Aspirin, commonly used to prevent the recurrence of heart attacks or strokes, might also aid in preventing and treating cancer.
"We have now found that after taking aspirin for three or four years there starts to be a reduction in the number of people with the spread of cancers, so it seems as well as preventing the long-term development of cancers, there is good evidence now that it is preventing the spread of cancers," said lead researcher Dr. Peter M. Rothwell, a professor of neurology at the University of Oxford and John Radcliffe Hospital in Oxford.
"Because aspirin prevents the spread of cancers, it could potentially be used as a treatment," he added.
Currently, aspirin is used as a pain reliever, fever reducer, and anti-inflammatory medication, as well as for prevention of strokes and heart attacks. "It may well be that taking aspirin to prevent cancer becomes the main reason for taking it," Rothwell said.
One study showed that taking aspirin five years or more reduced the risk 37 percent, and over three years, the risk reduction was about 25 percent for both men and women, the researchers noted. In another study, researchers looked at the effect of aspirin on slowing the spread of cancer, or metastasis.
Over more than six years of follow-up, low-dose aspirin reduced the risk of distant metastasis by 36 percent, compared with cancer patients receiving a placebo, they found. In addition, aspirin reduced the risk of metastasis in solid tumors, such as colon, lung and prostate cancer, by 46 percent and by 18 percent for cancers of the bladder and kidney.
It also reduced the risk of diagnosing a cancer that had already spread by 31 percent. For those who continued to take aspirin after a cancer diagnosis, the risk of metastasis was cut by 69 percent, the researchers calculated. Aspirin also reduced the risk of dying from cancer by about half. These risk reductions remained after taking into account age and sex, the researchers said.
In a third study, Rothwell's group looked at the effect of aspirin on metastases by analyzing observational studies rather than clinical trials. These studies revealed a 38 percent reduction in colon cancer, which matched well with the risk reduction seen in clinical trials, they said. There were similar findings for esophageal, gastric, biliary and breast cancer, they added.
This research is not conclusive and people should not start taking aspirin in hopes of preventing cancer until further research and examination is done on the subject.