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    Smoking Linked to Some Colon Cancers


    The University of Utah researchers found that colon cancer patients with microsatellite instability were more likely to smoke 20 or more cigarettes a day, were more likely to begin smoking at a young age, and were more likely to have smoked for 35 years or more, compared to colon cancer patients without the genetic error. They found a twofold increased risk associated with cigarette smoking and microsatellite instability in tumors.

    The authors conclude that smoking represents the largest risk factor for microsatellite instability in tumors identified to date. Their findings also could help researchers better understand the pathways involved in the progression to colon cancer. Numerous studies have definitely linked cigarette smoking with the formation of colon polyps known as adenomas, which are precursors to colorectal cancer. But studies evaluating smoking in colon and rectal cancers have been far less conclusive.

    "You would normally expect to see a clear association with cancer when you have such a clear association between a risk factor and a precursor -- in this case, smoking and adenomas," Alfred I. Neugut, MD, PhD, tells WebMD. "This study suggests there might be a subset of colon cancers associated with smoking. If this is the case, that would explain why broader studies have shown no association."

    Neugut was not involved with the study, but wrote an editorial accompanying it in which he urges other researchers to confirm the University of Utah findings.

    "As any good research study does, Slattery's study answers several questions but also raises additional ones," he writes. "She and her colleagues provide one rationale why the smoking and colon cancer relationship has been so inconsistent; the question of why the smoking and adenoma relationship has been so consistent remains."

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