Caring Currents

An Aspirin a Day Keeps Colon Cancer at Bay

Last updated:

September 04, 2009
aspirin close up

Taking a low dose of a daily aspirin can lower the risk of death from colorectal cancer significantly, according to a new study in the [Journal of the American Medical Association (JAMA).] (http://www.sciencedaily.com/releases/2009/08/090811161308.htm) The study investigated aspirin use among patients with Stage I colorectal cancer, and found they reduced their risk of cancer death by 29 percent. Aspirin use also lowered risk of dying from any condition -- not just cancer -- by 21 percent. The researchers then looked at people with Stage II and Stage III tumors and saw a similar effect.

Here's the thing: Aspirin use is not without its own risks. Aspirin irritates the lining of the stomach, so some people experience indigestion, cramps, or nausea after taking it. It's known to cause stomach bleeding or ulcers, and because it thins the blood can also cause bleeding problems. More rarely, regular use of high doses of aspirin can cause liver or kidney damage.

How Does Aspirin Prevent Colon Cancer?
Experts still aren't sure, but it appears that aspirin blocks or reduces the action of the COX-2 enzyme. This is actually the same mechanism that makes aspirin ease pain and inflammation.

In a previous study by the same research team published in the New England Journal of Medicine, the researchers discovered that taking aspirin did not inhibit all colorectal tumors -- only those that over-express the COX-2 enzyme.

In this study, participants whose tumors tested positive for COX-2 lowered their risk of death by 61 percent and their overall mortality rate by almost 40 percent, so clearly aspirin was of great benefit for them. Those whose tumors were COX-2-negative didn't gain much, if any, benefit from taking aspirin.

This means that aspirin therapy's a gamble; you take it and maybe it will help you, or maybe you'll be one of those who won't benefit. The good news: Between 65 and 80 percent of colorectal tumors are COX-2 positive, so most colon cancer patients fall in this category. And since there aren't a lot of negative side effects from taking aspirin if you're monitored carefully, aspirin therapy is going to be worthwhile for most.

How Much Should Patients Take?
One standard aspirin tablet is 325 milligrams, and many studies have used this dose, either once a day or a little less frequently. The new JAMA study found that all the participants who took one 325-mg dose of aspirin (325mg) at least twice a week (for a total of 650mg or more per week) got the protection. Other studies, still in progress, are looking at the effects of a lower daily dose of 80 milligrams, which requires you to cut tablets into fourths or take baby aspirin. In any case, an aspirin regimen is not something you should embark on without your doctor's approval, so discuss the new research with your doctor and choose your dosage based on her recommendations.

Because the aspirin studies are associational, rather than randomized, cancer experts stopped short of recommending aspirin therapy for colon cancer patients. Their pronouncement was that those already taking aspirin for heart disease would benefit from the additional cancer protection, but that it was too soon to recommend aspirin therapy solely for cancer.

Hmm. Personally, if it was me or someone I loved, I'd have an in-depth discussion with my doctor and question whether this approach is unnecessarily conservative. At this point the aspirin studies have been large, consistent, and impressive, and a 30 to 60 percent reduction of risk is nothing to sneeze at, as my dad would have said.