Patient Baseline Characteristics
A total of 1,438 CRC patients were included in this study, and their baseline characteristics are presented in Table S1. The mean age of the patients was 58.14 ± 13.13 years. Male patients accounted for 62.7% (902 cases), while female patients accounted for 36.3% (536 cases). There were 704 (49.0%) colon cancer patients and 734 (51.0%) rectal cancer patients. According to the 8th edition of the AJCC cancer staging system, 763 patients (53.1%) were in stages I - II, and 675 patients (46.9%) were in stages III - IV. The serum ACR exhibited a wide distribution range among the patients, with a minimum value of 0.02, a maximum value of 244.20, a mean value of 8.37 ± 13.80, and a median value of 4.58. Additionally, the serum ACR also had a broad distribution, with a minimum of 6.02, a maximum of 120.86, a mean of 45.78 ± 13.81, and a median of 44.56. By plotting the ROC curve, the optimal cut - off value of ACR was determined to be 38.5 (Figure S1). Based on this, the patients were divided into a low - ACR group (ACR < 38.5, n = 902) and a high - ACR group (ACR ≥ 38.5, n = 536). Further analysis of the ACR differences among patients with different characteristics revealed that ACR was significantly correlated with the patients' gender, age, tumor location, tumor size, CEA level, and vascular invasion (all p < 0.05). The mean ACR value of deceased patients was significantly lower than that of living patients (53.8% vs 33.8%, P < 0.001). The mean ACR value of patients with recurrence was lower than that of non - recurrence patients (33.5% vs 24.9, P = 0.001). Moreover, compared with high - ACR patients, low - ACR patients had a 4 - day longer hospital stay (p < 0.001) and an additional hospital cost of 2,488.77 yuan (p < 0.001).
Comparison of composite nutritional markers
To compare the predictive abilities of ACR and other composite nutritional markers for the prognosis of CRC patients, ROC curves were plotted, and the areas under the curves (AUCs) were calculated. For 3 - year PFS, the AUC of ACR was higher than those of the NLR, PLR, and PNI (0.568 vs 0.545 vs 0.534 vs 0.557, respectively). Similarly, for 5 - year PFS, the AUC of ACR was also higher than those of NLR, PLR, and PNI (0.554 vs 0.547 vs 0.541 vs 0.559). Compared with NLR (3 - year OS, 0.565; 5 - year OS, 0.552), PLR (3 - year OS, 0.555; 5 - year OS, 0.545), and PNI (3 - year OS, 0.566; 5 - year OS, 0.560), ACR demonstrated better prognostic predictive efficacy (3 - year OS, 0.570; 5 - year OS, 0.560) (Figure S2).
Kaplan - Meier Survival Curves of Serum ACR and Prognosis
Kaplan - Meier survival analysis showed that the 5 - year PFS of patients in the high - ACR group was significantly lower than that in the low - ACR group (43.6% vs 63.3%, p < 0.001), and the 5 - year OS was also significantly lower than that in the low - ACR group (46.2% vs 73.8%, p < 0.001), as shown in Figure 1. In the subgroup analysis, for patients with TNM stages I - II, the 5 - year PFS of the low - ACR group was 57.8%, which was lower than 81.9% in the high - ACR group (p < 0.001) (Figure 2A); the 5 - year OS of the low - ACR group was 60.6%, lower than 84.9% in the high - ACR group (p < 0.001) (Figure 2B). For patients with TNM stages III - IV, the 5 - year PFS of the low - ACR group was 39.3%, lower than 56.6% in the high - ACR group (p = 0.010) (Figure 2C); the 5 - year OS of the low - ACR group was 41.8%, lower than 59.4% in the high - ACR group (p = 0.010) (Figure 2D). In the colon cancer subgroup, the 5 - year PFS of the low - ACR group was 45.1%, lower than 65.9% in the high - ACR group (p < 0.001) (Figure S3A); the 5 - year OS of the low - ACR group was 47.8%, lower than 67.4% in the high - ACR group (p < 0.001) (Figure S3B). In the rectal cancer subgroup, the 5 - year PFS of the low - ACR group was 41.9%, lower than 61.1% in the high - ACR group (p < 0.001) (Figure S4A); the 5 - year OS of the low - ACR group was 44.3%, lower than 65.1% in the high - ACR group (p < 0.001) (Figure S4B). In the CEA - normal subgroup, the 5 - year PFS of the low - ACR group was 48.8%, lower than 72.3% in the high - ACR group (p < 0.001) (Figure S5A); the 5 - year OS of the low - ACR group was 52.4%, lower than 74.8% in the high - ACR group (p < 0.001) (Figure S5B). In the CEA - elevated subgroup, the 5 - year PFS of the low - ACR group was 37.7%, lower than 48.9% in the high - ACR group (p = 0.086) (Figure S5C); the 5 - year OS of the low - ACR group was 39.1%, lower than 52.4% in the high - ACR group (p = 0.026) (Figure S5D).
