Blood-based genomic profiles and 18F-fluorocholine uptake in hepatocellular carcinoma: Initial findings from an ongoing PET-based immunotherapy biomarker trial

Introduction: Aberrant Wnt/beta-catenin pathway activation has been associated with an immune-suppressed tumor phenotype and poor clinical response to immune checkpoint-targeted monoclonal antibodies in hepatocellular carcinoma (HCC). Molecular alterations involving this pathway have also been associated with increased tumor 18F-fluorocholine (FCh) uptake (ITFChU), supporting the scientific premise of an ongoing NCI-funded phase 2 clinical trial to evaluate 18F-FCh PET/CT and cell-free DNA based genomic profiling as sources of tumor biomarkers for predicting response to immune checkpoint inhibitor monoclonal antibody-based treatment of advanced unresectable HCC (NCT04965454).

Methods: In this first interim analysis of NCT04965454, liquid biopsy gene mutation profiles and 18F-FCh PET/CT findings from patients with advanced unresectable HCC were compared and examined in the context of NCT01395030, a previously completed diagnostic clinical trial conducted in early-stage HCC that involved whole-transcriptome analysis of resected tumor tissue and radiogenomic correspondence with 18F-FCh PET/CT.

Results: Of the first 5 HCC patients enrolled to NCT04965454, 18F-FCh PET/CT demonstrated ITFChU in 4. In each patient with ITFChU, blood-based genomic profiling revealed one or more gene mutations (CTNNB1 in 3, ARID1A in 2, LKB1 in 1) previously implicated in the reduction of anti-tumor immune cell responses, along with concomitant mutations involving TERT and TP53. Pathway analysis further tied these molecular alterations with dysregulated structural lipid metabolism. In contrast, no such mutations were identified in the liquid biopsy profile of the patient without ITFChU. In this latter patient, increased tumor FDG uptake discordant with FCh uptake was also observed on FDG PET/CT. Blood-based tumor mutation burden estimates in all patients were relatively low, ranging from 3 to 13 (median 5) mutations/Mb. Furthermore, evidence of microsatellite instability was not detected in any liquid biopsy sample. Transcriptomic analysis and targeted sequencing involving tumor samples obtained from NCT01395030 also associated ITFChU with CTNNB1 mutations and HCC molecular sub-types associated with aberrant Wnt/beta-catenin activation and immunosuppressive tumor microenvironment, including the Hoshida S3 sub-type, the Chiang CTNNB1-activation sub-type, and Boyault G5/G6 sub-types.

Conclusions: Findings from initial interim analysis of data collected by NCT04965454 are compatible with its scientific premise based on previously observed associations between immunogenomic and radiogenomic profiles. Study recruitment will continue for NCT04965454 and all patients enrolled to date have started treatment with immune checkpoint inhibitor antibody-based regimens for advanced unresectable HCC. As the trial continues, liquid biopsy and imaging data collected before and early in the course of immunotherapy treatment will be evaluated as potential predictive biomarkers of objective response.