Aspirin may help some people with colon cancer live longer, according to a new study. Researchers looked at nearly 1,000 patients with colon cancer, and tracked them for between four and 10 years. They found 37.9 percent of those who regularly took aspirin died, compared with 48.5 percent of the patients who didn't take aspirin. However, the benefit of taking aspirin was seen only in patients whose tumors made a certain protein, called HLA class I antigen. This protein may be involved in the immune system's response to cancer cells, the researchers said, although more research is needed to understand the mechanism.