A probe combination for detecting cancer includes one or more sets of partial hepatitis B virus (HBV) targeting probes. When sequences of each of the sets of partial HBV targeting probes are aligned, an overall sequence of the aligned set of probes matches a reference sequence of a genome of a HBV genotype or a direct repeat (DR) region on the genome. In the aligned set of probes, each of the probes overlap with one or two adjacent probes by a portion of a length of the probe. The probe combination may further includes one or more sets of hotspot gene targeting probes targeting cancer hotspot genes such as CTNNB1, TERT, and TP53 genes, one or more sets of exogenous gene targeting probes targeting portions of a lambda phage genome, and endogenous gene targeting probes targeting endogenous genes such as GAPDH and GdX genes.