Regular use of aspirin after colorectal cancer diagnosis may reduce the risk of cancer death, report Harvard researchers at Massachusetts General Hospital (MGH), Dana-Farber Cancer Institute (DFCI) and Brigham and Women’s Hospital. In today’s edition of the Journal of the American Medical Association, the study’s authors also find that the aspirin-associated survival advantage was seen primarily in patients with tumors expressing the COX-2 enzyme, a characteristic of two-thirds of colorectal cancers.
“While previous studies by our group and others showed that aspirin and other nonsteroidal 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,” says Andrew Chan, Harvard Medical School assistant professor of medicine, of the MGH Gastrointestinal Unit, the study’s lead author. “This is an important first step toward developing targeted approaches to improving patient outcomes.”
Many previous studies have shown that regular use of aspirin and other nonsteroidal anti-inflammatory drugs reduces the risk of developing colorectal cancer. In 2007, the same MGH/DFCI research team found that the benefit only applied to tumors overexpressing COX-2, an enzyme believed to drive tumor growth and known to be inhibited by aspirin and related drugs.
To test their hypotheses that aspirin would also improve the survival of patients diagnosed with colorectal cancer, again through its inhibition of COX-2, the researchers compiled data from two ongoing prospective research studies – the Nurses Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS). Both studies gather comprehensive health information on their participants every two years; data are then analyzed for associations between factors such as medication use and the incidence of several diseases.
The current study focused on 1,279 study participants who were diagnosed with stage 1, 2 or 3 colorectal cancer during their participation in the studies for whom data was available on aspirin use before and after diagnosis. Tumor samples available from 459 participants were analyzed for the expression of COX-2.
Study results indicated that patients who regularly took aspirin – defined as those taking a 325 mg tablet at least twice a week – after their diagnosis had a nearly 30 percent lower risk of dying of colorectal cancer during an average of 11 years after diagnosis than did non-aspirin users. The benefit was especially strong among patients who began using aspirin after diagnosis. In contrast, patients who were aspirin users before diagnosis did not appear to benefit as much from continuing aspirin use after diagnosis. As expected, the survival benefit appeared restricted to patients with COX-2-positive tumors.
“We believe our results could lead to improvements in the therapy of patient with colon cancer,” says Charles Fuchs of Dana-Farber, an HMS associate professor of medicine and the study’s senior author. “We’re now following up this observational study with a randomized trial to evaluate adding the COX-2 inhibitor celecoxib – which is less likely to have the gastrointestinal side effects of aspirin – to standard chemotherapy.”
Study co-author Shuji Ogino is an HMS associate professor of pathology at Brigham and Women’s Hospital. The study was supported by grants from the National Cancer Institute and the Damon Runyon Cancer Research Foundation.