Aspirin is an inexpensive drug that can be found in the medicine cabinets of most homes. Could this drug, used for pain and fever reduction, also reduce the risk of cancer?
Several recent studies indicate that taking aspirin daily may reduce cancer risk and prevent cancer from spreading. However, researchers have mixed reviews on the topic, and so far no medical organization has issued guidelines on the use of aspirin as an anti-cancer therapy.
Birmingham oncologist and hematologist Luis F. Pineda, MD says this use for aspirin is not a new concept. “There has been empirical knowledge for some time that aspirin does something to inflammation, and people with cancer do better when they take it,” he says. “Research is showing that the longer they take the aspirin the better the results.”
Pineda points out that recent studies conducted by a research team, led by Peter M. Rothwell at the University of Oxford in England, originally were aimed at aspirin and stroke prevention. “While studying aspirin’s effect on stroke, they realized something was happening with cancer,” he says. “So their data initially wasn’t coming from cancer research, but from neurological research.”
While Rothwell’s studies were based on statistical analysis, they did suggest that with that with prolonged use the risk-reducing benefits of daily aspirin are larger for cancer that for heart disease and stroke. Further studies show that some cancers seem to respond to aspirin use more than others. Rothwell’s findings suggest the largest effect is in adenocarcinomas, which includes stomach cancers and colon cancer, in particular. It also includes breast, esophageal, prostate, and some lung cancers. In terms of preventing the longer-term development of new cancers, the studies showed the largest reductions in the risk of colorectal cancer and esophageal cancer.
Rothwell’s first study pooled data from 51 randomized clinical trials that compared the effect of a daily aspirin against no aspirin on cardiovascular events such as heart attack and stroke. The trials also collected data on cancer. The results from this study showed that aspirin reduced the risk of cancer death by 15 percent and this reduction increased to 37 percent with prolonged use for five years or more. After three years of aspirin use, the incidence of cancer also lessened by 23 percent in men and 25 percent in women.
In a second study, Rothwell’s team looked at aspirin’s effect on metastasis. Results showed that aspirin use decreased the risk of metastasis by 36 percent over the 6.5 year-average duration of the studies and did not vary by age or gender.
Their third study again looked at aspirin’s effect on cancer risk in a review of observational studies instead of clinical trials. Their analysis confirmed their previous findings, and the reductions in risk were similar.
Pineda says these findings correlate to the results of another study using aspirin to treat Lynch Syndrome, a genetic abnormality that causes people to develop malignant polyps in their intestines. “Because of the findings that suggest aspirin prevents these cancers, researchers gave these people adult-sized aspirin. In the first three to five years, nothing happened, but after five years colon cancers decreased 50 percent in the Lynch Syndrome patients,” Pineda says.
These findings have been well accepted by the medical community. “After this study was done to document the effect of aspirin on this group of people, we started seeing recommendations to treat people with the Lynch Syndrome gene with adult aspirin,” Pineda says.
Aspirin can cut the risk of colon cancer, Pineda says, because it blocks the enzyme cyclooxgenase2 which promotes inflammation and cell division and is found in high-level tumors. “Some people believe the reduction in metastatic disease occurs for the same reason that aspirin improves cardiac function. Cancer cells are more adhesive than normal cells and as they travel through the bloodstream they find a place to latch on and create a metastatic niche,” he says. “If aspirin inhibits the tendency for these cells to adhere, the cancer cells won’t survive because they can’t nest anywhere.”
While research findings are making a case for aspirin use and cancer prevention, the American Cancer Society cautions that aspirin is associated with gastrointestinal bleeding and physicians should consult with patients about taking the drug.
Pineda agrees that not everyone can take aspirin, but says that most people can tolerate a baby aspirin each day. He says the findings are interesting and thinks we will hear more about the drug’s use in the cancer field. “As a hematologist, I think aspirin is the best drug ever. It is inexpensive and has a documented epidemiological impact. Now we are adding another benefit to its list,” he says.
A couple of U.S. studies on aspirin and cancer prevention began about five years ago at Harvard University, although so far they haven’t produced any positive results. Pineda doesn’t want his patients to have to wait for definitive results before they can reap the suggested benefits revealed in other studies. “I am a private practice physician, not a scientist, and I am taking these findings seriously,” he says. “I don’t know that we can wait another 20 years for the final verdict on this research, so I am telling my patients to start taking a baby aspirin every day. It won’t cause most of them any problems and the benefits could be significant.”