Clinical significance of 2-[ super(18)F]fluoro-2-deoxy-d-glucose positron emission tomography for the assessment of super(131)I-metaiodobenzylguanidine therapy in malignant phaeochromocytoma

Purpose: The aim of this study was to evaluate the significance of 2-[ super(18)F]fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) in the assessment of the therapeutic response to super(131)I-metaiodobenzylguanidine (MIBG) in malignant phaeochromocytoma. Methods: We reviewed the records of 11 patients (7 men and 4 women) with malignant phaeochromocytoma who underwent super(131)I-MIBG therapy (100-200 mCi). super(18)F-FDG PET and serum catecholamine assays were performed 3 months before and after the first dose of super(131)I-MIBG. FDG uptake was evaluated in the observed lesions using the maximum standardised uptake value (SUV sub(max)). The average SUV sub(max) of all lesions (ASUV) was calculated. If more than five lesions were identified, the average SUV sub(max) of the five highest SUV sub(max) (ASUV5) was calculated. The ratio of pre- and post-therapy values was calculated for the highest SUV sub(max) (rMSUV), ASUV (rASUV), ASUV5 (rASUV5), CT diameter (rCT) and serum catecholamine (rCA). Responder (R) and non-responder (NR) groups were defined after a clinical follow-up of at least 6 months according to changes in symptoms, CT, magnetic resonance imaging (MRI) and super(123)I-MIBG scan. Results: Post-therapy evaluation revealed five R and six NR patients. The size of the target lesions was not significantly different before and after therapy (p>0.05). However, ASUV and ASUV5 were significantly lower in the R group (rASUV 0.64+/-0.18, rASUV5 0.68+/-0.17) compared to the NR group (rASUV 1.40+/-0.54, rASUV5 1.37+/-0.61) (p