Johns Hopkins Health Alert
Smoking and Colorectal Cancer: What the Studies Show
Researchers began investigating the relationship between smoking and colorectal cancer about two decades ago. The initial studies clearly showed that smoking increased a person's risk of developing precancerous colorectal polyps. But the data supporting a link between smoking and colorectal cancer were inconsistent. So, more studies were conducted and now, the results are in.
Researchers at the European Institute of Oncology in Milan recently published findings from two meta-analyses (analyses of findings of a group of smaller studies) that showed smoking clearly increases a person's risk of developing both polyps and colorectal cancer. The first study, published recently in the journal Gastroenterology, analyzed data from 42 previous studies. The researchers found that not only were current smokers twice as likely as people who had never smoked to develop polyps, they were also at greater risk for developing the type of polyp most likely to turn into cancer.
The second study, published recently in JAMA, looked at data from 106 previous studies. This meta-analysis found that smoking increased the risk of developing colorectal cancer by 18%. In addition, the risk of developing rectal cancer was higher than the risk of developing colon cancer: 25% and 12%, respectively. The researchers also found that risk increased in relation to the amount a person smoked. Specifically, regardless of whether a person smoked one pack a day for 50 years and another smoked two packs per day for 25 years, both had a 24% higher risk of developing colorectal cancer than someone who had never smoked.
Findings from a meta-analysis of 36 studies, published last year in the International Journal of Cancer, show that both current and former smokers have a higher risk of developing colorectal cancer than nonsmokers. As with the JAMA study, this report also showed that the risk of rectal cancer was higher than that of colon cancer.
These studies also found that people with colorectal cancer who smoke are more likely than those who don't to die of their disease. In the JAMA study, the odds of dying of colorectal cancer were 25% higher for smokers than nonsmokers. The International Journal of Cancer study found that current smokers were 40% more likely than nonsmokers to die of colorectal cancer.
Posted in Colon Cancer on September 1, 2010
Reviewed January 2011
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