Preoperative anemia and long-term survival in patients undergoing colorectal cancer surgery: a retrospective cohort study

Abstract

Background: The impact of preoperative anemia on a survival outcome and the importance of correcting preoperative anemia in patients with colorectal cancer (CRC) remain controversial. This study aimed to explore how preoperative anemia affects the long-term survival of patients undergoing colorectal cancer surgery.

Methods: This was a retrospective cohort study in which adult patients underwent surgical resection for colorectal cancer between January 1, 2008, and December 31, 2014, at a large tertiary cancer center. A total of 7436 patients were enrolled in this study. Anemia was defined according to the diagnostic criteria of China (hemoglobin level < 110 g/L for women and < 120 g/L for men). The median follow-up time was 120.5 months (10.0 years). Inverse probability of treatment weighting (IPTW) using the propensity score was used to reduce selection bias. Overall survival (OS) and disease-free survival (DFS) were compared between patients with and without preoperative anemia using the Kaplan-Meier estimator and the weighted log-rank test based on IPTW. Univariate and multivariate Cox proportional hazards models were used to assess factors associated with OS and DFS. Multivariable Cox regression was also used to assess red blood cell (RBC) transfusion associations between preoperative anemia and outcomes.

Results: After IPTW adjustment, clinical profiles were similar, except that tumor location and TNM stage remained imbalanced between the preoperative anemia and preoperative non-anemia groups (p < 0.001). IPTW analysis showed that the 5-year OS rate (71.3 vs. 78.6%, p < 0.001) and the 5-year DFS rate (63.9 vs. 70.9%, p < 0.001) were significantly lower in the preoperative anemia group. Multivariate analysis showed that preoperative anemia was associated with poorer OS and DFS, while RBC transfusion may improve OS (hazard ratio [HR] 0.54, p = 0.054) and DFS (HR 0.50, p = 0.020) in CRC patients with preoperative anemia.

Conclusions: Preoperative anemia is an independent risk factor for survival in patients undergoing colorectal surgery. Strategies to reduce preoperative anemia in patients with CRC should be considered.

Keywords: Anemia; Colorectal cancer; Disease-free survival; Overall survival; Surgery.

Fig. 1

Postoperative recovery outcomes after weighting. A The length of postoperative hospitalization had no significant differences between preoperative anemia and non-anemia groups (median time 9.5 vs. 9.5 days, p = 0.275). B The patients in the preoperative anemia group more likely had postoperative anemia (89.3 vs. 18.6%, p < 0.001) and higher mortality (31.2 vs. 23.7%, p < 0.001), but similar on 30-day readmission rates (3.7 vs. 3.2%, p = 0.262). *p < 0.001

Fig. 2

Overall survival (OS) and disease-free survival (DFS) after weighting by the Kaplan–Meier method. A The 5-year OS rate was significantly worse in the preoperative anemia group than in the non-anemia group (71.3% vs. 78.6%, p < 0.001). B The preoperative anemia was also associated with a significantly worse 5-year DFS (63.9% vs. 70.9%, p < 0.001)

Fig. 3

Overall survival (OS) and disease-free survival (DFS) after weighting by the Kaplan–Meier method when pre- and post-operative anemia were both considered. A When preoperative and postoperative anemia were both considered, the 5-year OS rates were 71.5%, 70.0%, 73.9%, and 79.6% in the combined preoperative and postoperative anemia, preoperative but not postoperative anemia, postoperative but not preoperative anemia and non-anemia groups, respectively (p < 0.001). B When preoperative and postoperative anemia were both considered, the 5-year DFS rates were 64.1%, 62.6%, 64.6%, and 72.3%, respectively, in these four groups (p < 0.001)

Fig. 4

The interaction between preoperative anemia and perioperative blood transfusion after weighting. A, C When non-transfusion was the stratified variable, the preoperative anemia group has poorer overall survival (OS) and disease-free survival (DFS) than the preoperative non-anemia group; B, D When blood transfusion was the stratified variable, the preoperative anemia group has a better outcome in most follow-up, especially for DFS