Despite the relevance of other genes controlling oxylipin synthesis for the chemopreventative property of aspirin, the relationship between SNP genotypes in a wide range of genes controlling oxylipin synthesis and levels (including PTGS1 and PTGS2, as well as ALOX5, ALOX12, and HPGD) and the effect of aspirin on colorectal polyp risk has not been addressed previously in a randomized trial setting. This evidence concerns the gene PTGS1 and polyp of large intestine.