TORONTO — It’s well-known that popping a low-dose ASA tablet each day helps prevent heart attacks and strokes.
But research now suggests the little pill may also help prevent one of the world’s other great killers — cancer — or at least some kinds of cancer.
British researchers had already found that taking a low-dose ASA tablet daily appears to reduce deaths from colorectal cancer, but further analysis suggests the medicine-cabinet staple may also cut the risk of dying from a number of other malignancies.
Principal investigator Dr. Peter Rothwell, a neurologist at Oxford University, said there were at least 20 per cent fewer deaths from cancer among patients who took between 75 mg and 300 mg of ASA each day, compared to those who didn’t take ASA.
Besides colorectal cancer, the reductions were seen most often for cancers of the esophagus, lung, stomach, prostate and, to a lesser extent, brain.
Still, the Canadian Cancer Society said people should not start throwing back ASA tablets based on the study’s findings, which were not designed to assess the drug’s effects on cancer and should be considered preliminary.
Rothwell and his team, whose work was published online Monday by The Lancet, analyzed data from eight randomized control trials going back to the 1980s that involved more than 25,000 participants in all. For the most part, the studies were devised to see whether taking daily low-dose ASA affected the rate of heart attacks and strokes.
But the research, which compared cardiovascular events among those who took ASA versus those who didn’t, also provided a plethora of data to mine on cancer incidence and deaths among participants both during and after the trials.
“And what we found was that during the trials, there was about a 20 per cent reduction in deaths due to cancer,” Rothwell said Monday from Oxford, England. “But there was nothing at all for the first five years, and that’s what we expected because preventing cancers from developing is going to take a long time to translate through to reducing deaths.”
“What we found was the longer the patients took it, the bigger the benefit, such that if you took it for … 71/2 to 10 years — which was the longest period people took it for (in the trials) — then the risk of cancer death was reduced by over 30 per cent, between 30 and 40 per cent,” he said.
However, the researchers can’t say from their findings whether continuing daily ASA treatment for longer would mean an even greater reduction in cancer death rates.
“What we can’t tell people is what the benefit of taking Aspirin for 20 or 30 years might be,” said Rothwell, noting that many people are prescribed ASA from about age 50 to 70-plus if they have individual risk factors or a family history of cardiovascular disease.
“If you were thinking about when to start taking Aspirin, you’d think, ‘Well, the risk of cancer usually starts to increase steeply at about age 50.’ And if the effect takes five years to be seen, you might want to start thinking about taking Aspirin about age 45, and then continue until about the age of 70, after which the risk of bleeding goes up quite steeply.”
ASA, like any non-steroidal anti-inflammatory drug, or NSAID, can cause gastric bleeding and increase the risk of a hemorrhagic stroke in some people.
Rothwell said the results don’t mean every adult should immediately start taking Aspirin, although they do suggest additional benefits not factored into guidelines for preventing cardiovascular events, he said.
“Previous guidelines have rightly cautioned that in healthy middle-aged people the small risk of bleeding on Aspirin partly offsets the benefit from prevention of strokes and heart attacks. But the reductions in deaths due to several common cancers will now alter this balance for many people.”
While the Canadian Cancer Society welcomes the analysis as a basis for further research, “it’s certainly not anything that would be enough to start making recommendations to the public,” said Heather Chappell, director of cancer control policy.
“One of the limitations is that because the study was looking at cardiovascular events, it wasn’t designed in such a way to take into account the other factors that impact cancer deaths,” she said.
The risk of developing colorectal cancer, for instance, is a complex interplay of genetics, the presence of polyps, body weight, physical activity, diet and tobacco use.
Furthermore, the researchers only looked at cancer deaths — not the risk of developing the disease — and mortality rates from cancers are also affected by a number of factors, including the stage at diagnosis and what effective treatments were available at that point, Chappell said.
“We certainly would want more research done that’s specifically designed to look at the effect of Aspirin on cancer risk, because those types of studies can take into account all the other factors that might be impacting cancer deaths, so that we can make that direct cause-and-effect relationship.”