Evaluating treatment response of radioembolization in intermediate-stage hepatocellular carcinoma patients using ¹⁸F-fluoroethylcholine PET/CT

The aim of this study was to evaluate ¹⁸F-fluoroethylcholine PET/CT as a metabolic imaging technique for the assessment of treatment response to ⁹⁰Y radioembolization in patients with locally advanced hepatocellular carcinoma (HCC). Methods: Thirty-four HCC patients undergoing 78 ¹⁸F-fluoroethylcholine PET/CT scans were identified for this study. Patients with initial or follow-up metastastic disease (n = 9) were excluded at the time point of the metastatic occurrence as well as patients with negative α-fetoprotein (AFP; n = 1), resulting in 24 patients and 57 scans that were eligible. All patients were scheduled for radioembolization and underwent 1 pretherapeutic and at least 1 posttherapeutic ¹⁸F-fluoroethylcholine PET/CT scan. Volume-of-interest analysis and volume-of-interest subtractions were performed. Maximum, mean, and peak standardized uptake value (SUV) analysis was performed, and the total intrahepatic ¹⁸F-fluoroethylcholine positive tumor volume (FEC-PTV) and tumor-to-background ratio were assessed. Statistical analysis was performed using a decreasing AFP of at least 20% as a standard of reference for therapy response including receiver-operating-characteristic analyses as well as descriptive and correlation analyses and multiple logistic regression. Results: Fourteen follow-up examinations were categorized as responder and 19 follow-up examinations as nonresponder. Absolute AFP values did not correlate with SUV parameters (P = 0.055). In receiver-operating-characteristic analyses, the initial mean SUV, Δmaximum SUV, and Δtumor-to-background ratio demonstrated the highest area under the curve, 0.84 (P = 0.009), 0.83 (P = 0.011), and 0.83 (P = 0.012), respectively, resulting in a positive prediction of 82%, 83%, and 91% at the respective cutoff points. When multiple logistic regression analysis was applied, this resulted in an area under the curve of 0.90 (P = 0.001), with a positive prediction of 94% and a sensitivity of 94%. The FEC-PTV did not reach significance in the presented dataset. Conclusion: ¹⁸F-fluoroethylcholine PET/CT demonstrates a high potential for follow-up assessment in the context of radioembolization in patients with locally advanced, but nonmetastatic, HCC and initially elevated AFP, possibly enabling early therapy monitoring independent of morphology.