The researchers determined the population prevalence of microsatellite instability-positive (MSI+) colon cancer. They also identified environmental influences in the development of MSI+ tumors.
The results of the study were reported in the October issue of Carcinogenesis.
Microsatellite instability is known to occur in 10-15% of sporadic colon cancers and almost all hereditary nonpolyposis colon cancers.
An epidemiological study of 276 colon cancer cases in Los Angeles County was conducted.
The results supported the association between cigarette smoking and MSI+ recently reported.
Risk of MSI+ colon cancers increased with increasing dose (number of cigarettes per day) and increasing duration (years of smoking) of smoking.
|Increased risk of MSI+ colon cancer:|
- Eating well done red meat
- Fried, barbecued, broiled meats
- Use of meat drippings
Compared with never-smokers, those who smoked 1-20 pack-years and more than 20 pack-years showed odds ratios of 1.39 and 1.64, respectively.
In addition, the results show, for the first time, that patients with MSI+ colon cancers had significantly higher dietary exposure to heterocyclic aromatic amines (HAA). This was determined by two surrogates of high dietary HAA exposure: preference for well-done red meat and high frequencies of certain cooking practices (frying, barbecuing, broiling, and using meat drippings). The association was still significant after adjustment for cigarette smoking habits and red meat intake.
The risk of MSI+ colon cancer was increased 3-fold among patients who preferred to eat red meat that was very well done.
It was increased more than 2-fold among those who frequently fried, barbecued, or broiled their meats, or used meat drippings.
The researchers found that the risk of MSI+ colon cancer associated with cigarette smoking remained statistically significant after adjustment for high dietary HAA exposure.
Anna H. Wu, of the University of Southern California, said on behalf of the group, "There is a significant association between both cigarette smoking and dietary HAA, with a specific subset of colon cancers. This may explain, at least in part, inconsistencies in results linking these two exposures to colon cancers."
"These results provide a potential mechanism of linking HAA exposure and cigarette smoking to a specific subset of colon cancers," she concluded.