Painkillers may not cut smokers' colon cancer risk
NEW YORK, July 7 (Reuters) Aspirin and similar painkillers have been shown to reduce colon cancer risk, but new research suggests the benefits may not extend to longtime smokers.
In a study of nearly 3,300 adults, researchers found that smokers had a higher than average risk of colon cancer, even if they regularly used non-steroid anti-inflammatory drugs (NSAIDs), a class of common over-the-counter pain relievers that includes aspirin, ibuprofen and naproxen.
A number of studies have found a lower risk of colon cancer among people who regularly use NSAIDs, such those who take daily aspirin to help prevent heart attacks. NSAIDs inhibit the body's synthesis of prostaglandins, hormone-like substances that may help stimulate the growth and spread of colon cancer cells.
But the new findings, published in the journal Cancer Research, suggest that the benefits of NSAIDs may not be enough to counteract the damage from years of smoking.
''Given the damage that smokers receive over their lifetime, even strong anti-progression agents, like NSAIDs, may be ineffective,'' write the study authors, led by Victoria Chia of the Fred Hutchinson Cancer Research Center in Seattle.
The study included 1,792 adults with colon cancer and 1,501 without the disease. Overall, Chia's team found that current NSAIDs users had a 30-per cent lower risk of the cancer than nonusers.
Smokers who used NSAIDs, however, still had an elevated risk of colon cancer. Current smokers who were using the painkillers were 70 per cent more likely to be diagnosed with colon cancer than NSAID users who never smoked.
The greatest risk was found among people who'd never regularly used NSAIDs and had smoked for more than 40 years; they were nearly three times more likely to develop colon cancer than non-smokers who used NSAIDs.
In particular, smokers were at risk of a type of colon cancer marked by microsatellite instability, which means the tumor cells show defects in the cells that normally repair the genetic damage that can lead to cancer.
Longtime smokers were at risk of these colon tumors regardless of their NSAID use.
Researchers are currently studying whether aspirin and other NSAIDs can help prevent colon cancer in people with a higher-than-average risk of the disease. Because prolonged NSAID use can cause side effects, such as serious gastrointestinal bleeding, experts advise people against taking the drugs on their own for the sake of colon cancer prevention.
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