Association between preoperative anemia and postoperative short-term outcomes in patients undergoing colorectal cancer surgery - a propensity score matched retrospective cohort study

Background Based on previous studies which failed to analyze important confounding variables, the association between preoperative anemia and outcomes of patients who underwent colorectal cancer (CRC) surgery has not been clearly demonstrated. This study aimed to investigate the relationship between preoperative anemia and shortterm outcomes in patients with CRC. Methods Data from a retrospective collective database of patients who underwent CRC surgery at our hospital between September 1, 2019 and September 30, 2021 were retrieved and analyzed, and the short-term postoperative outcomes of anemic (hemoglobin < 120 g dL(- 1) for female, hemoglobin < 130 g dL(- 1) for male) and non-anemic patients were analyzed, using a 1:1 propensity score matching (PSM) analysis. Results After excluding some cases, the remaining 1894 patients had complete data available for analysis. The incidence of preoperative anemia was 39.8% (754/1894). Before PSM, preoperative anemia patients had a higher risk of major morbidity than non-anemia patients (27.2% vs. 23.1%, odds ratio [OR] 1.245, 95% confidence interval [CI] 1.008-1.538, P = 0.042). After PSM was performed in the cohort, 609 patients remained in the anemic and non-anemic groups. The incidence of major morbidity (25.8% vs. 24.0%, OR 1.102, 95% CI 0.849-1.429, P = 0.446) between anemic and non-anemic patients was comparable. No significant difference was found between the anemic and non-anemic groups in postoperative length of stay (8.0 [6.0-12.0] vs. 8.0 [7.0-11.0], P = 0.311). The sensitivity analysis results were in accordance with the primary outcome. Furthermore, we did not ascertain any discernible correlation between the extent of anemia and significant major morbidity. Conclusions Compared with preoperative non-anemia, anemia status does not seem to be associated with major morbidity in patients with CRC surgery. It is noteworthy that, anemia is insufficient as a solitary risk factor and may be a better marker of poor health resulting from multiple factors.