Prognostic value of DNA methylation for bladder cancer. 
A growing number of researches manifest that DNA methylation has been considered as biomarker for the prognosis of bladder cancer (BC).  However, the results are still in a discrepancy.  This meta-analysis was conducted in accordance with PRISMA guidelines.  Studies evaluating the practicability of methylated DNA as a prognostic marker for BC were thoroughly searched via the PubMed, Web of science and the Cochrane Library databases from January 1st, 2000 to May 5th, 2018.  The association between DNA methylation and overall survival (OS) and progression-free survival (PFS) was analyzed.  Hazard ratios (HRs) or odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated to assess the correlation between methylated DNA and prognostic value in BC by using multivariate survival analysis.  Nineteen studies were included.  Patients with methylated DNA had poorer OS, compared with those with unmethylated DNA, the combined HR was 2.766 (95%CI: 2.099-3.806).  Simultaneously, methylated DNA was considerably associated with shorter PFS (HR = 2.872, 95%CI: 1.971-4.185).  Furthermore, DNA methylation had a significant association with gender (male vs female: OR = 1.486, 95% CI = 1.090-2.025), grade (3 vs 1-2: OR = 3.153, 95% CI = 2.006-4.955), tumor diameter (≤3 cm vs >3 cm: OR = 0.408, 95% CI = 0.277-0.602), number of tumors (single vs multiple: OR = 0.683, 95% CI = 0.501-0.932), stage (Ta vs T1: OR = 0.472, 95% CI = 0.342-0.654), (Ta-T1 vs T2-T4: OR = 0.338, 95% CI =0.210-0.543).  DNA methylation was negatively correlated with the prognosis of BC patients and might become a promising biomarker.