Two studies published within the last 12 months are changing medical practice, and doctors have started to encourage patients to take 75 mg of aspirin every day to protect them from colorectal (bowel) cancer.
The most recent study was by researchers at Newcastle University, one of whom described the study's findings as a "huge breakthrough"-and that was before the media could add their hyperbolic spin to the story.
Unfortunately, neither part of the statement is true. In the first place, it's not exactly a break-through-a study published almost a year earlier had come to a similar conclusion. And it isn't quite as huge as the researchers-and the international media-have made out, either.
The study actually made a modest observation. It discovered that aspirin could help to prevent bowel cancer in those with a hereditary disposition, known as 'Lynch syndrome'. The researchers tested the preventative powers of aspirin on 861 patients with the syndrome, and discovered that a regime of 600 mg of aspirin taken daily for nearly six years halved the risk of colorectal cancer (Lancet, 28 October 2011; doi:10.1016/S0140-6736 (11)61049-0).
In the UK, just 5000 people suffer from Lynch syndrome, and not all of these develop bowel cancer. Even if they did, aspirin would be preventing, at best, 2500 cancers a year. This is excellent news, but hardly the stuff of huge breakthroughs that the research-ers, and the world's media, have claimed it to be.
The media also failed to note that two of the sponsors of the study were Bayer Pharma and Bayer Corporation, manufacturers of Aspirin (as opposed to aspirin-containing generics).
The world's media had been whipped into a similar frenzy the year before by a study that concluded that aspirin prevents bowel cancer if a dose of 75 mg is taken every day for at least two years. Again, the headlines-which generally told everyone to start taking aspirin as the ultimate just-in-case therapy-did not paint the true picture.
The study, headed by Professor Peter Rothwell of the Stroke Prevention Research Unit at Oxford University, was a reanalysis of four previously published studies involving 14,033 people who developed bowel cancer over an 18-year period.
Specifically, the study discovered that aspirin could help to prevent proximal colon cancer, a special type of bowel cancer that screening cannot detect. However, it did not prevent two other types of the disease-rectal and distal colon cancers.
The dose was also important. Although low-dose aspirin seemed to have the greatest protective effect, a regular 30-mg dose increased the risk of fatal colo-rectal cancer, according to one of the studies that Rothwell reviewed (Lancer, 2010; 376: 1741-50).
We've been here before. The theory that aspirin has cancer-fighting qualities started to gain traction in the 1990s, when doctors noticed that people who regularly took it appeared to remain free of cancer. Researchers theorized that aspirin and other drugs in the NSAID (non-steroidal anti-inflammatory drug) family could suppress the development of cancer cells by inhibiting the enzyme that changes a healthy cell to a cancerous one.
These early observations were supported by the prestigious Nurses' Health Study, which found an association between regular aspirin use and low cancer rates. Tracking the health of 121,701 nurses, the researchers discovered that those who consistently took four to six aspirins a week halved their risk of developing colorectal cancer. However, it took 10 years before there was any protective effect-and this was doubled to 20 years for those who took aspirin less frequently-and during that time, the women ran a high risk of gastrointestinal bleeding, one of the most common side-effects of aspirin. Also, there was no benefit seen at a four-year follow-up (N Engl J Med, 1995; 333: 609-14).
This was the only major review to find any protective effect. Three years later, a study of more than 22,000 male doctors couldn't find an association. After 12 years, those who took 325 mg of aspirin every other day were just as likely to develop bowel cancer as someone who rarely took aspirin (Ann Intern Med, 1998; 128: 713-20).
Another team of researchers were also unable to find any protective qualities when they gave 40,000 women either 100 mg of aspirin every other day or a placebo. After 10 years-the time when the protective effect was supposed to kick in-researchers couldn't see any difference in cancer incidence between the two groups (JAMA, 2005; 294: 47-55).
No free lunch
Not only doesn't aspirin protect against cancer, but it comes with side-effects that can be fatal. Professor Rothwell alluded to the possibility when he tried to play down the media frenzy over his 2010 study. He said: "I don't think it's necessarily right for the person who did the research to say what guidelines should be [about taking an aspirin every day]. We can't say with absolute certainty that there won't be some unknown harm in taking aspirin for 30 years . . . people have to accept some uncertainty here."
Perhaps he had in mind his own research that he had published in 2007, which suggested that aspirin could be one of the major causes of stroke in the over-75s. This was an extraordinary thing to suggest because the elderly are especially encouraged to take aspirin to prevent cardiovascular problems, such as heart failure and stroke.
Stroke fatalities in the UK have fallen over the past 20 years, and aspirin has been championed as one of the significant factors in the decline. But the figures have excluded deaths among the over-75s-and these have quadrupled over the same period.
Overall, Rothwell discovered that there had been a sevenfold increase in intracerebral haemorrhagic stroke (bleeding in the brain) in that age group, and it coincides with the massive increase in the use of an NSAID, such as aspirin, to help thin the blood. Between 1981 and 1984, just 4 per cent of healthy individ-uals were taking the drug as a just-in-case measure; yet, between 2002 and 2006, this had risen dramatically to 40 per cent of the population.
Rothwell believes that this is more than coincidence. He states, "There are elderly people who take aspirin as a lifestyle choice, and, in that situation, the trials have shown there's no benefit. And what our study suggests is that, particularly in the very elderly, the risks of aspirin outweigh the benefits" (Lancet Neurol, 2007; 6: 487-93).
Everyone knows that aspirin causes gastrointestinal (GI) bleeding-but few realize the seriousness of the effect and that it can sometimes be fatal. In fact, aspirin is seen as such a 'safe' drug that people who take it don't associate it with their GI bleeding.
Researchers from the Eastern Virginia Medical School estimate that the drug is killing 20,000 Americans every year due to GI complications-and yet, none is being recorded as an aspirin-related death.
They base their estimate on a series of interviews they conducted at a hospital that specializes in GI problems. Only one in five patients who were taking aspirin had reported the fact to the hospital because they did not consider it relevant.
"This reflects a common misperception that these medica-tions are insignificant or benign when actually their chronic use, particularly among the elderly and those with conditions such as arthritis, is linked to serious and potentially fatal GI injury and bleeding," said Dr David Johnson, one of the researchers (Proceedings of the 72nd Annual Scientific Meeting of the American College of Gastroenterology, 15 October 2007, Philadelphia, PA).
Extrapolating the figures world-wide, aspirin could be responsible for 100,000 deaths, and 500,000 emergency hospital treatments, each year-and, yet, is not being blamed for any of them.
The Lynch mob
Once the true figures for aspirin-related deaths and injury are factored in, its casual use as a prophylactic (just-in-case remedy) is thrown into question. Indeed, it is difficult to see which group would benefit from its use.
The under-65s run the risk of GI harm for a benefit that seems to be dubious and unproven, while the over-75s-the group that is thought to gain the most from regular use-are likely to suffer a fatal stroke.
In fact, only in those with Lynch syndrome can it be said with any certainty that the benefits of aspirin outweigh the risks. That is hardly cause for screaming headlines and a change in medical practice that may be endangering the lives of many more than it's saving.
WDDTY VOL 22 NO 10 January 2012