Cancer is the first condition where experts have personalized treatment, matching genetics of the tumor to the appropriate chemotherapy; and now it may be the first in which prevention, too, can be personalized, the Fox News reported.

Two decades after scientists discovered that aspirin might reduce the risk of colorectal cancer, a new study finds that it has that benefit almost exclusively in people with genes that produce high levels of a particular enzyme. 

Both the enzyme, called 15-PGDH, and aspirin target prostaglandins. These molecules promote the growth of colon cells and also inflammation; both increase the risk of cancer.

Dr Andrew Chan of Massachusetts General Hospital in Boston and his team mined the long-running Nurses' Health Study and the Health Professionals Follow-Up Study, both based at Harvard School of Public Health and sister institutions. Among the 127,865 participants were 270 cases of colorectal cancer for which the Boston team had records of aspirin use.

In people whose DNA produces high levels of the enzyme, regular aspirin use reduced the risk of colorectal cancer by half, and possibly by as much as two-thirds. In people with lower levels, aspirin use reduced risk by only 10 percent, and may have increased it.