Then, 57 articles excluded with reasons (one mixed oral precancerous and cancer cases, one had no control group, two reviews, four reported CYP1A1 expression, two didn’t report the prevalence of alleles and genotypes, one book chapter, twenty-two reported other polymorphisms of CYP1A1, two reported duplicate publications, one family-based study, one had no sufficient data, one reported oral precancerous cases, twelve studies reported less than 100 cases in one or two groups (case and control groups), and seven meta-analyses). This evidence concerns the gene CYP1A1 and cancer.