Utility of Early Posttreatment PET/CT Evaluation Using FDG or ¹⁸F-FCH to Predict Response to ⁹⁰Y Radioembolization in Patients With Hepatocellular Carcinoma.

Abstract

<b>BACKGROUND</b>. Assessment of hepatocellular carcinoma (HCC) treatment response after transarterial radioembolization (TARE) is challenging, because response by conventional imaging criteria may not become apparent until 6 months after treatment. Though HCC exhibits variable avidity for FDG, some cases of HCC without avidity for FDG show avidity for ¹⁸F-fluorocholine (¹⁸F-FCH). <b>OBJECTIVE</b>. The purpose of this study was to evaluate the utility of early posttreatment evaluation by PET/CT using FDG or ¹⁸F-FCH to predict 6-month treatment response and survival after TARE in patients with HCC. <b>METHODS</b>. This retrospective study included 37 patients (mean age, 67 years; 34 men, three women) with documented HCC treated by TARE who underwent both pre-treatment FDG PET/CT and ¹⁸F-FCH PET/CT and early FDG PET/CT and/or ¹⁸F-FCH PET/CT 4-8 weeks after treatment; FDG PET/CT and ¹⁸F-FCH PET/CT examinations were performed on separate dates. Only one of 73 initially identified potentially eligible patients was excluded because of lack of HCC avidity for both FDG and ¹⁸F-FCH. Response assessment by modified RECIST (mRECIST) on multiphase CT or MRI was performed at 1 month and 6 months in 23 patients. Early responses seen on PET/CT and 1-month mRECIST response were assessed as predictors of 6-month mRECIST response. Univariable and multivariable predictors of overall survival (OS) were identified. <b>RESULTS</b>. On pretreatment PET/CT, 28 (76%) patients were FDG-positive (showed visual uptake on FDG PET/CT and tumor-to-normal liver ratio > 1.15), 15 (41%) were FCH-positive (showed visual uptake on ¹⁸F-FCH PET/CT), and six (16%) were both FDG-positive and FCH-positive. Twelve of 28 FDG-positive HCCs exhibited early response by FDG PET/CT; seven of 15 FCH-positive HCCs exhibited early response by ¹⁸F-FCH PET/CT. Twelve (52%) patients exhibited 6-month mRECIST response. Response seen on early posttreatment PET/CT exhibited 100% (12/12) sensitivity and 100% (11/11) specificity for 6-month mRECIST response, whereas 1-month mRECIST response exhibited 67% (8/12) sensitivity and 100% (11/11) specificity for 6-month mRECIST response. Response seen on early posttreatment PET/CT was a significant independent predictor of OS on univariable (hazard ratio [HR], 0.4; 95% CI, 0.2-0.9; <i>p</i> = .03) and multivariable (HR, 0.2; 95% CI, 0.1-0.8; <i>p</i> = .01) analyses. <b>CONCLUSION</b>. Early evaluation after TARE by PET/CT using FDG or ¹⁸F-FCH may pre dict 6-month response and OS in patients with HCC. <b>CLINICAL IMPACT</b>. Early posttreatment evaluation with PET/CT could help more reliably identify true nonresponders after TARE, which in turn could prompt early response-adapted therapeutic management.