The most studied cancer in the literature is lung cancer and decreased function of CYP2A6 generally associated with lower lung cancer risk [15, 16, 17, 18, 19, 20, 21],.The reason why we could not detect CYP2A6 deletion and lung cancer may be due to small sample size and that we did not consider other low active variants (see the limitation below). The gene discussed is CYP2A6; the disease is lung cancer.