CYP2A6 and lung cancer: However, many of these variants are specific to some populations (e.g. *4 is common in Japanese but rare in whites) and these genetic polymorphisms explain only a fraction of the variation in CYP2A6 activity (~44–64% depending on the ethnic/racial group) [9]; therefore, the phenotypic biomarker for CYP2A6 activity is expected to constitute a more suitable predictor of lung cancer risk.