Life-style and environmental factors in the development of nasal NK/T-cell lymphoma: a case-control study in East Asia.

Cases of nasal NK/T-cell lymphoma (NKTCL) occur occasionally in Asian and Latin American countries but rarely in Western countries. The etiological role of life-style and environmental factors in nasal NKTCL was investigated. Five university hospitals in Japan and one each in Korea and China participated in this study; a total of 88 cases and 305 hospital controls were accrued during 2000-2005. The odds ratio (OR) of NKTCL obtained after adjustments of age, sex and country was 4.15 (95% confidence interval (CI), 1.74-9.87) for farmers, 2.81 (CI, 1.49-5.29) for producers of crops, 4.01 (CI, 1.99-8.09) for pesticide users, 11.65 (CI, 1.17-115.82) for residents near garbage burning plants, 2.95 (CI, 1.25-6.95) for former drinkers, and 0.49 (CI, 0.23-1.04) for current smokers. The ORs for crop producers, who minimized their exposure to pesticides by using gloves and glasses, and sprinkling downwind at the time of pesticide use, were 3.30 (95% CI, 1.28-8.54), 1.18 (95% CI, 0.11-12.13) and 2.20 (95% CI, 0.88-5.53), respectively, which were lower than those for producers who did not take these precautions. Exposure to pesticides and chemical solvents could be causative of NKTCL. Taken together, life-style and environmental factors might be risk factors for NKTCL.