The purpose of this study was to explore the association of smoking status and clinically relevant duration of smoking cessation with long-term survival after lung cancer (LC) or colorectal cancer (CRC) diagnosis. We compared survival of patients with LC and CRC who were never-smokers, long-term, medium-term, and short-term quitters, and current smokers around diagnosis.
We studied 5,575 patients in Cancer Care Outcomes Research and Surveillance (CanCORS), a national, prospective observational cohort study, who provided smoking status information approximately 5 months after LC or CRC diagnosis. Smoking status was categorized as: never-smoker, quit > 5 years prior to diagnosis, quit between 1-5 years prior to diagnosis, quit less than 1 year before diagnosis, and current smoker. We examined the relationship between smoking status around diagnosis with mortality using Cox regression models.
Among participants with LC, never-smokers had lower mortality risk compared with current smokers (HR 0.71 95% CI 0.57 to 0.89). Among participants with CRC, never smokers had a lower mortality risk as compared to current smokers (HR 0.79, 95% CI 0.64 to 0.99).
Among both LC and CRC patients, current smokers at diagnosis have higher mortality than never-smokers. This effect should be further studied in the context of tumor biology. However, smoking cessation around the time of diagnosis did not affect survival in this sample.
The results from our analysis of patients in the Cancer Care Outcomes Research and Surveillance (CanCORS) consortium, a large, geographically diverse cohort, show that both lung and colorectal cancer patients who were actively smoking at diagnosis have worse survival as compared to never smokers. While current smoking is detrimental to survival, cessation upon diagnosis may not mitigate this risk.