GSTM1 and laryngeal carcinoma: In their studies, Li et al. [33] found no such association, Unal et al. [34] reported that GSTT1-null significantly increased in laryngeal cancer patients when compared with the non-smoking controls (p = 0.04), and Lourenço et al. [35] noted that both the GSTM1 and GSTT1 pathways are important determinants of head and neck squamous cell carcinoma in smokers.