Smoking status before and after colorectal cancer diagnosis and mortality in Korean men


Session type:

Doeun Jang1,Sunho Choe1,Ji Won Park1,Seung-Yong Jeong1,Aesun Shin1
1Seoul National University College of Medicine



Cigarette smoking is a well-known risk factor for colorectal cancer, however, the effect of smoking after cancer diagnosis on mortality has not been addressed well. Thus, we aimed to evaluate association of pre- and post-diagnosis smoking status with all-cause mortality in colorectal cancer (CRC) patients.


A retrospective cohort consisted with 37,617 male CRC patients who were diagnosed between 2004 and 2014 was constructed from the Korean National Health Insurance Service database. Patients were followed until December 31, 2016. Prediagnostic smoking status was defined information within 2 years of cancer diagnosis, and postdiagnostic smoking status was defined as those after at least 1 year from CRC diagnosis. Pre- and post-diagnostic smoking status was categorized into four groups (non-smoker/non-smoker (reference), non-smoker/smoker, smoker/non-smoker, and smoker/smoker). Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using the Cox proportional hazard model.


During a median of 6.3 years of follow-up, 4,069 patients died. Smokers before CRC diagnosis had higher mortality risk, compared to non-smoker (HR, 1.23; 95% CI, 1.14 to 1.31). Significant elevated mortality in pre-diagnosis smokers were observed regardless of post-diagnosis smoking status (smoker/non-smoker (HR, 1.30; 95% CI, 1.20 to 1.41) and smoker/smoker (HR, 1.13; 95% CI, 1.01 to 1.25)). Among patients with surgical operation only, the quitters after the diagnosis showed a significant reduction in mortality compared to the continual smokers.


Smoking before cancer diagnosis rather than post-diagnosis has stronger impact on prognosis CRC patients, and quitting smoking may improve CRC survival especially among early stage patients.