Aspirin may reduce risk of bowel cancer by half: Study

By Dr. Ananya Mandal, MDOct 31 2011

According to a new study published in The Lancet, a regular dose of aspirin may not only stave off heart disease but also cut the risk of developing hereditary cancer in half.

The study looked at 1000 patients in 16 countries for more than four years. Researchers at Queens University and Newcastle University in the UK focused principally on people with Lynch syndrome, an inherited genetic disorder that causes cancer by affecting genes responsible for detecting and repairing DNA damage. Around 50% of those with Lynch syndrome develop cancer, and an estimated three of every 100 cases of colon cancer are caused by the syndrome. The study looked at all cancers related to the syndrome–including colon, rectal, stomach, and endometrial. Researchers found that almost 30% of the patients not taking aspirin (they took a starch-based placebo) had developed cancer compared to around 15% of those taking daily aspirin.  For colorectal cancer, the risk reduction was 63%.

More than 600,000 people die of colorectal cancer worldwide every year, and it is the second leading cause of cancer death among men and women in the U.S.

The study revealed that those who had taken aspirin still developed the same number of polyps as those who did not take aspirin. Polyps are abnormal tissue growths of the mucus membrane that are frequently identified as precursors of cancer. The difference for the aspirin takers is that their polyps did not go on to develop cancer, suggesting that aspirin could possibly be causing pre-cancerous cells to self-destruct before they turn cancerous.

The study authors add that unlike the daily 80 mg aspirin regime recommended for those at risk of developing heart disease, patients in this study took 600 mg a day (in two 300 mg pills). That’s a large dose, and taking that much aspirin increases the risk of developing other problems related to degradation of stomach lining, like ulcers, and bleeding complications. Additionally Bayer was one of the study’s sponsors.

Previous observational studies have also suggested that aspirin could be an effective tool against cancer, but this is the first randomized study to test the hypothesis directly. “This is one more piece of evidence that there are some very positive effects of aspirin, and it should be considered very seriously for people who are at risk of colorectal cancer,” says Tim Bishop, one of the authors of the study and a professor of epidemiology at Leeds University in England.

John Burn, lead author of the study and a professor at Newcastle University, said, “We have clear proof that aspirin prevents cancer in people at high genetic risk. We now have new questions to answer: Will low dose be as effective as two aspirins? Should all people at increased risk take aspirin?” Bishop says researchers don't know for sure how aspirin works to prevent cancer, “but one speculation is that the active part of aspirin causes DNA-damaged cells to die.”

“This adds to the growing body of evidence showing the importance of aspirin, and aspirin-like drugs, in the fight against cancer and emphasizes how critical it is to carry out long-term international research,” said Prof Chris Paraskeva, a bowel cancer expert at the University of Bristol.

Eric Jacobs, an epidemiologist with the American Cancer Society, said in statement that “there is good evidence that long-term regular aspirin use can also modestly reduce risk of colorectal cancer in people who do not have Lynch syndrome…However, aspirin use is not currently recommended specifically for cancer prevention because even low-dose aspirin can increase risk of serious stomach bleeding.” Aspirin use should be discussed with a health care provider, he says.

There are many ways to help prevent colorectal cancer, Jacobs adds. “All people 50 or older should get tested for colon cancer, so that precancerous polyps can be found and removed before they ever turn into cancer. In addition, maintaining a healthy weight, being physically active, not smoking and eating less red meat can help lower risk of colorectal cancer.”

The U.S. Preventive Services Task Force already recommends daily low-dose aspirin for healthy men between 45 and 75 and healthy women between 55 and 75 to lower the risk of heart attack and stroke. Scientists who led the study said people with several family members with cancers other than breast, blood and prostate might be advised to start taking aspirin daily from the age of 45.

On Friday the researchers will launch a website to recruit 3,000 people with Lynch syndrome worldwide to take part in a five-year trial to determine the best dose of aspirin to take.