GSTM1 and head and neck squamous cell carcinoma: After stratification for ethnicity, we observed a significant association for HNSCC in European (OR = 2.01, 95% CI: 1.15–3.53, P = 0.01) and Asian (OR = 1.56, 95% CI: 1.05–2.33, P = 0.03) populations among GSTM1 and GSTT1 dual null individuals (Table 2).