RESUMEN
Background: Gastric cancer (GaC) is the second cause of death by cancer in the world and one of the first causes in Chile. However, the burden of this disease shows remarkable worldwide variation probably explained by environmental and genetic factors. The role of susceptibility low penetrance genes and environmental and dietary factors in the etiology of gastric cancer is not well-known. Aim: To analyze the possible association between CaG susceptibility, genetic (CYP1A1 and GSTM1 polymorphisms) and environmental (tobacco and alcohol) factors. Patients and Methods: In a case-control study, we included 73 patients with a pathologically diagnosed GaC and 263 controls. DNA was extracted from peripheral blood to detect allele variants for CYP1A1 and GSTM1, using polymerase chain reactions and digestion with restriction enzymes. Results: There was a clear association of smoking and alcohol ingestion with GaC with odds ratios (OR) of 2.54 (95 percent confidence intervals (CI) of 1.45-4.46 and OR of 3.36 (95 percent CI 1.76-6.41), respectively. Polymorphic variants of CYP1A1 and GSTM1 had no association with GaC. However, the m2 variant of CYP1A1 significantly modifies the risk induced by tobacco or alcohol (OR 13.65; 95 percent CI 3.15-59.05 y 8.37; 95 percent CI 1.86-37.64, respectively). Conclusions: Subjects that carry the m2 allelic variant of CYP1A1 and are exposed to tobacco smoke or alcohol have a significantly higher risk of developing gastric cancer.