Prognostic value of 18f-fluorodeoxyglucose positron emission tomography-computed tomography in predicting survival in patients with unresectable metastatic melanoma to the liver undergoing yttrium-90 radioembolization.

PURPOSE: To investigate the prognostic value of (18)F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) in predicting survival in patients with unresectable metastatic melanoma to the liver undergoing yttrium-90 ((90)Y) radioembolization.

MATERIALS AND METHODS: A retrospective review of 12 patients with unresectable hepatic melanoma metastases (5 patients with cutaneous metastases, 7 patients with ocular metastases) who underwent (18)F-FDG PET-CT before (90)Y was performed. Metabolically significant tumors, defined as having a long-axis diameter ≥ 1 cm and maximum standardized uptake value (SUV(max)) ≥ 2.5, were identified on (18)F-FDG PET-CT. SUV(max), glycolytic activity, and volume were determined for each tumor. Overall SUV(max), total tumor glycolytic activity (TGA), total metabolic tumor volume (MTV), and metabolic tumor burden (MTB) based on percentage of liver involvement (MTV/total liver volume) were calculated. Kaplan-Meier method, life-table analysis, and Cox proportional hazards model were used for statistical analysis.

RESULTS: Median SUV(max) was 10.9 (range, 4.6-15.3), median TGA was 377.0 SUV/cm(3) (range, 53.6-20,393.4 SUV/cm(3)), median MTV was 85.4 cm(3) (range, 11.5-2,504.1 cm(3)), and median MTB was 5.5% (range, 0.1%-54.0%). MTB was found to be a significant negative prognostic marker of survival on univariate (P = .020) and multivariate (P = .018) analyses accounting for age and duration from metastatic diagnosis to first (90)Y treatment. A 60th percentile MTB of 7.0% (hazard ratio, 5.704; P = .040) was a statistically significant cutoff. Median survivals from first (90)Y treatment in patients with MTB < 7.0% and ≥ 7.0% were 10.8 months (95% confidence interval [CI], 6.8-14.8) and 4.7 months (95% CI, 1.6-7.8), respectively. SUV(max) (P = .422), TGA (P = .064), and MTV (P = .065) were not found to be statistically significant.

CONCLUSIONS: MTB based on (18)F-FDG PET-CT performed before treatment was found to be a negative prognostic factor for patient survival after (90)Y radioembolization for unresectable metastatic melanoma to liver.