Celebrex shows promise in lung cancer prevention
By Julie Steenhuysen
CHICAGO (Reuters) - A high dose of the arthritis drug Celebrex showed early signs that it may help prevent lung cancer in heavy smokers, U.S. researchers said on Sunday.
The Pfizer Inc <PFE.N> drug, also known as celecoxib, works by blocking the COX-2 enzyme that causes inflammation, which has been linked with cancer.
A six-month study of 212 current or heavy smokers found a reduction in a specific type of precancerous change in lung cells in people who took a high dose of Celebrex compared with those who took a placebo.
None of the study participants had any heart-related problems such as those with Merck & Co Inc's <MRK.N> now withdrawn arthritis drug Vioxx, another COX-2 inhibitor.
"Celebrex was safe and we did not see any cardiovascular events," said Dr. Edward Kim of M.D. Anderson Cancer Center in Houston, who presented his findings at a meeting of the American Society of Clinical Oncology in Chicago.
He said the study suggests that a high dose of Celebrex might alter some of the cellular changes that lead up to lung cancer. But the finding is very early and would need to be confirmed in longer, larger studies.
"This is not a study where we go tell someone who is a heavy smoker to start taking Celebrex to prevent lung cancer," Kim said in an interview.
Lung cancer is the leading cause of cancer death in the United States, according to the American Cancer Society. In 2008, about 215,000 people will be diagnosed with lung cancer and about 114,000 people will die from it.
The study was started before news emerged in September 2004 that Vioxx doubled the risk of heart attack and stroke in certain patients.
Kim said the trial was put on hold in December 2004 at the request of Pfizer and the National Cancer Institute, which funded the trial, so the researchers could look for signs of heart attacks or strokes.
It was started up again in May 2005 after the researchers added safeguards, including consultations with cardiologists, to reduce heart risks.
Rather than a direct measure of cancer prevention, which could take many years, Kim said the researchers were looking for early changes in the body that might suggest the drug could reduce the chances of developing lung cancer.
Two large, long-running lung cancer prevention studies of beta-carotene and vitamin A supplements found they actually increased the risk of lung cancer.
"We have not had positive results with these studies. Now we would like to search for an intermediate endpoint or biomarker," Kim said at a media briefing.
"Perhaps that will lead us in the direction of who we need to target in the future," he said.
The researchers tested Celebrex in the study because studies in cells, mice and in people have shown the COX-2 enzyme is present at higher than normal levels in lung cancer and in precancerous lesions of the lung, Kim said. COX-2 is thought to play a role in the development of blood vessels that feed tumors.
Kim's study measured levels of the Ki-67 protein, a marker for cell growth. The researchers wanted to see if Celebrex had an impact on levels of this protein in tissue samples taken from the lungs of heavy smokers.
At the beginning of the study, the researchers took lung samples from six predetermined areas of the lung.
People in the study either got a 200 milligram or a 400 milligram dose of Celebrex twice a day, or a placebo.
After three months, they took more lung samples, and they took samples again at six months. Kim said the group that got the higher dose of Celebrex saw a reduction in levels of the Ki-67 protein.
Kim said it will be important to find better ways of identifying people who are at the highest risk for lung cancer for whom the benefits of taking a high-dose COX-2 inhibitor would outweigh any potential heart risks.
(Editing by Tim Dobbyn)