Patients’ characteristics
A total of 639 (colon cancer in 460 cases and rectal cancer in 179 cases) patients were enrolled in this study. Severe POCs of CDC grade ≥III were observed in 102 patients (16.0%). According to the ROC curve analysis, patients were divided into two groups based on the cut-off value of the SAS. The patients with an SAS ≤6 (n=190, 29.7%) were assigned to the low-SAS group, and those with an SAS ≥7 (n=449, 70.3%) were assigned to the high-SAS group.
Clinicopathological characteristics of the high- and low-SAS groups
The low-SAS group more frequently included patients with GPS ≥1 (p<0.001), advanced pT (p=0.003), advanced pStage (p=0.005), histologically undifferentiated tumor type (p=0.03), open surgery (p<0.001), larger EBL (p<0.001), longer operative time (p=0.023) and transfusion (p<0.001) than the high-SAS group (Table 2).
Postoperative outcomes
The low-SAS group more frequently included patients with severe POCs (CDC grade ≥III) (p<0.001) and who had a significantly longer postoperative stay (p<0.001) than the high-SAS group (Table 2).
The prognosis
The median follow-up time was 63.4 (IQR, 54.8−83.0) months for all patients. Recurrence was observed in 96 cases (15.0%). Death due to CRC was observed in 61 cases (9.5%). A total of 142 deaths (22.2%) were observed. The 5-year OS, RFS and CSS rates for the entire study population were 82.4%, 86.1% and 91.8%, respectively. Kaplan-Meier survival curves comparing the OS, RFS and CSS between the two groups are shown in Figure 1A-C. The OS, RFS and CSS rates in the low-SAS group were significantly lower than those in the high-SAS group (p<0.001, p=0.003, and p<0.001, respectively).
Univariate and multivariate analyses for the OS and CSS
The results of univariate and multivariate analyses for the OS and CSS are summarized in Tables 3. In the univariate analyses for the OS, age ≥75 years old (p<0.001), CCI ≥1 (p<0.001), GPS ≥1 (p<0.001), ASA-PS ≥3 (p<0.001), open surgery (p<0.001), SAS ≤6 (p<0.001), histologically undifferentiated tumor type (p<0.001), pStage ⅠⅠⅠ (p=0.001) and severe POCs (p=0.01) were significantly associated with a worse OS. In the multivariate analysis for the OS using variables with p<0.1 in univariate analyses, age ≥75 years old (HR, 2.55; 95% CI, 1.79–3.64; p<0.001), CCI ≥1 (HR, 1.58; 95% CI, 1.09–2.30; p=0.015), ASA-PS ≥3 (HR, 3.00; 95% CI, 1.99–4.49; p<0.001), SAS ≤6 (HR, 1.51; 95% CI, 1.04–2.17; p=0.03), histologically undifferentiated tumor type (HR, 2.86; 95% CI, 1.58–4.86; p<0.001) and pStage III (HR, 1.90; 95% CI, 1.33–2.69; p<0.001) were identified as independent prognostic factors for the OS. In contrast, in the univariate analyses for the CSS, open surgery (p=0.001), SAS ≤6 (p<0.001), rectal cancer (p=0.016), histologically undifferentiated tumor type (p<0.001), pStage ⅠⅠⅠ (p <0.001), severe POCs (p=0.029) and adjuvant chemotherapy (p<0.001) were significantly associated with a worse CSS. In the multivariate analysis for the CSS using variables with p<0.1 in univariate analyses, SAS ≤6 (HR, 1.88; 95% CI, 1.07–3.30; p=0.028) and pStage III (HR, 5.85; 95% CI, 2.88–12.1; p<0.001) were identified as independent prognostic factors for the CSS.
Subgroup analyses
A subgroup analysis according to the presence of severe POCs was conducted. The Kaplan-Meier survival curves comparing the OS based on the SAS in patients with and without severe POCs are shown in Figure 2A, 2B. The OS rates in the low-SAS group were significantly lower than those in the high-SAS group among the patients with and without severe POCs (p=0.02 and p=0.016 respectively). A subgroup analysis according to the pStage (I, II and III) was also conducted. The Kaplan-Meier survival curves comparing the OS based on the SAS in patients with pStage I, II and III disease are shown in Figure 3A−C. The OS rates in the low-SAS group were significantly lower than those in the high-SAS group among patients with pStage II and III disease (p=0.048 and p=0.016 respectively), while no significant difference was seen among the patients with pStage I disease (p=0.172).