Colon cancer patients who smoked at the time of diagnosis were more likely to die of cancer within five years than patients who never smoked, according to the results of a large population-based cohort study.
The study, “Smoking at diagnosis significantly decreases 5-year cancer-specific survival in a population-based cohort of 18 166 colon cancer patients,” appeared in Alimentary Pharmacology & Therapeutics.
Studies have suggested that smoking increases the risk of cancer-related death and post-operative morbidity in colon cancer patients. But it is still unclear whether smoking is also linked to lower survival rates in non-surgical colon cancer patients.
In an attempt to learn if smoking status at diagnosis is an independent prognostic factor for cancer-specific survival, and if such association depends on the treatment administered to patients, researchers gathered information from the National Cancer Registry Ireland. They collected information from 18,166 colon cancer patients diagnosed between 1994 and 2012, looking particularly at patients’ socioeconomic status, cancer diagnosis and characteristics, and first treatment approach.
At the time of diagnosis, 57 percent of patients had never smoked, 23 percent were ex-smokers (smoked at least once every month in the past, but not in the previous year), and 20 percent were current smokers (smoked at least once every month in the previous year).
Among current smokers, 27 percent had stage 4 colon cancer, compared to 24 percent among ex-smokers and those who had never smoked.
During the five years of follow-up, 488 cancer-specific deaths were registered. The incidence was higher in the current smokers group, with no difference between ex-smokers and never smokers. This trend was consistent even after adjusting for socio-demographic and clinical variables, with smokers having a 14 percent increased risk of cancer-specific death, compared to never smokers.
The incidence of non-cancer-related deaths, on the other hand, was higher in both current and ex-smokers, compared to never smokers. This was suggestive that smoking could be a prognostic factor for cancer-related and all-cause deaths in colon cancer patients.
After stratifying the analysis by treatment, the team revealed that smoking increased the risk of cancer-specific deaths by 21 percent in patients who underwent surgery. But in patients receiving other treatments, no association was found.
These results showed that smoking adversely affects five-year survival of colon cancer patients who have undergone surgery. In addition, smoking’s effects are not only restricted to the time period immediately after surgery, but can extend for longer, as ex-smokers were also at increased risk of death.
“While further research is needed to elucidate mechanisms, continued efforts to encourage smoking prevention and cessation may yield benefits in terms of improved survival from colon cancer,” the researchers wrote.
The authors highlighted that further studies are still required to define whether smoking cessation at the time of diagnosis can improve the outcomes of colon cancer patients.