Genetic status determines 18 F-FDG uptake in pheochromocytoma/paraganglioma.

Tiwari A1, Shah N1, Sarathi V2, Malhotra G3, Bakshi G4, Prakash G4, Khadilkar K1, Pandit R1, Lila A1, Bandgar T1.

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Abstract

INTRODUCTION:

Although few studies have demonstrated utility of 18 F- fluoro-2-deoxy-d-glucose positron emission tomography/computerised tomography (18 F-FDG PET/CT) in benign pheochromocytoma/paragangliomas (PCC/PGLs), there limited data on factors predicting the FDG uptake in PCC/PGL.

METHODS:

The study was conducted at a tertiary health care centre. In addition to the routine investigations, all patients (n = 96) with PCC/PGL were evaluated with 18 F-FDGPET/CT and majority (n = 78) underwent 131 I-metaiodobenzyl guanidine (131 I-MIBG) scintigraphy. Forty-three patients also underwent testing for germline mutations in five PCC/PGL susceptibility genes (VHL, RET, SDHB, SDHC and SDHD) and all patients were evaluated clinically for neurofibromatosis-1.

RESULTS:

The study included 96 patients with PCC/PGL(82 benign and 14 malignant). FDGSUVmax was significantly higher for malignant than benign PCC/PGL(P = 0.009) and for extra-adrenal PGL than adrenal PCC (P = 0.017). In subgroup analysis, metanephrine-secreting PCC and non-secretory PCC had significantly lower FDG SUVmax than normetanephrine-secreting PCC (P = 0.017, P = 0.038 respectively), normetanephrine-secreting-sympathetic PGL (P = 0.008, P = 0.019 respectively) and non-secretory sympathetic PGL (P = 0.003, P = 0.009 respectively). Patients with mutations in cluster 1 genes (n = 14) had significantly higher FDG SUVmax than those with mutations in cluster 2 genes (n = 4) (P = 0.04). Sensitivities of 131 I-MIBG and 18 F-FDG PET/CTwere 77.78% and 100% for cluster 1 genes-related PCC/PGL whereas they were 100% and 50% for cluster 2 genes-related PCC/PGL, respectively. Multivariate regression analysis of mutation positive patients identified genetic status as the only independent predictor of FDG SUVmax.