Carbon C 14 Oxaliplatin Microdosing Assay in Predicting Exposure and Sensitivity to Oxaliplatin-Based Chemotherapy in Patients with Colon, Rectal, Pancreatic, Gastroesophageal, Appendix, or Small Intestine Cancer

Inclusion Criteria

• Histologically or cytologically confirmed colon, rectal, pancreatic, gastroesophageal, appendiceal, or small bowel adenocarcinoma
• Intent to treat the patient with a leucovorin calcium, fluorouracil, and oxaliplatin (FOLFOX) chemotherapy regimen containing fluorouracil (5-FU), leucovorin, and oxaliplatin according to clinical standard practice; the intent should be to dose oxaliplatin at 85 mg/m^2 on an every 2 week basis
• Treatment with any additional Food and Drug Administration (FDA)-approved biologic agent (i.e. bevacizumab, cetuximab, or panitumumab) is allowed according to standard practice
• Prior radiation or surgery is allowed, but should be finished at least 2 weeks prior to study enrollment
• Any number of prior therapies other than oxaliplatin is allowed
• Zubrod performance status equal to or less than 2 (Karnofsky equal to or greater than 50%)
• Life expectancy of at least 3 months
• Absolute neutrophil count greater than or equal to 1,500/microL
• Platelets greater than or equal to 100,000/microL
• Total bilirubin less than 3 x institutional upper limit of normal (ULN)
• Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase [SGOT]) less than or equal to 5 x ULN
• Creatinine less than 1.5 x ULN
• Women of child bearing potential must not be pregnant; a pre-study pregnancy test must be negative
• Women of child-bearing potential must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for 30 days after study participation
• Men must agree to use adequate contraception (barrier method or abstinence) prior to study entry and for 30 days after study participation
• Ability to understand and willing to sign a written informed consent document

Exclusion Criteria

• Prior treatment with oxaliplatin
• Patients must not receive concomitant radiation
• 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 compliance with study requirements
• Participants who are pregnant or nursing
• Participants who are allergic to any platinum agent
• Participants who have more than grade 1 peripheral neuropathy