18f-fdg-pet for assessing biological viability and prognosis in liver transplant patients with hepatocellular carcinoma

Liver transplantation (LT) has become standard of care in patients with non-resectable early stage hepatocellular carcinoma (HCC) in liver cirrhosis. Currently, patient selection for LT is strictly based on tumor size and number, provided by the Milan criteria. This may, however, exclude patients with advanced tumor load but favourable biology from a possibly curative treatment option. It became clear in recent years that biological tumor viability rather than tumor macromor-phology determines posttransplant outcome. In particular, microvascular invasion and poor grading reflect tumor ag-gressiveness and promote the risk of tumor relapse. Pretrans-plant biopsy is not applicable due to tumor heterogeneity and risk of tumor cell seeding.18F-fludeoxyglucose (18F-FDG) positron emission tomography (PET), an established nuclear imaging device in oncology, was demonstrated to non-invasively correlate with unfavorable histopathologic fea-tures. Currently, there is an increasing amount of evidence that18F-FDG-PET is very useful for identifying eligible liver transplant patients with HCC beyond standard criteria but less aggressive tumor properties. In order to safely expand the HCC selection criteria and the pool of eligible liver recipients, tumor evaluation with18F-FDG-PET should be implemented in pretransplant decision process.