CAPOX in KRAS Wild-Type Advanced Adenocarcinoma of the Small Bowel or Ampulla of Vater

Panitumumab is designed to "turn off" a protein that is important in cell growth. This may stop the growth of cancer cells. Study Drug Administration: If you are found to be eligible to take part in this study, you will receive the study drug during 14 day study "cycles." On Day 1 of every cycle, you will receive panitumumab by vein over about 60-90 minutes. Study Visits: On or before Day 1 of each cycle: * You will have a physical exam, including measurement of your weight. * Your performance status will be recorded. * You will be asked about any symptoms you may be experiencing and any drugs you may be taking. * Blood (about 2 tablespoons) will be drawn for routine tests. Every 4 cycles: * You will have a chest X-ray or a computed tomography (CT) scan of your chest to check the status of the disease. * You will have a CT or MRI scan to check the status of the disease. If your scan shows that you are responding to the treatment, you will have another CT or MRI scan 6 weeks later. Length of Study: You may continue receiving the study drugs for as long as the doctor thinks it is in your best interest. You will no longer be able to take the study drugs if the disease gets worse or intolerable side effects occur. End-of-Treatment: After you stop taking the study drugs for any reason, you will have an end-of-treatment visit. The following tests and procedures will be performed: * You will have a physical exam, including measurement of your weight. * Your performance status will be recorded. * You will be asked about any symptoms you may be experiencing and any drugs you may be taking. * Blood (about 2 tablespoons) will be drawn for routine tests. * If the doctor thinks it is needed, you will have a CT or MRI scan of the abdomen and pelvis to check the status of the disease. Follow-Up: Thirty (30) days after your last dose of study drug(s), you will be asked about any symptoms you may be experiencing and any drugs you may be taking. If you are unable to come to MD Anderson for this, the study staff will call you and ask you these questions. This call will last about 30 minutes. You will then be called every 3 months and asked the same questions. Each call will last about 15-30 minutes. If you are taken off study treatment for reasons other than the disease getting worse, you will have a CT or MRI scan of the abdomen and pelvis to check the status of the disease every 12 weeks (+/- 2 weeks) after the End-of-Treatment visit. This will be done until the disease gets worse and if you do not start any other anti-cancer treatment. This is an investigational study. Panitumumab is commercially available and FDA approved to treat a certain type of colorectal cancer. Its use in this type of cancer is investigational. Up to 27 patients will take part in this study. All will be enrolled at MD Anderson.