Patients who participate in this study will be randomly assigned initially to take either celecoxib (the study drug) or placebo (an inactive substance that looks like the study drug). Placebos are used to help determine if the results of a study (good or bad) result from chance or from treatment with the study drug. Patients will have a fifty-fifty chance of initial treatment with the study drug. Neither the patient nor the patient's doctor will know whether he/she is initially receiving the study drug or placebo. Participants who are assigned to initially take placebo may have the opportunity to be treated with celecoxib later in the study.