Does continuing to smoke after diagnosis of colorectal cancer affect survival?

This study investigated the effect of smoking on survival in patients with colorectal cancer.

Colorectal cancer is the third most common cancer in the world. There is no one cause of colorectal cancer but several environmental and genetic factors are known to contribute to its development. The International Association for Research on Cancer added colorectal cancer to the list of cancers linked with smoking in 2009. However, very little is known about the impact of smoking on survival in colorectal cancer survivors.

This study included 2548 patients with non-metastatic colorectal cancer (colorectal cancer that has not spread to other areas). All patients were part of a large scale nutrition study, which followed roughly 184,000 Americans from 1992 to 2009. Patient smoking status was determined based on questionnaires, filled in every 2 years after 1997. Overall survival time (time until death from any cause) and colorectal cancer-specific survival time (time until death from colorectal cancer) was also investigated for all patients.

Patients who smoked after their diagnosis had worse survival rates than patients who had never smoked. Patients who smoked after their diagnosis had 2.2 fold higher risk of death from any cause than patients who had never smoked. They also had a 92% increased risk of colorectal cancer specific death. There was no difference in the risk of death between patients who smoked less than 15 cigarettes per day and those that smoked more than 15 per day.

Patients who were former smokers did not have an increased risk of death from their colorectal cancer. However, they had a slightly higher risk of death from any cause (18% higher risk).

The authors concluded that smoking after diagnosis of colorectal cancer is associated with a nearly two-fold higher risk of death compared to colorectal cancer survivors who have never smoked.