Monitoring Hepatocellular Carcinoma Using Tumor Content in Circulating Cell-Free DNA

Purpose: The objective of the study was to evaluate the use of tumor content in circulating cell-free DNA (ccfDNA) for monitoring hepatocellular carcinoma (HCC) throughout its natural history. Experimental Design: We included 67 patients with hepatitis B virus-related HCC, of whom 17 had paired pre- and posttreatment samples, and 90 controls. Additionally, in a prospective cohort with hepatitis B virus surface antigen-positive participants recruited in 2012 and followed up biannually with blood sample collections until 2019, we included 270 repeated samples before diagnosis from 63 participants who later developed HCC (pre-HCC samples). Shallow whole-genome sequencing and the ichorCNA method were used to analyze genome-wide copy number and tumor content in ccfDNA. Results: High tumor content was associated with advanced tumor stage (P < 0.001) and poor survival after HCC diagnosis [HR = 12.35; 95% confidence interval (CI) = 1.413-107.9; P = 0.023]. Tumor content turned negative after surgery (P = 0.027), whereas it remained positive after transarterial chemoembolization treatment (P = 0.578). In non-HCC samples, the mean tumor content (+/- SD) was 0.011 (+/- 0.007) and had a specificity of 97.8% (95% CI = 92.2%-99.7%). In pre-HCC samples, the tumor content increased from 0.014 at 4 years before diagnosis to 0.026 at 1 year before diagnosis. The sensitivity of tumor content in detecting HCC increased from 22.7% (95% CI = 11.5%-37.8%) within 1 year before diagnosis to 30.4% (95% CI = 13.2%-52.9%) at the Barcelona Clinic Liver Cancer (BCLC) stage 0/A, 81.8% (95% CI = 59.7%-94.8%) at stage B, and 95.5% (95% CI = 77.2%-99.9%) at stage C. Conclusions: The tumor content in ccfDNA is correlated with tumor burden and may help in monitoring HCC 1 yearearlier than clinical diagnosis and in predicting patient prognosis.