Can Aspirin Help Prevent Cancer? - the pros and cons
Two physicians at Harvard Medical School, Drs. Michelle Holmes and Wendy Chen, recently wrote in the New York Times about the apparent ability of regular aspirin use to prevent death in women with breast cancer. They called for a randomized trial of aspirin, enrolling 3000 women with stage 2 and 3 breast cancer for five years, which they estimate would cost $10 million. They have repeatedly tried to raise these funds through federal grants, and have been rejected. It is possible that the publicity from their article will result in funding from the government, private foundations or private individuals. The first randomized clinical trial of aspirin is now going on in Britain, funded by a nonprofit group. They are looking at 4 cancers - colorectal, breast, gastro-esophageal, & prostate - with results expected by 2025.
Evidence so far: Many studies in the past 20 years have shown that taking aspirin is associated with the prevention of colon cancer. A recent study helped to refine the findings - people with high amounts of an enzyme known as 15-PDGH in their gut lining had a 50% lower risk of colon cancer than those with a low level, if they took the equivalent of 2 regular strength aspirins a week. A regular strength aspirin is 325 mg, and a ‘baby’ aspirin is usually 81 mg. (2 x 325=650, and 7 X 81=567 - close enough). The test for 15-PDGH is not yet available. People at high risk for colon cancer - a diet low in vegetables and whole grains, high in red meat and processed meat, inactivity, obesity, smoking, family history of colon cancer - should talk to their doctor about the pros and cons of low dose aspirin. (People with these habits might also want to make some life-style changes.)
Breast cancer: a Columbia University study published in 2004 showed that women who took aspirin regularly (the 325 mg or 81 mg dose was not distinguished) were 20–30% less likely to develop hormone positive breast cancer. Aspirin did not decrease the risk of hormone negative breast cancer. The proposed mechanism is that by a series of physiologic steps, aspirin decreases hormone biosynthesis in the body. The researchers also discussed the anti-inflammatory properties of aspirin, which may reduce cancer risk overall. NSAIDS such as ibuprofen were also associated with slightly decreased cancer risk, but not as great as aspirin. Acetaminophen (Tylenol) did not show a protective effect. Another study, published in 2010 by the authors of the recent NYTimes article, looked at data from The Nurses Health Study in the US. It found that in women living at least 1 year after a breast cancer diagnosis, aspirin use was associated with a decreased risk of distant recurrence and breast cancer death.
A recent study from the National Cancer Institute showed that daily aspirin use may reduce the risk of ovarian cancer by 20%. About 20,000 women in the US will be diagnosed with ovarian cancer in 2014, and more than 14,000 will die of this disease, which is hard to diagnose early enough for a cure. Early symptoms are non-specific, such as abdominal bloating, pelvic or abdominal pain, feeling full quickly, and urinary frequency.
Many people take aspirin to prevent heart disease, especially if they have already had a heart attack - to prevent another. Paramedics regularly give aspirin to a heart attack patient on the way to the hospital. Heart attacks and strokes occur when the blood supply to a part of the heart muscle or brain is blocked by ‘plaque’, a buildup of cholesterol, fatty substances, cellular waste products and calcium. Aspirin helps to prevent blood clotting in the presence of plaque. The dose to take should always be discussed with your health care provider.
There are side effects of aspirin use, which is why it cannot be recommended to everyone to reduce the risk of cancer or heart disease. Aspirin can be irritating to the stomach and can cause serious bleeding in the gastrointestinal tract. It can also cause bleeding in the brain, known as a hemorrhagic stroke.
Here’s the real message of this column: it looks as though a simple medicine - aspirin - could be very important in the prevention of many common cancers. However, because of the possible side effects and dangers of aspirin, randomized studies are greatly needed to show its efficacy and safety. Funding is needed for this, and it will not come from pharmaceutical companies, as aspirin is such a common and inexpensive drug. The recent publicity about this subject has stirred great interest. Hopefully there will soon be such studies -with answers coming more quickly than the British study due to be finished in 2025!
Sadja Greenwood, MD,MPH back issues on this blog