, e.g. by telotristatethyl, PRRT efficacy might be increased.

Aim(s): With this aim, we analysed a) the distribution and concentration of serotonin in NET cells and matrix, b) the tryptophanhydroxlase enzyme 1 (TPH-1) expression in NET cells, and c) TPH-1 gene expression in fresh frozen tumor specimens (FF).

Materials and methods: 21 patients (F:M::12:9) with ileal NETs and 9 metastatic FF lesions were studied. The following markers were immunohistochemically analysed (distribution and semiquantitation): somatostatin receptor subtype 2 and 5, Ki67, serotonin and TPH1. Additionally, TPH1 gene expression was determined.

Conference: 18th Annual ENETS Concerence (2021)

Presenting Author: Prasad V

Authors: Prasad V, Klöppel G, Lupp A, Wirtz R, Kaemmerer D,

Keywords: Ileal NET, serotonin, radioprotector, PRRT, immunohistochemistry, TPH1,