Due to the high minor allele frequency (MAF) as well as their possible involvement in an increased risk of several carcinomas [39], including lung cancer, colorectal cancer, breast cancer, leukemia, esophageal carcinoma and prostate cancer [40], CYP1A1 rs1048943 A > G and rs4646903 T > C polymorphisms are more widely studied. The gene discussed is CYP1A1; the disease is carcinoma of esophagus.