Qualification of tumour mutational burden by targeted next‐generation sequencing as a biomarker in hepatocellular carcinoma

Background & Aims Tumour mutational burden (TMB) predicts improved response and survival to immunotherapy. In this pilot study, we optimized targeted next‐generation sequencing (tNGS) to estimate TMB in hepatocellular carcinoma (HCC). Methods We sequenced 48 non‐paired samples (21 fresh‐frozen [FF] and 27 paraffin‐embedded [FFPE]), among which 11 FFPE samples were pretreated with uracil‐DNA glycosylase (UDG). Thirty samples satisfied post‐sequencing quality control. High/low TMB was defined by median number of mutations/Mb (Mut/Mb), across different minimum allele frequency (MAF) thresholds (≥0.05, ≥0.1 and ≥0.2). Results Eligible patients (n = 29) were cirrhotic (84%) with TNM stage I‐II HCC (75%). FFPE samples had higher TMB (median 958.39 vs 2.51 Mut/Mb, P