Again about Cigarette Smoking and Colon Cancer

A study at University of Rochester Medical Center, has suggested that screening for colorectal cancer, currently recommended to start at age 50 for most people, should start 5 to 10 years earlier for people with a significant lifetime exposure to tobacco smoke.

The study, led by Luke J. Peppone, Ph.D., research assistant professor of Radiation Oncology at the James P. Wilmot Cancer Center at the University of Rochester, examined 3,450 cases and found that current smokers were diagnosed with colon cancer approximately seven years earlier than the ones who never smoked.

This study is also one of the first to associate exposure to second-hand smoke, especially early in life, with a younger age for colon cancer onset.

"The message for physicians and patients is clear: When making decisions about colon cancer screening you should take into account smoking history as well as family history of disease and age," said Peppone.

The researchers also assessed data from patients having colorectal cancer between 1957 and 1997 at Roswell Park Cancer Institute in Buffalo. During this 40 years period, smoking habits changed, with a decrease in the pctage of current or active smokers and an increase in the pctage of previous smokers.

However, the age at colon cancer diagnosis was 6.8 years younger among current smokers and 4.3 years younger for former smokers who quit less than five years ago, the results showed. Also, those who quit more than five years ago had no significant increased risk.

However, people who reported they began smoking as young teens (before age 17) or who smoked heavily (1 pack a day or more) were the most likely to be diagnosed with cancer much younger than their never-smoking counterparts.

Peppone said that past exposure to second-hand-smoke was an additional, significant risk factor, as compared to never smoking. In reality, after combining active smokers and passive smoking into one subgroup, the age at cancer diagnosis was nearly 10 years earlier.

Though, smoking is a well-known risk factor for many cancers, it is only recently that studies have suggested that cigarettes may cause colon cancer. Also, the biological reasons behind the cigarette smoke-colon cancer risk are unclear.

However, it is thought that cigarette smoke reduces the body's resistance to malignancies, just like smoking can depress immune function in general, impairing the ability to fight off infections and viruses.

Carcinogens from smoke reach the bowel through direct circulation or by swallowing smoke and passing it through the intestines. Colorectal cancer is the third most commonly diagnosed cancer among men and women.

The study said that genetics account for about 10 pct of new cases, while more than 75 pct of the cases crop up from sporadic mutations and/or environmental and lifestyle factors such as smoking, a poor diet, alcohol use, lack of exercise and obesity.

Reprinted from: http://www.thecheers.org/news/Science/news_11623_Early-colon-cancer-screening-may-benefit-smokers.html

Smoking Increases Growth of High-Risk Polyps in the Colon

According to recent studies, tobacco smoking seems to promote growth of polyps in the large intestine. Researchers found that current smokers were twice as likely as nonsmokers to develop colon polyps. Former smokers also showed a raised risk, though it was less than that of current smokers.

Moreover, the studies found, smoking was peculiarly connected to "risky" polyps; while most intestibal polyps are not dangerous, high-risk ones are comparatively more likely to become cancerous.

The results give the scientific proof that tobacco smoking contributes to both the formation of polyps and their aggressiveness.

While smoking does seem to be a risk factor for polyps, past studies have been mixed as to whether it raises the risk of colon cancer itself. It can be explained by the fact that many studies may not have followed smokers for a long enough period; any heightened colon cancer risk from smoking could take decades to emerge.

The current results suggest that those who refrain from smoking can lower their risk of polyps and, subsequently, colon cancer.

According to scientists, there's also the possibility that smokers would benefit from earlier colon cancer screening. So, patients are advised to start colon cancer screening at the age of 50, though people at higher-than-average risk, such as those with ulcerative colitis, or a family history of colon cancer, often start earlier.

As a matter of fact, some physicians have already suggested lowering the screening age for longtime smokers.

Intestinal polyps typically emerge after the age of fifty, and the large majority of colon cancers develop after this age as well. But it's still not clear whether smokers tend to develop polyps at an earlier-than-average age, or whether their polyps tend to progress more rapidly to cancer.

What is evident is that both current and former smokers should be especially persistent and careful about following the current recommendations on colon cancer screening.