NIMG-80. SKULL BASE CHORDOMA: CORRELATION OF18F-FDG PET/CT FINDINGS WITH PATHOLOGICAL FEATURES AND CLINICAL COURSE

Abstract

Abstract OBJECTIVE This study aimed to evaluate 18F-fluorodeoxyglucose (FDG)-PET/CT findings, histopathological results, and clinical outcomes in patients with skull base chordoma. METHODS This retrospective study included patients who underwent first or repeat excision/biopsy for skull base chordoma at our institution between 2010 and 2019, with preoperative FDG-PET/CT. We assessed the SUVmean, SUVmax, lesion to white matter SUVmax/SUVmean ratio (L/N ratio), MIB-1 index, and occurrence of postoperative recurrence and metastasis. Statistical analysis was performed using Spearman's rank correlation coefficient and the Mann-Whitney U test. RESULTS Of the 17 participants, 52% were male, with a median age of 49 years (Interquartile Range: IQR 32-69). Among them, 41% were primary cases, and the median follow-up period was 51 months (IQR 32-77). The median SUVmax was 5.2 (IQR 3.9-6.2), SUVmean was 3.6 (IQR 3.1-5.1), L/N ratio was 1.5 (IQR 1.2-2.3), and MIB-1 index was 7.5% (IQR 2-10). Only SUVmax demonstrated a significant positive correlation with the MIB-1 index (ρ=0.556, p=0.021). Out of the 16 surgeries, 11 (69%) resulted in recurrence, while 4 of the total 17 cases (24%) showed metastasis. There were no significant differences in SUVmax, SUVmean, L/N ratio, and MIB-1 index between recurrence and non-recurrence groups. However, the MIB-1 index showed significant difference between metastasis and non-metastasis groups (p=0.0055). CONCLUSION In skull base chordoma, there was a significant correlation between the SUVmax on FDG-PET and the MIB-1 index. The MIB-1 index was significantly higher in the metastasis group. However, no significant correlation was found between SUVmax and distant metastasis, possibly due to the small sample size.