The impact of smoking on survival and extranodal extension in colorectal cancer patients: a retrospective cohort study

Aims: This study aimed to evaluate the impact of smoking on clinical outcomes, including tumor localization, staging, extranodal extension, and overall survival in patients diagnosed with colorectal cancer (CRC).Methods: In this retrospective cohort study, 401 patients with histologically confirmed CRC treated at Erzurum Faculty of Medicine between 2019 and 2023 were analyzed. Based on documented history, patients were classified as smokers or non-smokers. Variables included age, gender, tumor localization, tumor staging (T and N), and presence of extranodal extension (EX). Kaplan-Meier survival analysis and Log-Rank test were used to compare cumulative survival. Chi-square test and Mann-Whitney U test were applied for categorical and continuous variables, respectively.Results: The mean age was 67.4±11.2 years, with smokers being significantly older than non-smokers (69.5±9.6 vs. 66.1±11.8, p=0.005). Tumor localization did not differ significantly between groups. EX was more common among smokers (33.8%) compared to non-smokers (19.4%, p=0.001). Cumulative survival was significantly shorter in smokers (90.2 months; 95% CI: 82.5-97.9) than non-smokers (112.9 months; 95% CI: 107.3-118.5, p=0.001). No significant difference was observed in tumor staging between the groups.Conclusion: Smoking is associated with increased EX and reduced survival in CRC patients. These findings emphasize the importance of smoking cessation in CRC management and suggest that smoking history should be considered in risk stratification and follow-up planning.