Correlation of 68Ga-DOTATATE and 18F-FDG PET/CT Uptake Parameters with PASS and GAPP Scores in Pheochromocytoma

Abstract

Background: Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors with highly variable biological behavior. Somatostatin receptor (SSTR)-based imaging with 68Ga-DOTATATE PET/CT has become an important functional imaging modality for evaluating these tumors. In contrast, 18F-FDG PET/CT reflects tumor glucose metabolism and has been associated with more aggressive tumor phenotypes. This study aimed to evaluate associations between 68Ga-DOTATATE and 18F-FDG PET/CT-derived parameters and postoperative PASS and GAPP scores in patients with pheochromocytoma. Materials and Methods: Thirty patients with histologically confirmed pheochromocytoma who underwent 68Ga-DOTATATE PET/CT were retrospectively reviewed. Among them, 11 patients also underwent 18F-FDG PET/CT and were included in the comparative imaging analysis. Results: Tumor size showed strong positive correlations with both SSTR-TV (ρ = 0.725, p < 0.001) and SSTR-TL (ρ = 0.755, p < 0.001). 18F-FDG SUVmax was positively correlated with PASS (ρ = 0.616, p = 0.044) and GAPP scores (ρ = 0.720, p = 0.012). 18F-to-68Ga SUVmax ratio showed significant positive correlations with the PASS (ρ = 0.737, p = 0.010) and the GAPP score (ρ = 0.661, p = 0.027). Conclusions: In this exploratory study, 68Ga-derived volumetric parameters were primarily associated with tumor size, whereas 18F SUVmax and the 18F/68Ga SUVmax ratio were associated with PASS and GAPP scores in the small dual-tracer subgroup. These findings require validation in larger cohorts.