Abstract
Background/Objectives: Systemic inflammatory markers are increasingly recognized as prognostic indicators in metastatic colorectal cancer (mCRC), demonstrating significant associations with survival outcomes. The aim of this study was to evaluate the prognostic value of the Aarhus composite biomarker score (ACBS) in patients with metastatic colorectal cancer and to introduce the modified ACBS as a laboratory-based prognostic tool in mCRC. Methods: The Aarhus Composite Biomarker Score was calculated using serum albumin, C-reactive protein (CRP), neutrophil count, lymphocyte count, and hemoglobin levels. The modified Aarhus Composite Biomarker Score-1 (mACBS-1) stratified patients into three prognostic groups: favorable, intermediate, and poor risk. The simplified modified Aarhus Composite Biomarker Score-2 (mACBS-2) categorized patients into two prognostic groups (low vs. high risk). Survival analyses were performed using the Kaplan–Meier method, and prognostic factors were evaluated using Cox regression analysis. Results: The median overall survival (OS) was 35 months (95% CI: 29.38–40.62). Stratification by mACBS-1 revealed median OS values of 47, 30, and 14 months for favorable-, intermediate-, and poor-risk groups, respectively (p = 0.002). Similarly, mACBS-2 distinguished two prognostic groups, with median OS of 47 months in the favorable-risk group and 30 months in the poor-risk group (p = 0.001). In multivariable analysis, ACBS remained an independent predictor of overall survival, with three abnormal biomarkers conferring a significantly increased mortality risk (HR 4.61, 95% CI 2.17–9.82, p < 0.001). Similarly, poor-risk classification by mACBS-1 (HR 3.36, 95% CI 1.58–7.12, p = 0.002) and mACBS-2 (HR 2.05, 95% CI 1.29–3.26, p = 0.002) was independently associated with worse survival. Conclusions: The ACBS and its modified versions (mACBS-1 and mACBS-2) are simple, laboratory-based prognostic tools with independent predictive value for survival in metastatic colorectal cancer. Its clinical use may support improved risk stratification and individualized patient management.