Association Between ACR and Survival Outcomes
RCS analysis revealed a non - linear relationship between ACR and PFS/OS in CRC patients. As the ACR increased, the hazard ratio (HR) gradually increased. This trend was consistent across different calibration models (Figure S6). For every 1 - SD increase in ACR, the risk of PFS and OS in CRC patients was reduced by 14.0% (HR=0.860, 95% CI: 0.785–0.942, p = 0.001) and 17.8% (HR=0.822, 95% CI: 0.747–0.904, p < 0.001), respectively. Multivariate Cox regression analysis identified high ACR as an independent predictor of poor PFS (HR = 0.635, 95% CI: 0.532–0.758, p < 0.001) and OS (HR = 0.615, 95% CI: 0.512–0.738, p < 0.001). Trend test showed that a quartile analysis of ACR found that patients in the second, third, and fourth quartiles had adverse PFS rates that were 0.617, 0.556, and 0.652 times lower, respectively, than those in the first quartile (Table 1). Similarly, as the ACR increased, the HR for OS also gradually declined. The second quartile (Q2, 0.605), the third quartile (Q3, 0.555), and the fourth quartile (Q4, 0.591) led to an increased risk of adverse OS for patients (Table 2). For PFS, a multivariable forest plot revealed that ACR was an independent risk factor for the majority of patient subgroups (Figure 3A). Similarly, in most subgroups, patients with a high ACR had a relatively worse prognosis than those with a low ACR (Figure 3B).
Association Between ACR and Recurrence
Patients with CRC in the low ACR group had a higher recurrence rate than those in the high ACR group (33.5% vs 24.9%, p = 0.001). As presented in Table 3, in the adjusted model, there was a significant association between serum ACR as a continuous variable and recurrence (Per SD increment: odds ratios (ORs)=0.850, 95%CI: 0.740 - 0.980, p = 0.023). Multivariable logistic regression analysis indicated that low ACR was an independent risk factor influencing disease recurrence (OR=0.588, 95% CI: 0.439 - 0.787, p < 0.001). When serum ACR was analyzed as quartiles in the adjusted model, compared with the first quartile (Q1), participants in the second quartile (Q2, OR=0.598, 95%CI: 0.415 - 0.862, p = 0.006), the third quartile (Q3, OR=0.566, 95%CI: 0.387 - 0.827, p = 0.003), and the fourth quartile (Q4, OR=0.547, 95%CI: 0.70 - 0.809, p = 0.006) had a significantly higher risk of recurrence.
Association Between ACR and Sarcopenia
The incidence of sarcopenia was higher in CRC patients in the low ACR group than in the high ACR group (25.5% vs 15.6%, p < 0.001). Logistic regression analysis revealed that for every 1 - SD increase in ACR, the risk of sarcopenia in CRC patients was reduced by 33.7% (OR = 0.760, 95%CI = 0.650 - 0.880, p < 0.001). Low ACR was an independent risk factor affecting sarcopenia (OR=0.674. 95% CI: 0.496 - 0.917, p < 0.001). When ACR was divided into quartiles, with the increase of ACR, the prognosis of patients gradually improved. The ORs of sarcopenia were 0.853 (0.588 - 1.239), 0.528 (0.350 - 0.797), and 0.524 (0.339 - 0.810) respectively (Table 4).
