London: A small dose of aspirin daily could significantly reduce the risk of cancer, cardiovascular disease and blood clots, three new studies have claimed, adding to mounting evidence of the drug's anti-cancer effects.
However, experts said there is still not enough proof to recommend the pill to prevent cancer cases and deaths, and warned that the drug can cause dangerous side effects like stomach bleeds. Many people take aspirin as a heart drug.
The three new studies, published in The Lancet, showed that aspirins not only reduce the chances of contracting cancer, but also prevent it from spreading and cuts the risk of dying from the illness by more than a third.
Oxford University's Prof Peter Rothwell and colleagues, who carried out the latest work, had already linked the drug with a lower risk of some cancers, particularly bowel cancer.
But their previous work suggested people needed to take the drug for about 10 years to get any protection.
Now the same experts believe the protective effect occurs much sooner -- within three to five years -- based on a new analysis of data from 51 trials involving more than 77,000 patients, as reported.
The trials were designed to compare aspirin with no treatment for the prevention of heart disease. But when the team examined how many of the participants developed and died from cancer, they found this was also related to aspirin use.
Taking a low (75-300mg) daily dose of the drug appeared to cut the total number of cancer cases by about a quarter after only three years -- there were nine cancer cases per 1,000 each year in the aspirin-taking group, compared with 12 per 1,000 for those taking dummy pills.
It also reduced the risk of a cancer death by 15 percent within five years. And if patients stayed on the pill for longer, their cancer death risk went down even further – by 37 percent after five years, the researchers claimed.
"This research really shows that the cancer benefit is as large, if not larger, than the benefit in terms of preventing heart attacks and strokes," said Dr Rothwell. "It does change the equation quite drastically."    

According to the researchers, low-dose aspirin also appeared to reduce the likelihood that cancers, particularly bowel, would spread (metastasise) to other parts of the body, and by as much as half in some instances.
In absolute numbers, this could mean for every five patients treated with aspirin one metastatic cancer would be prevented, the researchers estimated.
At the same time, aspirin cut the risk of heart attacks and strokes, but it also increased the risk of a major bleed. However this elevated bleeding risk was only seen in the first few years of aspirin therapy and decreased after that.
Prof Peter Johnson, of Cancer Research UK, said it was still a good idea for people thinking of taking aspirin to discuss it with their doctors because of the possible side effects.
And one should be "aware of the potential for increased complications before surgery or other treatments such as chemotherapy", he said.
However, he added that the findings were exciting and suggested aspirin might be beneficial for treating and preventing cancer, which is something the charity is exploring in its own research.