Numerous compounds are examined by the National Cancer Institute (NCI) for their potential to prevent or treat cancer. One class of compounds, cyclooxygenase (COX) inhibitors, is currently being tested in both prevention and treatment clinical trials.
Epidemiologic studies have shown that people who regularly take non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen to treat conditions like arthritis, have lower rates of colorectal polyps, colorectal cancer, and death due to colorectal cancer. NSAIDs block cyclooxygenase enzymes, which are produced by the body when there is inflammation and are also produced by precancerous tissues. Inhibition of COX-2 may help treat and prevent cancer, while inhibition of COX-1 may induce certain medical problems, like stomach bleeding, that occur when NSAIDS are taken regularly for long periods of time.
Pharmaceutical companies have created NSAIDs that block only COX-2; one of them, celecoxib (CelebrexTM), manufactured by Pfizer, Inc., New York, was approved by the U.S. Food and Drug Administration (FDA) for the treatment of both osteoarthritis and adult rheumatoid arthritis (diseases in which the joints are inflamed) in December 1998. Because over a decade of scientific work has suggested the potential of COX-2 inhibitors to prevent and treat cancer, the National Cancer Institute (NCI) has clinical trials under way to look at the efficacy and safety of these drugs.
NCI's Division of Cancer Prevention (DCP) began its studies with celecoxib with a trial in people with Familial Adenomatous Polyposis (FAP). Patients with FAP develop hundreds to thousands of precancerous polyps (adenomas) throughout the colon and rectum. Left untreated, nearly all FAP patients develop colorectal cancer by their 40s and 50s. The primary treatment for FAP is surgical removal of most or all of the colon and rectum with subsequent surveillance of any remaining colorectal segment. In an NCI-sponsored trial, celecoxib helped reduce the number of colon polyps in patients with FAP. The results of this study were published in the New England Journal of Medicine on June 29, 2000, and led to FDA-approval of celecoxib as an adjunctive drug (an accessory or auxiliary agent) that could be added to the standard of care in people with FAP.
As of October 2004, DCP sponsored 23 trials of varying sizes to test the potential of celecoxib to prevent cancer in a number of organ sites. These trials range in size from under 10 participants to more than 2,000 and aim to prevent bladder, breast, cervical, colorectal, esophageal, head and neck, skin, lung, oral, and prostate cancers, as well as multiple myeloma. The majority of these trials are in collaboration with Pfizer, Inc.