A NESTED CASE-CONTROL STUDY ON THE INTERACTION BETWEEN HCV AND HTLV-I IN THE DEVELOPMENT OF LIVER CANCER

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(1) Geographic Distribution of the Incidence of Adult T-cell Leukemia/lymphoma and Other Malignancies in Nagasaki Prefecture, JapanBackground: It remains unclear whether human T-cell lymphotropic virus type-I (HTLV-I) infection is associated with an increased risk of malignancies other than adult T-cell leukemia/lymphoma.Methods: The authors investigated the geographic distribution of the incidence of adult T-cell leukemia/lymphoma and other malignancies in Nagasaki Prefecture, Japan, where HTLV-I is endemic. The world age-standardized incidence rates of adult T-cell leukemia/lymphoma and five cancers of other sites were calculated in 15 areas, using the data from the Nagasaki Prefectural Cancer Registry (1985-1997).Results and Conclusions: The incidence of adult T-cell leukemia/lymphoma was found to be positively correlated with that of biliary tract cancer in men (person-years-weighted r = 0.49, P = 0.06) and liver cancer in women (r = 0.56, P = 0.03), but not with cancer of the stom … More ach, lung or cervix uteri. The results may not support the hypothesis that HTLV-I infection is strongly associated with an increased risk of cancer of the stomach, lung or cervix uteri. The significant correlation between adult T-cell leukemia/lymphoma and liver cancer may be explained by the simple coincidence of the distribution of HTLV-I and hepatitis C/B viruses, and/or the effects of HTLV-I infection to promote the progression from hepatitis C/B viral infections to chronic hepatitis, liver cirrhosis and liver cancer. The association between HTLV-I infection and cancer of the biliary tract is of concern and should be evaluated on an individual basis in future epidemiologic studies.(2) A nested case-control study of risk factors for adult T-cell leukemia/lymphoma among human T-cell lymphotropic virus type-I carriers in JapanObjectives: The purpose of this study was to investigate the serological risk factors for development of adult T-cell leukemia/lymphoma (ATL) among human T-cell lymphotropic virus type-I (HTLV-I) carriers.Methods: A nested case-control study was performed. The source population comprised 23,922 subjects who had either visited the outpatient clinic or who had received annual health check-ups at the K Hospital, Nagasaki, Japan, at least once during 1985-1996 (HTLV-I seroprevalence = 16. 1 %). Markers of HTLV-I infection were examined in stored sera from 29 incident cases of ATL diagnosed during 1985-1997, and 156 controls matched for sex, birth year, date of sample collection and HTLV-I seropositivity.Results: In exact conditional logistic regression analysis, high soluble interleukin-2 receptorlevels (>=500 U/ml) and high HTLV-I antibody titers (>=1,024) were significantly associated with an increased risk of developing ATL (Odds ratio was 26.3, 95 % confidence interval [CI] 6.0241 and 3.5, 95 % CI 1.4-9.1, respectively). The results remained essentially unchanged when the subjects were restricted to those whose histories were followed for 2 years or longer.Conclusions: These findings indicate that high soluble interleukin-2 receptor levels and high HTLV-I antibody liters are strong predictors of ATL among carriers of HTLV-I. Less