Although a study recently released showed that patients with colorectal cancer who were regular aspirin users had a 30% better chance of surviving than non-users, and patients who began using aspirin for the first time bus their risk of dying by one half, experts were quick to warn that the drug, a medicine cabinet staple, also had its risks.

Dr. John A. Baron and other medical experts cautioned against starting a daily regimen of aspirin without consulting a physician, because of the risks of gastrointestinal bleeding, and the potential risk for hemorrhagic strokes, or bleeding in the brain. In a large women’s health study, half doses of baby aspirin were associated with a 40 percent increase in serious gastrointestinal bleeds that required transfusions."Using aspirin is a double-edged sword, " attributed Baron.

Aspirin’s anti-cancer property is believed to be linked to its action as a COX-2 inhibitor, a substance which is present in when colorectal tumors are present.

http://www.nytimes.com/2009/08/13/health/13aspirin.html?hp
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A preliminary study suggests that aspirin — used for more than a century and sold for pennies a pill — could find new life as a weapon against colorectal cancer.

The study isn't definitive, but if the results hold up, "it borders on revolutionary," says Alfred Neugut of Columbia University's Mailman School of Public Health, who wasn't involved in the new study.

Aspirin appears to affect the growth of one type of colorectal cancer — that which overproduces the COX-2 enzyme, which promotes both inflammation and tumor growth, says Andrew Chan of Massachusetts General Hospital, co-author of a paper in today's Journal of the American Medical Association. Chan and his colleagues followed nearly 1,300 patients, all of whom received standard therapy for colorectal cancer, for nearly 12 years.

Among patients whose tumors overproduce COX-2, those who began aspirin after diagnosis had a 61% lower risk of dying from their colorectal cancer and a 38% lower risk of dying from any cause, the study says. Aspirin appeared to have no effect on tumors that don't overproduce COX-2. Aspirin also didn't help patients who took it before diagnosis, Chan says. About two-thirds of all colorectal cancer patients have tumors that overproduce COX-2.

Patients who benefited took the equivalent of one regular aspirin a day, Chan says.

Yet experts say it's too early to prescribe aspirin for colorectal cancer. The study had limitations. Although doctors observed patients, they didn't ask anyone to change their lifestyle or medications. So it's possible that people who chose to take aspirin after diagnosis are different in a way that affected their survival. In that case, aspirin couldn't really get credit for beating cancer, Neugut says.

Chan says the only way to truly prove that aspirin fights cancer is to conduct a "gold standard" trial, in which doctors randomly assign one group of people to take a drug, then compare their survival with that of people randomly assigned to a placebo.

Doctors in Singapore are already conducting such a trial, Neugut says.
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