Smoking and survival of colorectal cancer patients: Population-based study from Germany

Current evidence on the association between smoking and colorectal cancer (CRC) prognosis after diagnosis is heterogeneous and few have investigated dose-response effects or outcomes other than overall survival. Therefore, the association of smoking status and intensity with several prognostic outcomes was evaluated in a large population-based cohort of CRC patients; 3,130 patients with incident CRC, diagnosed between 2003 and 2010, were interviewed on sociodemographic factors, smoking behavior, medication and comorbidities. Tumor characteristics were collected from medical records. Vital status, recurrence and cause of death were documented for a median follow-up time of 4.9 years. Using Cox proportional hazards regression, associations between smoking characteristics and overall, CRC-specific, non-CRC related, recurrence-free and disease-free survival were evaluated. Among stage I-III patients, being a smoker at diagnosis and smoking 15 cigarettes/day were associated with lower recurrence-free (adjusted hazard ratios (aHR): 1.29; 95% confidence interval (CI): 0.93-1.79 and aHR: 1.31; 95%-CI: 0.92-1.87) and disease-free survival (aHR: 1.26; 95%-CI: 0.95-1.67 and aHR: 1.29; 95%-CI: 0.94-1.77). Smoking was associated with decreased survival in stage I-III smokers with pack years 20 (Overall survival: aHR: 1.40; 95%-CI: 1.01-1.95), in colon cancer cases (Overall survival: aHR: 1.51; 95%-CI: 1.05-2.17) and men (Recurrence-free survival: aHR: 1.51; 95%-CI: 1.09-2.10; disease-free survival: aHR: 1.49; 95%-CI: 1.12-1.97), whereas no associations were seen among women, stage IV or rectal cancer patients. The observed patterns support the existence of adverse effects of smoking on CRC prognosis among nonmetastatic CRC patients. The potential to enhance prognosis of CRC patients by promotion of smoking cessation, embedded in tertiary prevention programs warrants careful evaluation in future investigations. What's new? Smoking is an established risk factor for a variety of cancers, including colorectal cancer, but evidence regarding its impact on the prognosis of colorectal cancer patients remains sparse. In this population-based study of 3,130 colorectal cancer patients, smoking was associated with reduced survival among patients with nonmetastatic colon cancer. The analyses suggested that the association may be more pronounced in men than women. Future studies should take into account relationships between smoking and other lifestyle factors and should explore the potential role of using the teachable moment of cancer diagnosis in the promotion of smoking cessation.