The GSTM1null genotype is associated with a small increased lung cancer risk when compared to controls
with at least one copy of the GSTM1gene. As two copies of the GSTM1gene might provide more protection
than a single copy, we have determined GSTM1 copy number in a lung cancer case-control study. Cases
with incident lung cancer were identified through a Bronchoscopy Unit and two separate hospital based
control groups with non-malignant disease were selected with one from the same Bronchoscopy Unit
and the other from a chest clinic at the same hospital. Subjects with at least one GSTM1 copy had a
decreased lung cancer risk whatever the control group: the odds ratio (95% CI), after adjustment for age,
gender and smoking duration, was 0.64 (0.41–0.98) and 0.54 (0.32–0.91) with bronchoscopy and chest
clinic controls, respectively. Lung cancer risk varied with GSTM1 copy number with chest clinic controls
only: the ORwas 0.56 (0.32–0.97) for one copy of the GSTM1 gene and with two copies 0.43 (0.15–1.22), a
trend that was significant (p = 0.02): with bronchoscopy controls the trend was not significant (p = 0.07).
Results then confirm that the presence of GSTM1 provides protection against the risk of lung cancer. In
addition there is equivocal evidence that this protection varies with the number of gene copies.