[¹¹C]Methionine PET uptake kinetics in corticotroph pituitary neuroendocrine tumors.

[11C]Methionine ([11C]MET) PET provides high sensitivity to localize corticotroph pituitary neuroendocrine tumors (PitNETs) in de novo Cushing’s disease but remains inconclusive in up to 20% of cases. Current PET protocols rely on late acquisitions (20–40 min post-injection). Since other endocrine tumors present earlier peak tracer uptake, corticotroph PitNETs might also exhibit early differential amino acid uptake, compared to the normal pituitary gland. This exploratory study based on data derived from a previously registered prospective multicenter cohort study (ClinicalTrials.gov identifier: NCT03346954) included 15 patients with pathologically confirmed corticotroph PitNETs accurately localized using MRI. Kinetic analysis showed rapid early uptake in PitNETs and normal pituitary gland, followed by a significant decline over time, with consistently higher uptake in PitNETs (p < 0.05), but no statistically significant difference in temporal uptake pattern (p = 0.09). Early uptake slope and peak uptake were significantly higher in PitNETs compared to normal gland (p < 0.01), with moderate-to-high discriminative performance (area under the curve 0.78; 95%CI 0.60–0.94 and 0.86; 95%CI 0.69–0.98, respectively). Time-to-peak showed no statistically significant discriminative value. These findings suggest that kinetic parameters of [¹¹C]MET PET, particularly early slope and peak uptake, may provide complementary information to static PET for PitNET characterization.