Prognostic value of FDG-PET/CT findings in mucosal melanoma of the head and neck treated with carbon ion radiotherapy.

OBJECTIVE

To investigate the prognostic value of 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) in patients with mucosal melanoma of the head and neck (MMHN) treated with carbon ion radiotherapy (CIRT).

METHODS

This single-center retrospective study included patients with MMHN who underwent CIRT and FDG-PET/CT. Correlations between pre-treatment FDG-PET/CT-derived parameters, including the maximum standardized uptake variable (SUVmax), metabolic tumor volume (MTV) with a 50% threshold, total lesion glycolysis (TLG), bone marrow/liver SUVmax and mean standardized uptake variable (SUVmean) ratios, and spleen/liver SUVmax and SUVmean ratios (SLRmax, SLRmean), with clinical parameters and prognosis were statistically analyzed.

RESULTS

A total of 32 patients with MMHN were enrolled (median age, 72.5 years). The tumor stages were distributed as follows: T3, 17 patients; T4a, 14 patients; T4b, one patient. The median total observation period was 22.6 months, the median overall survival (OS) was 21.6 months, and the median progression-free survival (PFS) was 11.5 months. Thirteen patients (40.6%) died, 10 (31.3%) experienced local recurrence, and 19 (59.4%) had distant metastases during the observation period. The 1 and 3-year survival rates were 78.1% and 62.5%, respectively. FDG-PET/CT showed pronounced positive uptake for all tumors (median SUVmax: 13.8, range 2.7-33.0). SLRmax was high in patients with negative programmed death-ligand 1 expression in the tumor (p = 0.05). PFS was shorter in patients with a high MTV (p = 0.018). In the multivariate analysis, MTV was an independent prognostic factor for PFS (hazard ratio, 2.60; 95% confidence interval, 1.065-6.345; p = 0.036). MTV and TLG were not predictive of OS in the univariate analysis.

CONCLUSIONS

FDG-PET/CT showed a strong positive uptake for MMHN. FDG-PET/CT-derived imaging parameters may be significant prognostic biomarkers for predicting tumor progression in patients with MMHN.