Colorectal cancer patients with early stage disease were 30 percent less likely to die from cancer and 20 percent less likely to die at all if they took aspirin regularly after their diagnosis.
Benefit was even greater for those who began taking the medicine for the first time after their diagnosis.
However, only the group whose tumors tested positive for COX-2 (cyclooxygenase2) benefited from aspirin.
COX-2 is an enzyme that produces inflammation and pain, and aspirin blocks its activity. About two-thirds of colon cancers express COX-2.
Data about aspirin use was collected every two years from participants in the Nurses Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS). Regular aspirin use was defined as taking a 325 milligram tablet at least twice a week.
Almost 1,300 people in the two studies were diagnosed with stage I, II, or III colorectal cancer and were followed after surgery.
For all patients, regardless of COX-2 status, after a median follow-up of almost 12 years:
- 15 percent of patients who took aspirin regularly had died from colorectal cancer compared to 19 percent of non-aspirin users.
- 35 percent of aspirin-users had died from any cause compared to 39 percent of non-users.
- All patients who took aspirin were 29 percent less likely to die of colorectal cancer and 21 percent less likely to die from any cause than non-users.
- Those patients who began taking aspirin after their colorectal cancer diagnosis were 47 percent less likely to die from colorectal cancer.
- Patients with COX-2 expression in tumor tissue had a 41 percent reduction in risk of dying from colorectal cancer if they were aspirin users.
- In those without COX-2 over-expression, aspirin made no difference in risk of death from colorectal cancer.
The study team concluded,
Regular aspirin use after the diagnosis of colorectal cancer is associated with lower risk of colorectal cancer–specific and overall mortality, especially among individuals with tumors that overexpress COX-2.
Andrew Chan, MD, MPH, gastroenterologist from Massachusetts General Hospital and Harvard Medical School, who led the study said,
While previous studies by our group and others showed that aspirin and other non-steroidal anti-inflammatory drugs reduce the risk of developing colorectal cancer, this study is the among the first to show that aspirin can also improve survival in patients who have already been diagnosed with colorectal cancers. Moreover, the benefit appeared to be especially strong among patients with cancers that express COX-2. This is an important first step toward developing targeted approaches to improving patient outcomes.
Previous research has shown that aspirin reduces the risk of new colon polyps in patients recovering from early stage colon cancer.
In an editorial accompanying the JAMA article, Alfred Neugut, MD, PhD, professor of medicine and epidemiology at Columbia University, wrote,
A major recent priority in clinical oncology has been to develop biomarkers for prognosis and to predict response specific to interventions.The specificity of the response of colorectal cancers to aspirin for patients in whom tumors over-expressed Cox-2 suggests that this potential future treatment comes with its own ready-made predictive biomarker.
There is currently no commercial test on the market that tests for COX-2 in tumor tissue. However, testing is available at academic cancer centers and research facilities.
SOURCE: Chan et al., Aspirin Use and Survival After Diagnosis of Colorectal Cancer, Journal of the American Medical Association, Volume 302, Number 6, August 12, 2009.
What This Means for Patients
While this is good news for people with stage I, II, or III colon or rectal cancer, it is too early to make a widespread change in how colorectal cancer is treated after surgery.
Discuss using aspirin with your doctor before using it — either on a short or long term basis.
Researchers didn’t randomly assign some patients to take aspirin and others to use a placebo or sugar pill. Instead, they asked people in the study to tell them about how much aspirin they remembered taking every two years. There was no uniform reason for taking aspirin or uniform daily or weekly dose.
Stronger, randomized studies are important before recommendations for aspirin use for all early stage patients can be made.
Aspirin can cause bleeding in the stomach and gastrointestinal tract, sometimes serious enough to be life-threatening.
Because it may interfere with blood clotting, aspirin should be avoided before surgery, during chemo, and before a colonoscopy. Tell your doctors if you are taking aspirin.