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Bulky DNA adducts and risk of cancer: a meta-analysis.

We present a meta-analysis to test the hypothesis that the presence of a high level of bulky DNA adducts in tissues is associated with an increased risk of cancer in humans. Seven articles were selected that matched the selection criteria, for a total of 691 cancer patients and 632 control subjects. In five studies the cases had lung cancer, in one oral cancer, and in one bladder cancer. Six studies measured adducts in WBCs and one in normal lung tissue around tumor tissue. Six were case-control investigations, and one was a case-control study on lung cancer nested within a cohort. Current smokers showed a statistically significant difference between cases and controls, with cases having 83% higher levels of adducts than controls (95% confidence interval, 0.44-1.22). Results were negative or contradictory in ex-smokers and nonsmokers. This observation was confirmed by sensitivity analyses. Publication bias does not seem to be a problem. Despite some methodological limitations, our meta-analysis shows that current smokers with high levels of adducts have an increased risk of lung and bladder cancers. This conclusion also suggests that similar (aromatic) compounds may be involved in the etiology of both types of cancer.