Potential and Clinical Significance of 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography for Evaluating Liver Cancer Response to Lenvatinib Treatment

Background: The sensitivity of F-18-fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG-PET/CT) in hepatocellular carcinoma (HCC) is low; however, clinical evidence demonstrating its prognostic value in patients with HCC has recently been reported. This study aimed to assess the value of F-18-FDG-PET/CT as a tool for evaluating the response of HCC to lenvatinib treatment. Methods: We evaluated 11 consecutive patients with HCC diagnosed by dynamic CT or magnetic resonance imaging combined with F-18-FDG-PET/CT from April 2018 to December 2019. The tumor-to-normal liver ratio (TLR) of the target tumor was measured before and during the course of lenvatinib treatment with F-18-FDG-PET/CT (pre and post analysis, respectively), with a TLR >= 2 classified as PET-positive HCC. At the time of each evaluation, we also used the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, the modified RECIST (mRECIST), and the tumor marker alfa-fetoprotein (AFP). Results: Of 11 patients, 3 (27%) and 8 (73%) had an objective response to lenvatinib treatment at the time of post-analysis by RECIST 1.1 and mRECIST, respectively. There were 3 (27%) and 7 (64%) patients with PET-positive HCC at the time of pre- and post-analysis, respectively. There was a significant correlation between the rates of change in AFP and TLR during lenvatinib treatment (r = 0.69, p = 0.019). Based on these results, we were able to perform liver resection on 4 patients with PET-positive HCC as conversion therapy. Three samples from these patients showed poorly differentiated tumors. Conclusion: F-18-FDG-PET/CT has potential as an evaluation tool for describing biological tumor behavior and reflecting disease progression, location, and treatment response. This modality may provide useful information for considering prognosis and subsequent therapy.