What is Aspirin's Effect on Colon Cancer?
Taking low doses of aspirin, which inhibits platelet function, after a colon cancer diagnosis appears to be associated with better survival if the tumor cells express HLA class I antigen.
Prior research has suggested aspirin use after a colorectal cancer diagnosis might improve survival. Although the precise mechanism of aspirin's anticancer effect is unknown, previous data suggest that aspirin may prevent distant metastasis in colorectal cancer.
This study examined tissue from tumors from 999 patients with colon cancer who underwent surgery between 2002 and 2008. Tissue samples were examined for HLA class I antigen and prostaglandin endoperoxide synthase 2 (PTGS2). Most patients had colon cancer diagnosed at stage III or lower. Data on aspirin use (defined as patients given a prescription for aspirin for 14 days or more after colon cancer diagnosis) came from a prescription database.
Of the 999 patients, 182 (18.2%) were aspirin users and among them there were 69 deaths (37.9%). There were 396 deaths among 817 nonusers of aspirin (48.5%). Aspirin use after colon cancer diagnosis was associated with improved overall survival compared with nonuse. The potential survival benefit of aspirin was strongest among patients with HLA I antigen expression. The molecular reasons underlying the effects of aspirin are not completely understood, but the authors suggest the results are likely the effect of aspirin on circulating tumor cells and their ability to develop into metastatic deposits.
"We found that the survival benefit associated with low-dose aspirin use after a diagnosis of colon cancer was significantly associated with HLA class I antigen-positive tumors. In contrast, in patients whose tumors had lost their HLA class I antigen expression, aspirin use did not change the outcome."
This study was published in JAMA Internal Medicine (2014; doi:10.1001/jamainternmed.2014.511).