Five variants in the SCLC group showed significant associations, but these associations were moderate (CHRNA5 rs16969968, CYP1A1 rs4646903 and NQO1 (rs1800566) and weak (GSTM1 present/null and XPC rs2228001) [32], which may point to a greater contribution of genetic predisposition in patients with NSCLC than in those with SCLC. Here, NQO1 is linked to small cell lung carcinoma.