Crossover Trial of Systemic Chemotherapy in Patients With Metastatic Well-Differentiated Mucinous Appendiceal Adenocarcinomas With Pseudomyxoma Peritonei

Study Groups: If you are found to be eligible to take part in this study, you will be randomly assigned (as in the flip of a coin) to 1 of 2 study groups (cohorts): * If you are in Cohort A, you will first be observed for 6 months, then you will receive chemotherapy for 6 months. * If you are in Cohort B, you will first receive chemotherapy for 6 months, then you will be observed for 6 months. You will have an equal chance of being assigned to either cohort. No matter which cohort you are in, the type of chemotherapy you receive will depend on the standard of care for the disease and what your doctor thinks is in your best interest. You will sign a separate consent form for chemotherapy that explains how the drug is given, as well as its risks and benefits. Study Visits: Every 3 months (+/- 2 weeks) for 12 months: * You will have a physical exam, including measurement of your weight and blood pressure. * Your performance status will be recorded. * Blood (about 2 tablespoons) will be drawn for routine tests. * You will complete the 3 questionnaires about your quality of life. * You will have an MRI or a CT scan to check the status of the disease. Length of Stud: You will be on study for up to 12 months. You will no longer be able to take part in this study if the disease gets worse, if intolerable side effects occur, or if you are unable to follow study directions. Your active participation on the study will be over after the end-of-treatment visit. End-of-Treatment Visit: The end-of-treatment visit will be the same as your 4th study visit. Twelve (12) months (+/- 4 weeks) after you began the study, the following tests and procedures will be performed: * You will have a physical exam, including measurement of your weight and blood pressure. * Your performance status will be recorded. * Blood (about 2 tablespoons) will be drawn for routine tests. * You will complete the questionnaires you completed at screening. * If one was not performed within 4 weeks before this visit, you will have an MRI or a CT scan to check the status of the disease. Long-Term Follow-Up: After the end-of-treatment visit, you will be followed 1 time each year by checking your medical record and seeing how you are doing. If nothing is in your medical record, you will be called and asked about how you are doing. This call should last about 5-10 minutes. This is an investigational study. Up to 30 patients take part in this study. All will be enrolled at MD Anderson.