Multifactorial risk prediction analysis of liver metastasis in colorectal cancer: incorporating programmed cell death ligand 1 combined positive score and other factors

The occurrence of liver metastasis significantly impacts the prognosis of colorectal cancer. Existing research indicates that primary tumor location, vascular invasion, lymph node metastasis, and abnormal preoperative tumor markers are risk factors for colorectal cancer liver metastasis. Positive expression of PD-L1(Programmed Cell Death 1 Ligand 1) may serve as a favorable prognostic marker for nasopharyngeal and gastric cancers, where CPS(Combined Positive Score) quantifies the level of PD-L1 expression. Based on previous studies, exploring CPS as a potential risk factor for colorectal cancer liver metastasis and integrating other independent risk factors to establish a novel predictive model for colorectal cancer liver metastasis. A retrospective analysis was conducted on 437 colorectal cancer patients pathologically diagnosed at Xiangya Second Hospital, Central South University, from January 1, 2019, to December 31, 2021. Data were collected, including CPS, age, gender, primary tumor location, Ki-67 expression, pathological differentiation, neural invasion, vascular invasion, lymph node metastasis, and preoperative tumor markers.The optimal cut-off point for the continuous variable CPS was determined using the Youden index, and all CPS were dichotomized into high and low-risk groups based on this threshold (scores below the threshold were considered high-risk, and those above it were considered low-risk). Univariate logistic regression analysis was employed to identify risk factors for colorectal cancer liver metastasis, followed by the application of multivariate logistic regression analysis to integrate the selected risk factors.The predictive model established was validated through the construction of ROC (Receiver Operating Characteristic) curves, calibration curves, and DCA (Decision Curve Analysis). A nomogram was constructed for visualization purposes. The determined cut-off point for PD-L1 CPS was 4.5, with scores below this threshold indicating high risk for colorectal cancer liver metastasis. Additionally, primary tumor origin other than the rectum, presence of pericolonic lymph node metastasis, and abnormal levels of tumor markers CEA and CA199 were identified as independent risk factors for colorectal cancer liver metastasis. The constructed clinical prediction model demonstrated good predictive ability and accuracy, with an area under the ROC curve of 0.871 (95% CI 0.838-0.904). The exploration and validation of CPS as a novel predictor for colorectal cancer liver metastasis were conducted. Based on this, a new clinical prediction model for colorectal cancer liver metastasis was developed by integrating other independent risk factors. The DCA, clinical impact curve, and nomogram graph constructed based on this model have significant clinical implications and provide guidance for clinical practice.