HBV-host cfDNA as Minimal Residual Tumor Marker for HBV-related HCC

Early stage HCC is treated by curative surgical resection or by local ablation (such as radio-frequency) as the current standard of care. The complete removal of clinical visible HCC is then confirmed by imaging by MRI or CT, or by a decline of tumor marker (AFP or PIVKA). However, despite an apparent complete removal of the HCC, those post-curative patients frequently develop tumor recurrence at a rate ranging 10-50% within the first year. The high rate of early HCC recurrence indicated a minimal residual HCC after the curative therapies in a significant proportion of patients. A better and more specific biomarker for detecting the residual HCC will improve the patients' prognosis prediction and therapeutic plan. To detect the minimal residual HCC, a biomarker unique to the tumor is needed. Currently, the cell-free circulating DNA carrying tumor-specific somatic mutations has been advocated as a promising one. It has been applied to investigate the tumor responses or resistances to cancer therapy. However, currently it is restricted to detect or follow only large advanced cancer, because of the difficulty in separating or enriching the cfDNA with tumor-specific mutations from the cfDNA from normal cells. In this project, the investigators proposed that one class of somatic mutation in HBV-related HCC, namely the insertion mutagenesis by integrated HBV DNA, could be adopted to circumvent this difficulty. HBV DNA integration has been found in the chromosomes of about 90% of HBV-related HCC and the integration site is unique to individual HCC. The HBV-host junction DNA fragment from one HCC is therefore a tumor-specific biomarker. Such fragments can be released into the circulation as cell-free circulating DNAs, and the detection of the HBV-host chimera DNAs in the circulation is a reliable evidence for the presence of the tumor in the patient. Therefore the cf circulating HBV-host chimera DNA is proposed to assay any minimal residual HCC after curative therapies.