Human T-Lymphotropic Virus Type-I Infection, Survival and Cancer Risk in Southwestern Japan: A Prospective Cohort Study

Objectives: This study prospectively evaluated the associations of human T-lymphotropic virus type-I (HTLV-I) infection with survival and cancer incidence. Methods: The study base comprised 4297 adults (aged 40-69 years in 1993) who had either visited the outpatient clinic or who had received annual health check-ups at the A Hospital, Nagasaki, Japan, between 1985 and 1992 (HTLV-I seropositivity = 24.7%). During the follow-up period (1993-1999 or 2000), 290 deaths and 261 cases of malignant neoplasms occurred, including ten deaths and six incident cases of adult T-cell leukemia/lymphoma (ATL). Results: After adjustment for gender, age and other covariates, HTLV-I seropositivity was associated with an increased mortality from all-causes excluding ATL (rate ratio, RR = 1.3, 95% confidence interval, CI = 1.0-1.7), all non-neoplastic diseases (RR = 1.5, 95% CI = 1.0-2.3) and heart diseases. HTLV-I infection was not found to be associated with an increased risk of developing total cancers other than ATL (RR = 0.98, 95% CI = 0.74-1.3), colorectal cancers, liver cancer or lung cancer, but was associated with a reduced risk of gastric cancer (RR = 0.42, 95% CI = 0.17-0.99). Conclusions: HTLV-I infection is associated with increased mortality from all-causes excluding ATL and all non-neoplastic diseases. HTLV-I carriers may not be at increased general cancer risk, but at reduced risk of gastric cancer.