Predictive value of indirect bilirubin before neoadjuvant chemoradiotherapy in evaluating prognosis of local advanced rectal cancer patients

BACKGROUND: Many biomarkers have predictive value for overall survival (OS) and disease-free survival (DFS) in tumor patients. However, the role of indirect bilirubin (IBIL) in local advanced rectal cancer (LARC) patients treated with neoadjuvant chemoradiotherapy (nCRT) has not been studied. AIM: To explore the predictive value of IBIL before nCRT (pre-IBIL) for the OS and DFS of LARC patients treated with nCRT. METHODS: A total of 324 LARC patients undergoing nCRT with total mesorectal excision (TME) were enrolled. Preoperative clinical features and postoperative pathological characteristics were collected. Cox regression analysis was performed, and a Cox-based nomogram was developed to predict OS and DFS. We also assessed the predictive performance of the nomogram with calibration plots and receiver operating characteristic (ROC) curves. RESULTS: Among 324 patients, the median pre-IBIL was 6.2 μmol/L (interquartile range: 4.6 μmol/L-8.4 μmol/L). In the Cox multivariate regression analysis, we found that pre-IBIL, smoking history, tumor regression grade (TRG), vascular invasion, and carbohydrate antigen 19-9 before nCRT (pre-CA19-9) were predictors of OS. Additionally, pre-IBIL, body mass index (BMI), nCRT with surgery interval, TRG, and vascular invasion were predictors of DFS. Predictive nomograms were developed to predict 5-year OS and 5-year DFS with area under the ROC curve values of 0.7518 and 0.7355, respectively. Good statistical performance on internal validation was shown by calibration plots and ROC curves. CONCLUSION: This study demonstrated that pre-IBIL was an independent prognostic factor for OS and DFS in LARC patients treated with nCRT followed by TME. Nomograms incorporating pre-IBIL, BMI, smoking history, nCRT with surgery interval, TRG, vascular invasion, and pre-CA19-9 could be helpful to predict OS and DFS.