Introduction

Liver cancer is the fourth most common cause of cancer-related deaths worldwide. Hepatocellular carcinoma (HCC) accounts for over 80% of all liver cancers and is one of the most prevalent malignancies. Chronic hepatitis B or C is the primary cause of HCC, representing 80% of all HCC cases globally. The main treatment options for HCC include local ablation, surgical resection, or liver transplantation (LT). LT is considered the best option for radical treatment of early-stage HCC, but about 20-30% of patients experience recurrence after LT. MVI is one of the critical histological features for HCC prognosis, referring to the microscopic invasion of tumor cells into vascular endothelial cells, including the microvessels of the portal vein, hepatic artery, and lymphatic vessels. MVI has been shown to be an independent predictor of HCC recurrence. Therefore, assessing MVI before LT in HCC patients is crucial for selecting treatment options and predicting treatment efficacy. But MVI is primarily detected through immunohistochemistry and pathological analysis of postoperative tissue samples, which is invasive and limited. Moreover, HCC lesions are biologically heterogeneous. In recent years, many reports have assessed MVI preoperatively by extracting image features. PET/CT with 18F-labeled fluorodeoxyglucose (18F-FDG) as a tracer is a noninvasive method for detecting malignant tumors based on the Warburg effect and aids in assessing the histological features of tumors. 18F-FDG PET/CT has been found useful in evaluating MVI and disease-free survival (DFS) in patients with early HCC. However, the correlation between metabolic parameters of 18F-FDG PET/CT and MVI remains unknown.

Methods and Materials

Patient Selection : 162 patients with HCC were selected, of which 124 patients met the inclusion criteria as follows: Patients had to undergo 18F-FDG PET/CT before liver transplantation. Histopathological confirmation of HCC from surgical specimens was required. PET/CT images had to be clear, and clinical data had to be complete. Exclusion criteria were as follows: 18F-FDG PET/CT examination after LT; another malignancy in addition to HCC; incomplete case documentation. Clinical characteristics and pathological results of patients (including gender, age, tumor size, tumor number, tumor differentiation, T stage, and MVI grade, etc.) were retrospectively collected. This study was approved by the institutional review board, and the requirement for informed consent was waived (KY2022011).

Instruments: A GE Discovery PET/CT 710 scanner was used for imaging with specific CT scan parameters set.

Image Acquisition and Reconstruction: Imaging was performed within 60 minutes after injecting 18F-FDG, and PET images were reconstructed using an iterative algorithm.

Image Analysis: Two senior physicians reviewed and diagnosed the 18F-FDG PET/CT images, and 3D reconstructions were used to obtain metabolic parameters.

MVI Evaluation: Liver cancer tissue specimens were processed and evaluated for microvascular invasion (MVI) by experienced pathologists.

Statistical Analysis: SPSS 22 software was utilized for statistical analysis, including correlations, multivariate logistic regression, and ROC curve analysis to determine diagnostic cutoff values, AUC, sensitivity, and specificity for MVI predictors.