[F]SiTATE-PET/CT for detection of pheochromocytomas and paragangliomas: comparison of biochemical secretion, genotype and imaging metrics.

Background: Somatostatin-receptor (SSTR)-targeting PET/CT is widely used for diagnosis and disease monitoring of pheochromocytoma / paraganglioma (PPGL). The aim of this study was to assess the potential of the novel SSTR-targeting tracer [F]SiTATE in diagnosing PPGL by comparing imaging parameters to tumor marker levels and secretory activity in a small cohort of patients diagnosed with this rare tumor type.

Methods: This retrospective study included 34 patients with histologically confirmed PPGL who underwent [F]SiTATE-PET/CT at LMU University Hospital Munich between 10/2020 and 02/2024 as well as hormonal laboratory analysis within up to 100 days. Imaging parameters - standardized uptake values (SUVmax, SUVmean), metabolic tumor volume (MTV), and total lesion uptake (TLU) - were analyzed. Uptake was normalized to liver background (SUVmaxr, SUVmeanr). Radioligand uptake of biochemical subtypes and genotypes was compared with Mann-Whitney-U test. Correlation was tested using Spearman´s rank correlation test.

Results: The patient-based detection rate of [F]SiTATE-PET was 96.6%. A moderate correlation was found between MTV and TLU with chromogranin A (r = 0.570-0.608, p < 0.005) and with biochemical secretion (r = 0.466-0.576, p < 0.05). Hereditary PPGL with Cluster 1 genotype showed stronger [F]SiTATE uptake compared to sporadic PPGL (SUVmeanr: p = 0.032; SUVmaxr: p = 0.051). A subgroup comparison with [⁶⁸Ga]Ga-DOTATOC-PET/CT revealed no significant difference in uptake metrics or tumor-to-background ratios.

Conclusion: This is the first clinical evaluation of [F]SiTATE-PET/CT in patients with PPGL. MTV and TLU measured with [F]SiTATE-PET/CT correlated well with the tumor marker chromogranin A in serum and with (nor)metanephrines in urine and plasma. Within the limits imposed by the small cohort, our results suggest that TLU and MTV in [F]SiTATE-PET/CT could be used as SSTR imaging biomarker for monitoring of disease progression and secretory activity in patients with PPGL.