AUTHOR=Di Franco Martina , Durmo Rexhep , Di Paolo Maria Liberata , Giacosa Roberto , BannĂ² Elisa , Ambrosini Valentina , Filice Angelina TITLE=Case Report: PRRT in a patient with Zollinger-Ellison syndrome. The management of gastrointestinal complications JOURNAL=Frontiers in Oncology VOLUME=Volume 15 - 2025 YEAR=2025 URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2025.1590478 DOI=10.3389/fonc.2025.1590478 ISSN=2234-943X ABSTRACT=Zollinger-Ellison Syndrome (ZES) is a rare condition characterized by excessive gastric acid secretion due to gastrin-producing neuroendocrine tumors. Peptide Receptor Radionuclide Therapy (PRRT) with [177Lu]Lutetium Oxodotreotide is an effective treatment for advanced neuroendocrine tumors, including those associated with ZES. However, the gastrointestinal toxicity induced by ZES can complicate the administration of PRRT. We present a case of a patient with metastatic G2 neuroendocrine tumor of the duodenum and ampulla of Vater who experienced severe gastrointestinal complications after the first PRRT cycle due to exacerbated ZES. The implementation of a prophylactic treatment with high-dose proton pump inhibitors before and after the subsequent PRRT cycles allowed for the successful completion of the therapy. This case highlights the importance of considering ZES-related complications in patients undergoing PRRT. Proactive management with high dose acid-suppressing therapy can significantly improve patient tolerance and treatment outcomes. Further research is needed to optimize the management of ZES patients undergoing PRRT.