We evaluated the interaction between hepatitis C virus (HCV) and cigarette smoking on death from hepatocellular cancer in The Japan Collaborative Cohort Study. The odds ratio of death from HCC for smoking was 9.60 (1. 50 -61.35) Many studies have reported that chronic hepatitis C virus (HCV) infection is a risk factor for hepatocellular carcinoma (HCC) (Mori et al, 2000;El-Serag, 2002;Sun et al, 2003;Ayoola and Gadour, 2004), HCV appearing to be more hepatocarcinogenic than hepatitis B virus (HBV) (Pang et al, 2005). While alcohol is a well established risk factor for HCC, there is evidence that cigarette smoking is also a risk factor (Mukaiya et al, 1998;Mizoue et al, 2000;Chen et al, 2003), though some studies reported no or an insignificant association (La Vecchia et al, 1988;Evans et al, 2002). Recently, an association between diabetes mellitus and HCC (or HCV) has been reported (Caronia et al, 1999;Toyoda et al, 2001). We evaluated the interaction between HCV infection and cigarette smoking by means of a nested case -control study from a large cohort.
MATERIALS AND METHODSThe Japan Collaborative Cohort Study (JACC Study) for Evaluation of Cancer Risk sponsored by the Ministry of Education, Science, Sports and Culture of Japan (Monbusho) is a large prospective cohort study, which was mounted from 1988 to 1990 in 45 areas in Japan. The number of subjects is 110 792 (46 465 males and 64 327 females) who were 40 -79 years of age at the time of the baseline survey. Individual informed consent to participate in the study was obtained in 36 out of 45 areas . The subjects were asked to complete a self-administered questionnaire about past medical history, various life style factors and marital status as baseline information. The detailed design of the JACC study has been described previously (Ohno and Tamakoshi, 2001;Watanabe et al, 2005). During the approximately 10 years of follow-up through December 31, 1999, there were 550 deaths from liver cancer that were coded as C22 in the International Classification of Diseases and Related Health Problems, 10th Revision. Those survey participants who underwent healthscreening checks sponsored by municipalities were asked to donate blood samples during the same period as the questionnaire survey. Eventually, 39 242 subjects provided blood samples . Baseline serum samples had been collected 120 of the 550 subjects who died of liver cancer. As the control group, sera of 11 543 subjects from the same geographical areas as the 120 deaths also were screened for anti-HCV. Deaths (nine) coded as C22.9 (liver cancer not otherwise specified) were excluded from this analysis, while deaths (five) coded as C22.1 (intrahepatic cholangiocarcinoma and cholangiohepatoma; included among non-HCC deaths), leaving 106 deaths from HCC that were regarded as the end point of this analysis. The total subjects were 11 654 but as the sera of 34 cases and controls could not be screened because of insufficient serum volume, the sera of 11 620 subjects were screened for antibody to HCV (anti-HCV) an...