To investigate the diagnostic value of 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET), as an imaging biomarker, for predicting pathological response and prognosis of unresectable hepatocellular carcinoma (HCC) patients treated with Lenvatinib and programmed cell death protein 1 (PD-1) inhibitors as a conversion therapy. This evidence concerns the gene PDCD1 and hepatocellular carcinoma.