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

Inclusion Criteria: 1. Patients must have histologically confirmed adenocarcinoma of the small bowel or ampulla of Vater that is either unresectable or metastatic. 2. Adequate tumor tissue available for KRAS mutational analysis or known KRAS wild-type status. 3. Prior progression on or intolerance to treatment with a fluoropyrimidine and oxaliplatin. Recurrence of disease within 6 months from the completion of adjuvant therapy with both a fluoropyrimidine and oxaliplatin is considered progression. 4. Patients must have measurable disease as per the revised Response Evaluation Criteria In Solid Tumors (RECIST) criteria (Version 1.1). 5. If radiation was previously received, the measurable disease must be outside the previous radiation field, unless this area has demonstrated evidence of radiographic growth. 6. A minimum of 2 weeks must have elapsed from completion of any prior chemotherapy or radiotherapy or surgery and the start date of study therapy. 7. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 - 2. 8. Adequate organ function including: a) Absolute neutrophil count (ANC) =/\>1,000/ul; b) Platelets =/\>75,000/ul; c) Total bilirubin =/\< 1.5 x ULN; in patients with known Gilbert's syndrome direct bilirubin =/\<1.5 x ULN will be used as organ function criteria, instead of total bilirubin; d) AST (SGOT)/ALT (SGPT) \< 3 x ULN; e) Creatinine \<2 x ULN. 9. Negative urine or serum pregnancy test in women with childbearing potential (defined as not post-menopausal for 12 months or no previous surgical sterilization), within one week prior to initiation of treatment. 10. The effects of panitumumab on the developing fetus are unknown. For this reason, women of childbearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control) prior to study entry, for the duration of study participation, and for six months following the completion of therapy. Should a woman become pregnant while participating in this study, she should inform her treating physician immediately. 11. Patients must sign an Informed Consent and Authorization indicating that they are aware of the investigational nature of this study and the known risks involved. 12. Magnesium level =/\> lower limit of normal. Exclusion Criteria: 1. Prior anti-epidermal growth factor receptor antibody therapy (eg. panitumumab or cetuximab) or prior small molecule anti-epidermal growth factor receptor therapy (eg. erlotinib) for adenocarcinoma of the small bowel or ampulla of Vater. 2. Patients may not be receiving any other investigational agents nor have received any investigational drug 30 days prior to enrollment. 3. Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit adherence with study requirements. 4. Interstitial pneumonia or extensive and symptomatic interstitial fibrosis of the lung. 5. Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with panitumumab, breast feeding must be discontinued. 6. Age \<18 years. Because no dosing or adverse event data are currently available on the use of panitumumab in patients \<18 years of age, children are excluded from this study.