The recent observation [40] that the improvements in cancer and overall mortality seen in two large prospective cohorts associated with aspirin use after a diagnosis of colorectal cancer correlate with the presence of mutated PIK3CA within the tumour provides further insights into the possible anti-cancer mechanisms of aspirin, as well as raising the possibility that molecular profiling may be able to select patients most likely to respond to aspirin. This evidence concerns the gene PIK3CA and colorectal cancer.