Purpose: To evaluate the utility of tumor content in circulating cell-free DNA (ccfDNA) for monitoring hepatocellular carcinoma (HCC) throughout its natural history.
Methods: We included 67 hepatitis B virus (HBV)-related HCC patients, of whom 17 had paired pre- and post-treatment samples, and 90 controls. Additionally, in a prospective cohort with HBV 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 a 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), while 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, tumor content increased from 0.014 in 4 years before diagnosis to 0.026 in 1 year before diagnosis. The sensitivity of tumor content in detecting HCC increased from 22.7% (95%CI=11.5%-37.8%) within one year before diagnosis to 30.4% (95%CI=13.2%-52.9%) at 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 one year earlier than clinical diagnosis and in predicting patient prognosis.