PET/CT contouring techniques in neuroendocrine neoplasms: a state-of-the-art scoping review

Neuroendocrine neoplasms (NENs) are often metastatic at diagnosis and show great variation in primary site and biological behaviour. Although PET is often used to image NENs, contouring is challenging because NEN lesions are heterogenous. This scoping review examines the literature on NEN contouring in clinical settings.

The scoping review follows the PRISMA-ScR guidelines. Published studies between 2010 and 2025 and conference abstracts and proceedings between 2023 and 2025 were included. Eligible studies included studies with at least 5 patients with NEN, involved PET imaging analysis with the measurement of at least one quantitative variable, and used a thresholding method to determine lesion contours.

Thirty-seven articles and 17 conference abstracts were included in the review. Sixteen articles investigated flat contouring methods, 11 investigated relative contouring approaches, 3 investigated both, 6 used manual contouring exclusively, and 1 did not explicitly describe the contouring method. Twenty-five articles used radiopharmaceuticals targeting somatostatin receptors (SSTR) only, 5 used [¹⁸F]FDG only, 6 used dual tracers, and 1 used [¹⁸F]F-DOPA. Included studies confirmed the prognostic importance of SSTR and [¹⁸F]FDG volumetric parameters and [¹⁸F]FDG SUV_max. There was little agreement regarding the prognostic value of other measurable quantitative parameters.

Flat contouring methods were most commonly used for the contouring of NENs and are clinically applicable. Therefore, investigating the prognostic value of quantitative parameters derived from flat contouring methods could yield an optimised NEN lesion contouring methodology.