Residual tumors and early recurrence/metastasis after radiotherapy (RT) compromise the patient survival with hepatocellular carcinoma (HCC). Timely detecting residual/recurrence/metastasis and the clonality is required to implement salvage therapies properly. The major unmet needs of radiotherapy to HCC are the difficulties in early evaluating response by images and timely detection of intrahepatic recurrence and extrahepatic metastasis. Thus, an accurate and personalized biomarker for response prediction and disease monitoring is demanded. Cell-free tumor-specific DNA (ctDNA) has garnered attention as a promising biomarker in cancer patients. However, in HCC, the detection rate is low (9-21.2%), mainly due to the limited prevalence of traditional somatic mutations and the difficult separation of ctDNA fragments from normal cells. The investigators aim to develop a novel ctDNA, the virus-host chimera DNA (vh-DNA), as a biomarker for hepatitis B virus (HBV)-related HCC patients undergoing RT. HBV vh-DNA presents in \~90% of HBV-related HCC patients and can be differentiated from DNA released from the normal cells through enrichment by capturing with HBV probes. vh-DNA might be advantageous to the traditional somatic mutation type of ctDNA. The investigators hypothesize that HBV vh-DNA could accurately diagnose residual tumor by 6-12 months earlier than contemporary images and predict early recurrence/metastatsis, thus allows early intervention of salvage therapies.
The investigators will first use our previously collected serum samples and surgical/biopsied tissues from HBV-related HCC patients undergoing radiotherapy. The consistency of junctional clones by Capture NGS needs to be tested between both pre- and post-RT serums, and serial changes in copy numbers of vh-DNA by ddPCR are quantified in the representative cases. The same junction clones from pre-post-RT serums and surgical tissues will be confirmed and the copy number changes of vh-DNA be correlated with RT response and disease-control status.
The investigators plan to identify HBV integrations by Capture NGS and quantify the specific vh-DNA by ddPCR as personalized biomarkers from the same-patient serum samples. The investigators will further correlate clinical response and recurrence/metastasis with serial changes of vh-DNA copy numbers. The investigators have been prospectively collecting plasma samples from HBV-related HCC patients before/after RT, at 1, 4, 7 months, and at recurrence/metastasis. The investigators plan to confirm the viable role of pre-/post-RT changes of plasma vh-DNA copies of the same junction clone in post-RT response and prognosis. Moreover, The investigators will explore the recurrent/metastatic tumors arising from the original or a de novo one by identifying their clonality with HBV integration patterns. The true value of this novel HBV chimera vh-DNA will be revealed. The results will also support the consolidative use of personalized vh-DNA for earlier evaluating treatment response after RT, for post-RT disease monitoring, and for differentiating clonality at recurrence to design future clinical trial on combinational treatment.
