Polyp stopper: controversial drug may prevent colon growths.

An anti-inflammatory drug currently prescribed for arthritis and pain can prevent formation of precancerous growths in the colon and rectum, two analyses suggest. The drug might be especially valuable for people at high risk of developing these kinds of polyps, the data show.

However, regulatory clearance of the drug, called celecoxib, for cancer prevention is far from assured. Two nearly identical trials began in 1999 and 2001 but were stopped in 2004 when more than the expected number of participants developed heart problems while taking the drug, a COX-2 inhibitor.

Pfizer, which markets the drug under the name Celebrex, funded one of the two trials. Since 2005, the company has been required to sell celecoxib with a warning label about its heart risks.

The two research teams identified 3,596 people who had had precancerous colorectal polyps removed during a colonoscopy. The scientists then randomly assigned 2,289 of these participants to take daily celecoxib pills. The others received placebos.

After 3 years, the two teams performed follow-up colonoscopies on roughly three-fourths of the participants. The researchers reported their analyses at a meeting of the American Association for Cancer Research in Washington, D.C., this week.

Celecoxib reduced the number of new polyps. In the two studies, 49 and 61 percent of people taking a placebo developed at least one precancerous polyp during the 3 years between colonoscopies, whereas the proportions of people taking the drug and developing polyps were 34 and 40 percent in the respective studies.

Celecoxib reduced the recurrence of the polyps most dramatically in people whose initial colonoscopies had revealed numerous or large polyps, says gastroenterologist Nadir Arber of the Tel-Aviv Sourasky Medical Center, who presented one of the studies.

"We're very confident" that celecoxib prevents polyps, says oncologist Monica M. Bertagnolli of Harvard Medical School and Brigham and Women's Hospital in Boston, who presented the other of the two new studies. Regarding the drug's safety, she says, "it would be misleading to say we know the answer."

Ernest T. Hawk, an oncologist at the National Cancer Institute in Bethesda, Md., who coauthored the study with Bertagnolli, says that the findings represent "an extremely promising start" to establishing celecoxib as a cancer preventive.

Raymond N. DuBois, a physician and cancer biologist at Vanderbilt University Medical Center in Nashville who didn't participate in the studies, notes that the anticancer effect of celecoxib in the trials was greater than that previously shown for aspirin.

He also says that many of the people who experienced heart problems while taking celecoxib were already at high risk of having such problems. In practice, such patients might be prevented from getting the drug, DuBois says.

Pfizer is currently funding a study to pin down the cardiovascular side effects of the drug. Researchers are monitoring 20,000 people taking celecoxib or other anti-inflammatory drugs, such as ibuprofen or naproxen, for arthritis.