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.
