Generally, a strong and significant correlation between tumor tissue and autologous samples in P16INK4A promoter methylation was found across studies(Correlation coefficient 0.71, 95% CI: 0.51–0.83, P<0.0001), which suggested the higher frequency of methylation in autologous sample was found, the higher prevalence of methylation can be observed in cancer tissue in patients with NSCLC. This evidence concerns the gene CDKN2A and cancer.