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Why some smokers do not get lung cancer and some nonsmokers do remains unclear. Environmental tobacco smoke (ETS) is one factor known to increase the risk in nonsmokers. Mutations in genes that code for enzymes that detoxify carcinogens may potentiate risk. The genes for one of these enzymes, glutathione S-transferase, have a "null" allele inactivated by a deletion of DNA coding sequences. This variant occurs in about 50% of the white women and men in the United States. These investigators studied 106 white, nonsmoking women with lung cancer.
Among 51 women with ETS exposure, the odds ratio for lung cancer was 2.6 (95% CI, 1.1 to 6.1), favoring excess "null" alleles. In the 55 women without ETS exposure, the genotype was evenly distributed. …