A study published in JAMA August 12th, 2009 concludes:
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.
The researchers explained:
"These results suggest that aspirin may influence the biology of established colorectal tumors in addition to preventing their occurrence. Our data also highlight the potential for using COX-2 or related markers to tailor aspirin use among patients with newly diagnosed colorectal cancer. Nonetheless, because our data are observational, routine use of aspirin or related agents as cancer therapy cannot be recommended, especially in light of concerns over their related toxicities, such as gastrointestinal bleeding."