Compared with smoking referents, there was a significant over-representation of the GSTM1-null genotype among patients with squamous cell carcinoma (SQ) [odds ratio (OR) = 1.7, 95% confidence interval (95%CI) = 1.1-2.7], and the NAT2-slow genotype among patients with large cell carcinoma or mixed histological diagnosis (LM) (OR = 2.5, 95%CI = 1.0-6.1).