Molecular Imaging for Response Assessment of Neuroendocrine Tumors (NET)

Assessing treatment response in neuroendocrine tumors (NET) remains a significant challenge due to their typically indolent growth and heterogenity, the frequent occurrence of disease stabilization rather than tumor shrinkage after therapy, and the inherent limitations of conventional imaging criteria. While molecular imaging-primarily somatostatin receptor (SST) PET/CT-has improved lesion detection, the absence of standardized response criteria limits its clinical utility and prevents its use as full replacement of conventional imaging. Emerging strategies, including revised thresholds for dimensional changes, criteria evaluating different features, such as lesions' density and functional tumor volumes, offer potential improvements in response evaluation but require further validation for routine clinical implementation. This review examines the current challenges in assessing NET treatment response, evaluates the strengths and limitations of available imaging modalities, and discusses emerging approaches and future directions for optimizing therapeutic monitoring in the heterogeneous panorama of NET.