RARB and non-small cell lung carcinoma: The subgroup analysis by ethnicity regarding the methylation of P16, RASSF1A, APC, and RARβ genes showed that the methylation of the P16 and RARβ genes was associated with the occurrence of NSCLC in the Asian and Caucasian populations with, suggesting that the methylation of P16 and RARβ genes can be used as biomarkers for NSCLC detection in both ethnical groups.