Smoking Increases Colon Cancer Risk in Women

Women who smoke have an increased risk of developing colon cancer as compared with men who smoke, according to a Norwegian study published in the journal Cancer Epidemiology, Biomarkers & Prevention. A number of studies have shown that smoking ups colon cancer risk. For example, a study published recently in the Journal of Clinical Oncology reported that smoking was significantly associated with shorter DFS (disease free survival) rates and TTR (time to recurrence) rates in patients with colon cancer. These adverse relationships were most evident in patients with BRAF wild-type or KRAS mutated colon cancer.

Another study published in the journal Clinical Gastroenterology and Hepatology revealed that smoking for at least 20 years was associated with a 26 percent increase in risk of colorectal cancer, compared with never smokers, and smoking 20g tobacco or more each day was associated with a 30 percent increase in risk.

An earlier study from the Cancer Research Center of Hawaii, University of Hawaii, even suggested that there could be a difference in risk with the type of tobacco product. Non-filtered cigarettes increased risk of both colon and rectal cancer, whereas filtered cigarettes seemed to increase risk of rectal but not colon cancer. ‘The effect of smoking was not limited to the distant past, and accumulated pack-years of smoking seemed to be more important than the time in which smoking occurred’, said the researchers of the study.

The present study however represents the largest of its kind to demonstrate the link between smoking and colon cancer. It is also the first to show that 'while the risk is increased in both men and women, it is most pronounced in women smokers'.

'Our study is the first that shows women who smoke less than men still get more colon cancer,' said Inger Torhild Gram from the Department of Community Medicine, University of Tromsø, Norway.

Gram and her colleagues followed 602,242 participants aged 19 to 67 years at enrollment in 1972–2003, by linkage to national registries through December 2007. Sixty three percent of the participants were ever-smokers (59 percent women and 67 percent men).

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During the follow up of 14 years, the results were interesting -

• A total of 3,998 participants comprising 46 percent women developed colon cancer.

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• Women ever-smokers had a 19 percent and male ever-smokers an 8 percent increased risk of colon cancer compared with never smokers.

• Women who started smoking when they were 16 or younger and women who had smoked for 40 years or more had an increased risk of about 50 percent, compared with never-smokers and almost about 48 percent compared to men who smoked.

• Compared to men who smoked, women ever-smokers those who smoked 20 or more cigarettes daily were 28 percent more likely to get cancer; and those who smoked 20 or more pack years were 33 percent more likely to develop colon cancer as against men.

• Women ever-smokers had a significantly increased risk of 31 percent for proximal colon cancer when determined on the basis of location of the cancer.

Smoking is associated with flat colorectal adenomas located mainly in the proximal colon and 'which is exactly where we found them more often in women,' said Gram.

'The study, which is just getting underway, is using data from the University's multiethnic cohort, so will also reveal whether the findings apply only to Caucasians or to other ethnicities as well,' she added.

The findings thus send a clear message - Quit smoking!

Reference:

http://cebp.aacrjournals.org/content/early/2013/04/29/1055-9965.EPI-12-1351.full.pdf+html
http://www.ncbi.nlm.nih.gov/pubmed/23547084
http://www.ncbi.nlm.nih.gov/pubmed/23142208

Source-Medindia