High pretreatment D-dimer level is an independent unfavorable prognostic factor of small cell lung cancer: A systematic review and meta-analysis

BACKGROUND: High pretreatment level of D-dimer in small cell lung cancer (SCLC) is commonly encountered, but the impact of high pretreatment D-dimer level on the prognosis of SCLC patients remains undetermined. Therefore, we conducted this meta-analysis focusing specifically on the prognostic value of high pretreatment D-dimer level in SCLC patients comprehensively. METHODS: We searched systematically in PubMed, Embase, and Web of Science for relevant studies published before January 28, 2019. Outcomes including 1-year overall survival (OS), progression-free survival (PFS) rates, and hazard ratios (HRs) of OS and PFS from multivariate analysis were extracted and analyzed. RESULTS: A total of 5 cohort studies consisting of 813 SCLC patients (473 patients with high pretreatment level of D-dimer and 340 with normal level of D-dimer) were finally included for meta-analysis. We found that patients with high pretreatment level of D-dimer had significantly shorter 1-year OS (47.6% vs 79.9%; fixed effects: risk ratio [RR] = 2.506; 95% confidence interval [CI] = [1.948, 3.224]; P < .001) and PFS (15.8% vs 34.0%; random effects: RR = 1.294; 95% CI = [1.060, 1.579]; P = .011) rates than those with normal level of D-dimer. Moreover, high pretreatment D-dimer level was further proved to remain as an unfavorable predictor of OS (fixed effects: HR = 1.865; 95% CI = [1.469, 2.367]; P < .001; I(2) = 7.6%) and PFS (fixed effects: HR = 1.513; 95% CI = [1.183, 1.936]; P = .001; I(2) = 0.0%) in patients with SCLC. CONCLUSION: High pretreatment level of D-dimer was found to be an independent unfavorable prognostic factor in SCLC patients. However, more studies with sufficient adjustment for confounding factors are encouraged to confirm our conclusions.