As benefits multiply, experts warn of risks

       Cheap, ubiquitous aspirin has long been known for health benefits from basic pain relief to heart attack prevention. But after a new study this week provided tantalising evidence suggesting that aspirin might increase survival chances for colorectal cancer patients, experts were quick to warn that the drug, a medicine cabinet staple,also had its risks.
       "If I were on a desert island, one of the drugs I would choose to have with me, hands down, maybe No.1, is aspirin,"said Dr John A. Baron, a professor of medicine at Dartmouth Medical School."It's a fascinating, wonderful drug, a great drug. But it is a real drug, and it has side effects."
       Dr 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 haemorrhagic strokes, or bleeding in the brain.
       "Aspirin is a drug that been with us a little over 100 years, and we continue to learn impressive and important things about its potential benefits," said Dr Otis Brawley, medical director of the American Cancer Society."But it is a double-edged sword."
       The study found that patients with colorectal cancer who were regular aspirin users had a much better chance of surviving than non-users, and were almost one-third less likely to die of the disease, while those who began using aspirin for the first time after the diagnosis cut their risk of dying by almost half.
       Earlier studies had shown that people who took aspirin regularly were less likely to develop tumours of the colon, but the new study, published in The Journal of the American Medical Association , is the first to have found that patients who had colorectal cancer and took aspirin survived longer.
       One colon cancer expert who commented on the recent study called it "remarkable" and "revolutionary".But then his patients started seeking advice, and he was more circumspect.
       "It's one thing to talk philosophically,"said the expert, Dr Alfred I. Neugut, an oncologist from the College of Physicians and Surgeons at Columbia University who wrote an enthusiastic editorial on the study in this week's Journal of the American Medical Association ."But this is only one study. To know that it's true,it needs to be repeated. Every experiment needs to be repeated once."
       The new study was not a controlled clinical trial, where patients are randomly assigned to receive either a particular treatment or a placebo. That kind of study is considered the gold standard for determining clinical recommendations in medicine, but it is also far more expensive and cumbersome. Observational studies, like this new one, can be weaker or misleading.
       One clinical trial is under way in Asia,where the National Cancer Centre of Singapore is enrolling 2,660 patients with non-metastatic disease in Hong Kong,India, Indonesia and Singapore, who will continue their treatment and be randomly assigned to either get aspirin or a placebo daily for up to three years,according to the National Cancer Institute website.
       Most colorectal cancer tumours are positive for cyclooxygenase-2, or COX-2, an enzyme that is not expressed in a healthy colon but flares up under certain circumstances. The enzyme appears to be involved in fuelling abnormal cell growth and contributing both to the development and spread of the cancer,said Dr Andrew T. Chan, the author of the new study.
       Aspirin's anti-cancer property is believed to be linked to its action as a COX-2 inhibitor.