Prognostic value of ¹⁸F-DOPA PET/CT at the time of recurrence in patients affected by neuroblastoma

Purpose: The aim of this study was to investigate the relationship between 123I-metaiodobenzylguanidine (MIBG) scan semi-quantification and a new 18F-DOPA positron emission tomography (PET)/CT score in patients with suspected or documented neuroblastoma (NB) relapse and to assess the association between these two parameters and progression-free survival (PFS)/overall survival (OS). Methods: We analysed 24 NB patients who had undergone 123I-MIBG and 18F-DOPA PET/CT scans at the time of suspected relapse, after applying a proper scoring system for each scan. In time-to-event analyses, the score distributions were regarded as continuous and were categorized in tertiles and medians. We used Kaplan-Meier curves and Cox proportional hazard models for PFS and OS in order to estimate the independent prognostic impact of 123I-MIBG and 18F-DOPA PET/CT scans. Results: The 123I-MIBG and 18F-DOPA scores were highly and positively correlated (Spearman's rho=0.8, p<0.001). Over a median follow-up of 14 months (range 6-82), 12 cases of disease progression and 6 deaths occurred. Multivariate Cox models showed a higher risk of disease progression [hazard ratio (HR) 17.0, 95 % confidence interval (CI) 2.7-109] in NB patients with 123I-MIBG score>3 (3rd tertile) and an even higher risk (HR:37.2, 95 % CI 2.4-574) in those with 18F-DOPA whole-body metabolic burden (WBMB) >7.5 (median), after adjustment for all main clinical/pathological factors considered. Kaplan-Meier analyses showed a significant association with OS (log-rank p=0.01 and p=0.03 for 123I-MIBG and 18F-DOPA WBMB, respectively). Conclusion: Our results confirm the good agreement between 18F-DOPA PET/CT and 123I-MIBG scan in patients affected by NB relapse. In time-to-event analyses, 123I-MIBG scan and 18F-DOPA PET/CT scores were independently and significantly associated with disease progression.