Prognostic value of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography in patients with combined hepatocellular-cholangiocarcinoma

Purpose: The prognostic value of pretreatment ¹⁸F-fluorodeoxyglucose positron emission tomography with computed tomography (FDG PET/CT) was assessed in patients with combined hepatocellular-cholangiocarcinoma (cHCC-CC). Methods: A total of 46 patients with cHCC-CC who underwent FDG PET/CT before treatment were retrospectively analysed. Tumour FDG avidity was measured in terms of the tumour-to-normal liver standardized uptake value ratio (TLR) of the primary tumour on FDG PET/CT. The prognostic significance of TLR using the median value of 3.4 as the cut-off value and other clinical variables was assessed using Cox proportional hazards regression models. Differences in progression-free survival (PFS) and overall survival (OS) in relation to TLR were examined by the Kaplan-Meier method. Results: During a median follow-up period of 29 months, 29 patients (63.0%) showed tumour recurrence or progression, and 25 patients (54.4%) died from cancer. Higher TLRs (>3.4) were associated with larger tumour size (p = 0.007) and higher tumour stage (p = 0.030). In a univariable analysis, TLR, tumour stage and CEA were significant prognostic predictors. In a multivariable analysis, TLR was an independent predictor of PFS (HR 5.19, 95% CI 1.80–15.01; p = 0.002) and OS (HR 3.95, 95% CI 1.27–12.24; p = 0.017). Patients with a higher TLR showed significantly worse PFS (2-year survival rate 17.8% vs. 62.9%; p = 0.001) and OS (2-year survival rate, 39.1% vs. 77.3%; p = 0.001) than those with a lower TLR. Conclusion: Pretreatment TLR of the primary tumour measured on FDG PET/CT is an independent predictor of survival in patients with cHCC-CC.