TP53BP1 and hepatocellular carcinoma: To determine the possible mechanism and effects of regorafenib administered concurrently or sequentially with RT, further studies are clearly required, including more HCC cell lines of colony formation assays and DNA double-strand break (DSB) analysis by staining for γH2AX and/or 53BP1, to examine the effects of single and double treatment on clonogenic survival and DNA repair in additional hepatocarcinoma cell lines, in vivo tumor models, or clinical trials.