The latest on this: excerpt from http://www.webmd.com/content/article/120/113880:
The popular arthritis drug Celebrex may help to prevent colon cancer in people at high risk of the disease, but the benefits need to be weighed against the chance of developing heart problems, researchers say. Two large studies released today show that the drug can slash the risk of developing new precancerous growths called polyps by 33% to 45% in people who already have had growths removed.