Taking Aspirin After Colorectal Cancer Diagnosis May Improve Survival
Reported August 11, 2009
NEW YORK (Reuters Health) – New “compelling evidence” suggests that aspirin may have a benefit, not only for the prevention of colorectal cancer, but for its progression and spread as well.
Based on the findings, “Regular use of aspirin after diagnosis of colorectal cancer is associated with improved colorectal cancer-specific and overall survival,” Dr. Andrew T. Chan, of Massachusetts General Hospital and Harvard Medical School, Boston, and an investigator involved in the study, wrote in an email to Reuters Health.
The benefits of aspirin appear to be confined to those patients whose primary tumors are cyclooxygenase 2 (COX-2)-positive, the researcher noted. “This is consistent with our understanding of aspirin’s ability to block COX-2, which is known to be an important mechanism in colorectal cancer growth and development,” Dr. Chan explained.
Although it is well-established that aspirin can reduce the risk of developing colorectal cancer, less is known about the effect of aspirin among patients with established colorectal cancer.
Dr. Chan and colleagues therefore studied the association bserum TSH concentration above the reference rangeetween aspirin use and survival among 1,279 men and women with nonmetastatic (stages I, II and III) colorectal cancer participating in two large prospective cohort studies initiated in 1980 and 1986, with follow-up lasting through June 1, 2008.
After a median follow-up of 11.8 years, among 549 patients who regularly took aspirin after diagnosis, there were 193 total deaths (35%) and 81 colorectal cancer-specific deaths (15%).
That compared with 287 total deaths (39%) and 141 colorectal cancer-specific deaths (19%) among 730 patients who did not take aspirin.
In the August 12 issure of the Journal of the American Medical Association, Dr. Chan and colleagues report that patients who used aspirin after diagnosis had a 29% lower cancer-specific mortality and a 21% lower overall mortality than non-aspirin users.
Among the group of patients that did not use aspirin prior to diagnosis, starting aspirin after diagnosis was associated with a 47% lower risk of colorectal cancer-specific death and a 32% lower risk of overall death. In contrast, in patients who were using aspirin prior to diagnosis, continuation of aspirin after diagnosis was not associated with a significant reduction in mortality.
As expected, COX-2 tumor status influenced the effect of aspirin on mortality. Among patients with COX-2-positive tumors, regular aspirin was associated with a 61% lower risk of colorectal cancer-specific mortality and 38% lower risk of overall mortality. Post-diagnosis aspirin use was not associated with lower mortality risk in patients with COX-2-negative tumors.
“This supports the hypothesis that COX-2-positive tumors may be relatively sensitive to the anticancer effect of aspirin, whereas COX-2-negative tumors may be relatively aspirin-resistant,” Dr. Chan and colleagues note in their report.
“Moreover, it potentially explains the observation that the benefit of postdiagnosis aspirin use on patient survival was not apparent among patients who used aspirin prior to cancer diagnosis.”
In a related commentary, Dr. Alfred I. Neugut of Columbia University, New York, notes that the survival benefits of aspirin were “similar in patients who received standard adjuvant chemotherapy and those who did not, and in patients with stage I and stage II disease as well as in those who had stage III disease at diagnosis.”
“Thus, aspirin may have the potential to be useful as adjuvant therapy not just for locally advanced disease but for early stage patients as well.”
Source:JAMA 2009;302:649-659;688-689.
