Yau et al. also showed that a drop in serum AFP >20 % during the first six weeks is an exploratory early surrogate for both clinical benefit (i.e., complete response, partial response, or stable disease according to the Response Evaluation Criteria in Solid Tumors (RECIST) criteria) and PFS in advanced HCC patients receiving sorafenib [22]. The gene discussed is AFP; the disease is hepatocellular carcinoma.