Dr. Bill Elliott: Aspirin shows promise in fight against cancer

by Symptom Advice on April 20, 2012

The average person has a 40 percent lifetime risk of developing cancer. your lifestyle has something to do with your risk, but many cancers just happen.

Some of the worst — colon cancer, esophageal cancer, pancreatic cancer and many others — have no symptoms and strike otherwise healthy people who have a generally healthy lifestyle. we can screen for colon, breast, and perhaps prostate cancer, but many other cancers seem to strike as randomly.

Decreased rates of smoking have reduced the rate of lung cancer, but other cancers are increasing in frequency.

Given all that, imagine if a drug company could develop a medication that reduces the risk of getting cancer by as much as 50 percent with almost no side effects. and just for good measure, this new drug also reduces the risk of heart attacks and strokes.

The drug would be a blockbuster. it would make gazillions of dollars for the lucky drug company.

As you have guessed, the medicine already exists, it is virtually free, and available over the counter at any drugstore or supermarket. as has been reported widely, our old friend aspirin is showing real promise against cancer: from prevention to death rate reduction to containment.

Three new studies in England published two weeks ago in the journal Lancet suggest that taking low-dose aspirin daily reduces the rates of cancer — in some cases by as much as 50 percent.

The studies were performed by a group of researchers from Oxford led by Dr. Peter Rothwell. they performed what is known as meta-analyses, a research process in which multiple studies of similar design are pooled to look for results that may have more statistical significance because of larger numbers of patients.

One of the studies combined 51 randomized trials that looked at patients who took low-dose aspirin for up to nine years compared to those who took a placebo. even though cancer incidence was not the outcome the studies were looking for, in retrospect the overall cancer mortality was 40 percent lower in patients that took regular aspirin for more than five years compared to patients in the control group who did not take aspirin. the benefit waned a bit with longer duration of treatment, but there was still a 22 percent lower risk of cancer in patients taking aspirin for more than 20 years.

The biggest benefit in cancer incidence was a decrease in colon cancer and other intestinal cancers where a 38 percent reduction was seen. there was also a reduction in certain types of lung cancers called adenocarcinoma, a type of cancer that is more common among nonsmokers. Aspirin use also was associated with a lower rate of esophageal cancer (the reduction was more than 50 percent), pancreatic cancer, breast cancer and prostate cancer.

In patients who already had cancer, aspirin was associated with a lower rate of spread (metastasis), especially in patients with colon cancer.

The effect was seen with low-dose aspirin, such as the dosages commonly used for heart attack prevention. Aspirin dosages as low as 75 mg were as effective as higher doses (1500 mg or above) in preventing cancer. In other words, more was not better when it came to cancer prevention. Baby aspirin, the most common dose used for heart attack prevention is 81 mg, an effective dose for preventing cancer, according to the studies.

Speaking of heart attack prevention, according to these studies, the benefit from aspirin on cancer prevention was greater than the benefit in preventing heart attacks and strokes.

The biologic mechanism that explains how aspirin prevents cancer has not been worked out, but most experts speculate that it may have to do with aspirin’s effect of reducing inflammation. but there may be other effects that have not yet been discovered.

Aspirin does have its downsides, however. the drug is an effective anticoagulant, and it promotes bleeding. it also is a direct irritant to the stomach lining, and all of the studies showed an increased risk of stomach bleeding associated with the use of aspirin. People with bleeding risks and a history of peptic ulcer disease may not be candidates for aspirin.

Curiously, two large American studies also looked at aspirin usage and did not show a reduction in cancer rates. the Women’s Health Initiative Study and the Physician’s Health Study, which looked at more than 60,000 men and women, were primarily looking at the effect of very low-dose aspirin on heart disease and stroke, but neither study showed a reduced risk of cancer. However both studies used low-dose aspirin every other day rather than daily, perhaps explaining the difference in benefit.

As promising as this research sounds, it is important to talk to your doctor before starting aspirin therapy. even though aspirin is available over the counter and is inexpensive, it obviously has enormous biological effects and is not for everyone.

But if these findings turn out to be confirmed, the implications are stunning. much more research needs to be done before we put aspirin in the water, but it is safe to say that these studies offer a ray of hope in the battle against cancer.

Dr. Bill Elliott is assistant physician in chief for Kaiser Permanente’s Novato office and Petaluma. his column appears every third Monday.

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