Shallow whole-genome sequencing of circulating tumour DNA predicts clinical outcomes to systemic therapy in advanced hepatocellular carcinoma.

[BACKGROUND AND AIMS] There is an urgent need for effective prognostic biomarkers to better stratify patients with advanced hepatocellular carcinoma (HCC) undergoing systemic therapy. Shallow whole-genome sequencing (sWGS) of cell-free DNA (cfDNA) is a cost-effective approach for assessing circulating tumour DNA (ctDNA), genomic alterations, and fragmentomic patterns. This study aimed to evaluate sWGS-derived biomarkers as predictors of outcomes in advanced HCC patients receiving systemic treatment.

[METHODS] Pretreatment plasma samples from 134 patients treated with either tyrosine kinase inhibitors (TKIs; n = 83) or immune checkpoint inhibitors (ICIs; n = 51) were analysed using sWGS. Tumour fraction (TF) and copy number alterations (CNAs) were derived using ichorCNA, while DNA fragmentation was assessed using the DELFI approach. Associations with progression-free survival (PFS) and overall survival (OS) were evaluated.

[RESULTS] High TF was significantly associated with shorter median PFS (3.0 vs. 10.6 months; p<0.001) and OS (7.8 vs. 21.6 months; p=0.02). High fragmentation similarly correlated with reduced PFS (4.7 vs. 10.7 months; p<0.001) and OS (13.1 vs. 22.3 months; p<0.001). In multivariate analysis within the ICI subgroup, high fragmentation and BCLC stage independently predicted shorter PFS and OS. High AFP levels, advanced BCLC stage, and larger tumours correlated with elevated TF. Frequent CNA gains were observed in chromosomal arms 1q and 8q.

[CONCLUSION] High TF and high fragmentation levels are associated with worse clinical outcomes in advanced HCC patients treated with systemic therapy, making them promising prognostic biomarkers to consider for guiding treatment decisions.