Introduction:
CDX2 methylation predicts poor prognosis in gastric cancer, squamous esophageal cancer and colorectal cancer. The present study was performed to investigate the roles of CDX2 methylation in lung cancer.

Material and methods:
One hundred and sixty-seven patients with lung cancer were enrolled. Methylation-specific PCR (MSP) was performed to investigate the methylation status of CDX2. Sequencing of the CDX2 5ʹ CpG island was conducted as well. A 5-year follow-up was performed by a research nurse or dedicated physician. A Kaplan-Meier curve was used to analyze the survival situation of patients. Univariate and multivariate Cox analysis was performed to investigate the potential predictors for prognosis of patients with lung cancer.

Results:
The patients were classified into two groups according to CDX2 status: methylation (n = 75) and unmethylation (n = 92). After the 5-year follow-up, we found that the survival rate of patients with methylation of CDX2 was much lower than in those with unmethylation of CDX2 (56% vs. 84.8%, p = 0.000). Among the smoking patients, methylation of CDX2 was associated with poorer prognosis of patients with lung cancer (p = 0.000). DFS of patients with CDX2 methylation was lower than in those without CDX2 methylation (56.0% vs. 73.9%, p = 0.009). Univariate and multivariate Cox analysis demonstrated that CDX2 methylation served as an independent prognostic predictor of patients with lung cancer (univariate: HR = 3.705, 95% CI: 1.922–7.139; multivariate: HR = 3.418, 95% CI: 1.826–6.397).

Conclusions:
CDX2 methylation may serve as an independent prognostic predictor for patients with lung cancer.