HCV infection (HCV+) status was defined as positive for HCV RNA. Non-B, non-C status was defined as negative for HBsAg and not having a high titer of anti-HBc Ab (HBV−) as well as negative for HCV RNA (HCV−). Radiation dose to the liver was estimated for each subject according to Dosimetry System DS02.30 A weighted sum of the gamma dose in gray plus 10 times the neutron dose

in gray was used. Because of the countermatched selection of cases, direct comparison of doses between cases and controls selleckchem in the study requires that control doses be weighted by the inverses of their selection probabilities. Information on alcohol consumption was obtained from the 1965 AHS questionnaire when available, with missing data complemented using the 1978 mail survey. Alcohol consumption was quantified as volume of each type of alcoholic beverage; mean ethanol amounts were calculated as grams per day Selleck Cilomilast as described.31 BMI (kg/m2) was calculated from height and weight measured at the AHS examination. Subjects were classified based on BMI quintiles with cutpoints of 19.5, 21.2, 22.9, and 25.0. Following the recommendations for Asian people by the World Health Organization (WHO), the International Association for the Study of Obesity, and the International obesity Task Force,32 21.3 to 22.9 kg/m2 was considered normal,

23.0 to 25.0 kg/m2 as overweight, and >25.0 kg/m2 as obese. We used information on BMI obtained 10 years before the time of HCC diagnosis or control matching because this condition is subject to change due to disease progression in the later stages before development of HCC. Information 上海皓元 on smoking habit was obtained from the 1965 questionnaire; subjects were categorized as never, current

(at time of survey), or former smoker. This study (RERF Research Protocol 1-04) was reviewed and approved by the Research Protocol Review Committee and the Human Investigation Committee of RERF. The nested case-control design was analyzed using a partial likelihood method analogous to that used for cohort follow-up studies,33 which is in practice the same as the conditional binary data likelihood for matched case-control studies34 except that the subjects (cases and “controls”) in the study are not completely independent due to repeated selection. Cumulative incidence of HCC by follow-up time (year) and age was derived according to the method of Nelson and Aalen, using Cox regression to adjust for age at start of follow-up. Cumulative incidence by radiation dose groups (0-0.0009, 0.001-0.999, and 1.0+ Gray) was compared using the Gehan/Breslow generalized Wilcoxon test. All factors other than radiation were analyzed using relative risks (RRs) estimated by a log-linear model.