We thank Drs. Loomba and Ghany for their comments. As they pointed out, obesity is widely recognized as a significant risk factor for many types of human cancer, including HCC (1). In our paper, we prospectively analyzed the various clinical factors, including anti-HBc positivity, smoking, and alcohol intake, as risks for the occurrence of HCC in Japanese patients with hepatitis C virus (HCV) infection.

We found that the incidence of HCC in patients with a BMI of 30 kg/m² did not significantly differ from that of patients with a BMI of 25 kg/m² (16.7% vs. 22.1%, respectively; P = 0.85). However, the prevalence of obesity among the Japanese population is not as high as that among U.S. and European populations. In fact, only 3.0% of the HCV-positive patients analyzed in our study had a BMI greater than 30.0 kg/m². In contrast, the prevalence of obese individuals with a BMI greater than 30.0 kg/m² in the United States ranges from 13% to 27% (2). A recent U.S. study revealed that the relative risk for HCC was 1.68 times higher among women with a BMI of 35 kg/m² and 4.52 times higher among men with a similarly increased BMI than in reference groups with baseline BMIs of 18.5 kg/m² to 25.0 kg/m² (3). Thus, it seems reasonable to assume that too few Japanese patients with HCV-related chronic liver disease had BMI high enough to evaluate the risk for HCC occurrence.

Similarly, several epidemiologic data showed an increased risk for HCC among patients with diabetes, a condition closely associated with obesity (4). However, only 5.7% of our Japanese patients with HCV-related chronic liver disease had a diagnosis, with diabetes defined by the use of insulin or oral diabetic medication. Therefore, it was also difficult to analyze the statistical difference of the HCC incidence between patients with and those without diabetes enrolled in our prospective study. In conclusion, we believe that further prospective studies should be done in overweight persons to determine whether high BMI and presence of diabetes could be risks for HCC.