<sup>18</sup>F-Fluorodeoxyglucose Uptake in Hepatocellular Carcinoma as a Useful Predictor of an Extremely Rapid Response to Lenvatinib

Background and Aims: This study aimed to identify the utility of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) as a predictor of the response of hepatocellular carcinoma (HCC) to lenvatinib. Methods: We evaluated 28 consecutive patients with HCC diagnosed by dynamic CT or magnetic resonance imaging combined with 18F-FDG-PET/CT. The tumor-to-normal liver standardized uptake value ratio (TLR) of the target tumor was measured before treatment using 18F-FDG-PET/CT, with a TLR ≥2 classified as a high potential for malignant HCC. The treatment response was evaluated 2 weeks after the initiation of lenvatinib using modified Response Evaluation Criteria in Solid Tumors. Results: Of the 28 patients, 12 (43%) presented with a TLR ≥2. Evaluation of the treatment response at 2 weeks in these 12 patients revealed that 2 (17%) exhibited a complete response, 8 (67%) a partial response, 2 (17%) stable disease, and none with progressive disease. Therefore, 10 of the 12 patients (83%) experienced an objective response to lenvatinib. On the other hand, 7 of the 16 patients with a TLR <2 (44%) experienced an objective response. Thus, the objective response rate was higher in patients with a TLR ≥2 than in those with a TLR <2. Multivariate logistic regression analysis revealed that a TLR ≥2 (odds ratio 10.53; p = 0.028) is a useful predictor of an early objective response at 2 weeks. Conclusion: Patients with unresectable HCC showed a good early treatment response to lenvatinib. High TLR (≥2) may be a useful predictor of an extremely rapid treatment response.