Re-challenge strategies in neuroendocrine tumours: adding another arrow in the quiver?

Retreatment strategies in neuroendocrine tumours have shown promising clinical activity, yet evidence to guide patient selection and optimal treatment modalities remains limited. In this narrative review, we summarise the currently available data on systemic retreatment approaches (retreatment and reintroduction strategies) and highlight biological and clinical key factors - such as the role of MGMT expression, tumour grade, and treatment-free interval - that may inform clinical decision-making. We also outline critical priorities for future clinical trial design, including the integration of predictive biomarkers and the development of standardized retreatment protocols. Further prospective, biomarker-driven studies are required not only to refine patient selection but also to establish whether rechallenge strategy may represent a biologically reasonable and clinically meaningful strategy.