Long-term prognostic value of preoperative anemia in patients with colorectal cancer: A systematic review and meta-analysis

Objective: To evaluate the long-term prognostic factor of preoperative anemia in colorectal cancer patients. Background: Anemia is frequently observed in colorectal cancer patients, with a case incidence of 30 to 67 percent. Besides an indicator of tumor-induced blood loss and inflammation, anemia in cancer is also suggested to be a cause of inferior outcome, possibly via worsening of tumor hypoxia. As surgery is likely to enhance anemia, the long-term prognostic value of preoperative anemia seems most interesting. Methods: Comprehensive searches were carried out in all relevant databases, including MEDLINE, Embase and Web-of-Science. To include studies addressing overall survival, follow-up had to be at least 24 months or till death. For pooling of survival results, a mixed-linear (fixed-effects) model was fit to the reported hazard ratios (HRs) to calculate a pooled estimate and confidence interval. Results: We included 12 studies comprising 3588 patients to estimate the association between preoperative anemia and overall survival (OS) and disease-free survival (DFS). In a fixed-effects meta-analysis of eight studies, including both colon and rectal cancer, preoperative anemia was significantly associated with poor OS (HR 1.56; 95% CI 1.30 to 1.88; p < 0.001). A meta-analysis of seven studies also showed that preoperative anemia was significantly associated with poor DFS (HR 1.34; 95% CI 1.11 to 1.61; p =0.002). Restricted to studies exclusively on colon cancer or rectal cancer, HRs for OS were 1.25 (95% CI 1.00 to 1.55; p = 0.05) and 2.59 (95% CI 1.68 to 4.01; p < 0.001), respectively, while HRs for DFS were 1.21 (95% CI 0.96 to 1.52; p = 0.11) and 1.61 (95% CI 1.18 to 2.21; p = 0.003). Conclusion: The present meta-analysis reveals that preoperative anemia is significantly associated with decreased long-term OS and DFS in rectal cancer, but not in colon cancer patients, although this metaanalysis is mainly based on retrospective studies with high heterogeneity. These results justify raised awareness about the impact of preoperative anemia on long-term survival. (C) 2017 Elsevier Ltd. All rights reserved.