Surgery Plus Sulindac or Surgery Alone for Advanced Colorectal Cancer

Background: \- Some types of inflammation may increase the risk of cancers in the intestinal track. Because of this possibility, anti-inflammatory drugs may be able to prevent tumor growth and spread. One such drug, sulindac, may be helpful to study. Researchers want to see if people who are having surgery to remove intestinal tumors from advanced colorectal cancer will benefit from sulindac. It will be tested against a placebo. Objectives: \- To see if sulindac can improve treatment outcomes in people who are having surgery for advanced colorectal cancer. Eligibility: \- Individuals at least 18 years of age who are having surgery for advanced colorectal cancer. Design: * Participants will be screened with a physical exam and medical history. Blood samples will be collected. Imaging studies and heart and lung function tests may also be given. * Participants will be separated into two groups. One group will take sulindac. The other will take a placebo. * Participants will take sulindac or placebo twice daily from about 2 to 3 weeks before the scheduled surgery. Seven days before the surgery, they will stop taking the pills. * Participants will have surgery to remove their tumors. The surgery will also remove affected organ tissue. * Participants will start to take the pills again once they have recovered from surgery. They will continue taking the sulindac or placebo twice a day for 3 years, or for as long as the tumors do not return.