Scientific evidence has established that smoking contributes to the development of colon cancer. The chemicals present in tobacco smoke can increase an individual’s risk of developing this disease. Understanding these biological connections highlights the importance of avoiding tobacco use for cancer prevention.
The Biological Link Between Smoking and Colon Cancer
Tobacco smoke contains carcinogenic chemicals. When inhaled, these carcinogens are absorbed into the bloodstream and circulate throughout the body, damaging the DNA within the cells lining the colon and rectum.
DNA damage can lead to mutations, which are changes in the genetic code. These mutations can disrupt the normal control mechanisms of cell growth, leading to uncontrolled cell division and tumor formation. Some studies indicate that tobacco toxins might specifically hinder DNA repair proteins, making colon cells more vulnerable to accumulating genetic damage. For instance, certain mutational signatures, such as SBS4, have been directly linked to tobacco consumption in colorectal cancer tumors.
Smoking’s Impact on Colorectal Polyps
Most colorectal cancers originate from polyps, particularly adenomatous polyps, which are considered precursors. Research shows that smoking increases the likelihood of developing these polyps.
Smoking contributes to polyp formation and influences their characteristics, making them more prone to becoming cancerous. Studies indicate that current smokers face a higher risk of developing both conventional adenomas and serrated polyps compared to non-smokers. The duration and intensity of smoking are also associated with an increased prevalence of larger or multiple adenomas, indicating a dose-response relationship.
Quantifying the Cancer Risk
Smoking increases the risk of developing colorectal cancer. Smokers have an elevated risk, with some studies indicating up to a 60% higher risk compared to non-smokers. A large prospective study found that current and former smokers had a 27% higher risk of developing colorectal cancer, even after accounting for other factors like screening.
The risk also increases with smoking duration and daily cigarette consumption. For instance, male ever smokers have been observed to have a 39% higher risk of cancer in the left colon, while female ever smokers show a 20% higher risk in the right colon. Smoking is also associated with increased mortality; current smokers diagnosed with colorectal cancer face a 14% higher likelihood of death.
Reducing Risk After Quitting
Quitting smoking offers health benefits, including a reduction in the risk of colorectal cancer. The elevated risk begins to decline after cessation. The sooner and longer an individual remains smoke-free, the greater the risk reduction.
While some risks, like those for mouth or throat cancers, can be cut in half within 5 to 10 years, the decline for colorectal cancer risk can vary by subsite. For proximal colon and rectal cancers, the excess risk may decrease relatively soon after quitting, but for distal colon cancer, the elevated risk can persist for up to approximately 20 to 25 years post-cessation. Quitting at any age provides benefits, adding years to one’s life.