Prognostic impact of the red cell distribution width in esophageal cancer patients: A systematic review and meta-analysis

AIM: To clarify the previous discrepant conclusions, we performed a meta-analysis to evaluate the prognostic value of red cell distribution width (RDW) in esophageal cancer (EC). METHODS: We searched the PubMed, EMBASE, Web of Science and Cochrane Library databases to identify clinical studies, followed by using STATA version 12.0 for statistical analysis. Studies that met the following criteria were considered eligible: (1) Studies including EC patients who underwent radical esophagectomy; (2) studies including patients with localized disease without distant metastasis; (3) studies including patients without preoperative neoadjuvant therapy; (4) studies including patients without previous antiinflammatory therapies and with available preoperative laboratory outcomes; (5) studies reporting association between the preoperative RDW and overall survival (OS)/disease-free survival (DFS)/cancer-specific survival (CSS); and (6) studies published in English. RESULTS: A total of six articles, published between 2015 and 2017, fulfilled the selection criteria in the end. Statistical analysis showed that RDW was not associated with the prognosis of EC patients, irrespective of OS/CSS [hazard ratio (HR) = 1.27, 95% confidence interval (CI): 0.97-1.57, P = 0.000] or DFS (HR = 1.42, 95%CI: 0.96-1.88, P = 0.000). Subgroup analysis indicated that elevated RDW was significantly associated with worse OS/CSS of EC patients when RDW > 13% (HR = 1.45, 95%CI: 1.13-1.76, P = 0.000), when the patient number ≤ 400 (HR = 1.45, 95%CI: 1.13-1.76, P = 0.000) and when the study type was retrospective (HR = 1.42, 95%CI : 1.16-1.69, P = 0.000). CONCLUSION: Contrary to our general understanding, this meta-analysis revealed that RDW cannot serve as an indicator of poor prognosis in patients with EC. However, it may still be a useful predictor of unfavorable prognosis using an appropriate cut-off value.