Cetuximab & Celecoxib for Metastatic Colorectal Cancer or Colorectal Cancer That Cannot Be Removed by Surgery

Inclusion Criteria: * Patients must have histologically confirmed colorectal cancer that is metastatic or unresectable and for which standard curative or palliative measures do not exist or are no longer effective. * Patients must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded) as \> or equal to 20 mm with conventional techniques or as \> or equal 10 mm with spiral CT scan. * Patients must have progressed after at least 1 chemotherapy regimen for advanced disease. No prior therapy which specifically and directly targets the EGFR pathway. * Age 18 years or older * ECOG performance status ≤ 2. * Life expectancy of greater than 3 months. * Normal organ and marrow functions as defined below: * absolute neutrophil count ≤ 1,500/μl * platelets ≤ 100,000/μl * total bilirubin within normal institutional limits * AST(SGOT)/ALT(SGPT) \> or equal to 2.5 times institutional upper limit of normal or \> or equal to 5.0 times normal if liver metastases are present * creatinine within normal institutional limits OR * creatinine clearance \> or equal to 60 mL/min/1.73 m2 for patients creatinine levels above institutional normal * The effects of cetuximab and/or celecoxib on the developing human fetus at the recommended therapeutic doses are unknown. For this reason, women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately. * Ability to understand and the willingness to provide written informed consent. Exclusion Criteria: * Patients who have had chemotherapy or radiotherapy within 4 weeks (6 weeks for nitrosoureas or mitomycin C) prior to entering the study or those who have not recovered from adverse events due to agents administered more than 4 weeks earlier. * Patients may not be receiving any other investigational agents. * Patients with known brain metastases should be excluded from this clinical trial because of their poor prognosis and because they often develop progressive neurologic dysfunction that would confound the evaluation of neurologic and other adverse events. * Prior severe infusion reaction to a monoclonal antibody * Serum calcium \>12.0 mg/dl. * Patients must be off all other selective or non-selective COX-2 inhibitors for at least 2 weeks prior to study entry (with the exception of 81 mg of daily aspirin). * No major surgery within 4 weeks. No minor surgery (laparoscopy, thoracoscopy, port placement) within 1 week. * Patients must be \> 4 weeks from prior pelvic radiation and recovered from side effects. * Patients must be \> 1 week from prior palliative radiation and have recovered from all side effects. * Prior treatment with EGFR targeting therapies. * Significant traumatic injury occurring within 28 days prior to treatment. * Gastrointestinal tract disease resulting in an inability to take oral medication or a requirement for IV alimentation, prior surgical procedures affecting absorption, or active peptic ulcer disease. * 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. * Pregnant women are excluded from this study because cetuximab is an epidermal growth factor inhibitor with the potential for teratogenic or abortifacient effects based on the data suggesting that EGFR expression is important for normal organ development. Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with cetuximab, breastfeeding should be discontinued if the mother is treated with cetuximab. * Patients with known HIV disease.