Evaluation of oxidative balance scores using different methods and their relationships with colorectal cancer...

The Oxidative Balance Score (OBS), a composite measure of systemic oxidative stress, has demonstrated potential relevance in cancer outcomes. However, epidemiological evidence linking OBS to colorectal cancer (CRC) survival remains limited and methodologically heterogeneous. This study aims to explore the associations between OBS and survival outcomes among CRC patients. We included 2799 patients from the Guangdong Colorectal Cancer Cohort study. Four OBSs were calculated based on distinct methodologies, and comparative analyses were conducted. Cox proportional hazards regression models were used to examine the associations between each OBS and overall survival (OS) and CRC-specific survival (CSS). Restricted cubic spline models assessed nonlinear associations. Stratified analyses examined effect modification by sex and tumor site. Additionally, weighted quantile sum (WQS) regression was applied to identify dominant antioxidants and pro-oxidants within each OBS. During a median follow-up of 60.33 months, 639 deaths were recorded, including 574 CRC-specific deaths. OBS-2 showed the best model fit and discriminatory ability. Patients with higher OBS-2 and OBS-3 scores had a significant prolonged CSS. Specifically, compared to the lowest quartile (Q1), the hazard ratios (HRs) and 95 % confidence intervals (CIs) for the highest quartile (Q4) were: OBS-2: HR_{Q4 vs. Q1}, 0.76; 95 % CI: 0.59, 0.98; and OBS-3: HR_{Q4 vs. Q1}, 0.76; 95 % CI: 0.59, 0.96. OBS-1 and OBS-4 showed borderline inverse associations with CSS. For OS, only OBS-1 demonstrated a borderline inverse association. All associations appeared linear (all P-Nonlinear >0.05). The inverse associations were more pronounced in rectal cancer patients. WQS regression identified selenium, n-3 polyunsaturated fatty acids, and vitamin B₁₂ as primary antioxidant contributors, whereas iron emerged as the predominant pro-oxidant. In conclusion, higher OBS-2 and OBS-3 scores were associated with improved CSS in CRC patients. These findings may help inform future recommendations for lifestyle-based interventions aimed at improving prognosis in this population.