Establishment of ACR - based Prediction Nomograms
In the univariate analysis, factors such as age, T stage, N stage, M stage, perineural invasion, vascular invasion, differentiation, tumor size, CEA, and ACR were closely associated with the prognosis of CRC patients. The factors with significance in the univariate analysis were incorporated into the Cox proportional - hazards regression model for multivariate analysis. The results showed that only T stage, N stage, M stage, vascular invasion, CEA, and ACR were independent prognostic factors affecting the PFS of CRC patients (Table S2). In the multivariate OS analysis, only T stage, N stage, M stage, vascular invasion, differentiation, CEA, and ACR were independent prognostic factors affecting CRC patients (Table S3). Based on the factors with statistical significance in the multivariate Cox regression analysis, a prognostic prediction model was constructed using R software, and ACR - based prediction nomograms were generated, as shown in Figure S7 and Figure S8. This nomogram assigns scores to each factor, enabling the intuitive prediction of the 1 - year, 3 - year, and 5 - year PFS and OS probabilities of patients. The prediction model was evaluated through internal validation curves, the C - index, and the ROC curve. The C - index of the PFS nomogram was 0.723, and the AUCs for 1 - year, 3 - year, and 5 - year were 0.795, 0.781, and 0.767 respectively (Figure S9A). The C - index of the OS nomogram was 0.731, and the AUCs for 1 - year, 3 - year, and 5 - year were 0.752, 0.778, and 0.768 respectively (Figure S9B). The calibration curves indicated that the predicted 1 - year, 3 - year, and 5 - year PFS and OS probabilities by the nomogram had a good consistency with the actually observed probabilities, as shown in Figure S10. The DCA demonstrated that within the 1 - 5 - year prediction interval, the ACR - based prognostic prediction model had significantly greater benefits in clinical applications than the traditional TNM staging, as shown in Figure S11. Patients were classified into high - scoring and low - scoring groups based on the median scores of the nomogram. The results showed that the high - scoring group had significantly worse PFS/OS compared to the low - scoring group (Figure S12).
To further validate the effectiveness of the model, patients were randomly divided into a validation cohort A (n = 902) and a validation cohort B (n = 536) at a ratio of 7:3 (Table S4). In validation cohort A, ACR could effectively stratify the PFS and OS of patients. The 5 - year PFS and OS of patients in the low ACR group were significantly lower than those in the high ACR group (PFS: 46.0% vs 62.4%, p = 0.001; OS: 48.8% vs 65.6%, p < 0.001) (Figure S13). In validation cohort B, it was also observed that the 5 - year PFS and OS of patients in the low ACR group were lower than those in the high ACR group (PFS: 37.8% vs 65.4%, p < 0.001; OS: 40.0% vs 67.5%, p < 0.001) (Figure S14). The C - indices of the PFS and OS nomograms in validation cohort A were 0.711 and 0.725 respectively, and those in validation cohort B were 0.750 and 0.748 respectively, all indicating good prediction accuracy. The ROC curves and calibration curves of the validation cohorts further confirmed the reliability of the model, with all AUCs > 0.75 (Figure S15). The calibration curves showed a good consistency between the predicted probabilities and the actual probabilities (Figure S16). The DCA results indicated that within the 1 - 5 - year prediction interval, the ACR - based prognostic prediction model had significantly greater benefits in clinical applications than the traditional TNM staging (Figure S17). When patients in both validation cohorts were stratified into high - scoring and low - scoring groups based on the nomogram scores, the high - scoring group consistently had worse PFS and OS outcomes, further validating the predictive power of the ACR - based nomogram (Figure S18).