Lapatinib Ditosylate and Capecitabine in Treating Patients With Metastatic Pancreatic Cancer

DISEASE CHARACTERISTICS:

* Histologically or cytologically confirmed metastatic adenocarcinoma of the pancreas
* Measurable or non-measurable disease

  * Measurable disease is defined as ≥ 1 lesion that can be accurately measured in ≥ 1 dimension (longest diameter to be recorded) as ≥ 20 mm with conventional techniques or as ≥ 10 mm with spiral CT scan
* No known brain metastases or leptomeningeal disease

PATIENT CHARACTERISTICS:

* ECOG performance status 0-1
* Life expectancy \> 12 weeks
* ANC ≥ 1,500/mm\^3
* Platelet count ≥ 100,000/mm\^3
* Hemoglobin ≥ 9 g/dL
* Albumin ≥ 2.5 g/dL
* Serum bilirubin ≤ 1.5 times upper limit of normal (ULN) (2.5 times ULN if Gilbert's syndrome is present)
* AST and ALT ≤ 3 times ULN (5 times ULN if documented liver metastases are present)
* Creatinine \< 1.5 times ULN
* Cardiac ejection fraction normal by ECHO or MUGA scan
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception
* Able to swallow and retain oral medication
* No gastrointestinal (GI) tract disease resulting in an inability to take oral medication, malabsorption syndrome, requirement for IV alimentation, or uncontrolled inflammatory GI disease (e.g., Crohn's disease or ulcerative colitis)
* No active hepatic or biliary disease, except for Gilbert's syndrome, asymptomatic gallstones, liver metastases, or stable chronic liver disease per investigator assessment
* No active cardiac disease within the past 6 months, including any of the following:

  * Uncontrolled angina
  * Clinically significant arrhythmia, except for asymptomatic atrial fibrillation requiring anticoagulation
  * Myocardial infarction
  * Uncontrolled or symptomatic congestive heart failure
  * Any other cardiac condition that, in the opinion of the treating physician, would make this study unreasonably hazardous for the patient
* No concurrent uncontrolled illness including, but not limited to, ongoing or active infection or psychiatric illness/social situation that would limit compliance with study requirements
* No known immediate or delayed hypersensitivity reaction or idiosyncrasy to drugs chemically related to lapatinib ditosylate or any of its excipients, capecitabine, or fluorouracil
* No known dihydropyrimidine dehydrogenase (DPD) deficiency
* No other malignancy within the past 5 years except for completely resected nonmelanoma skin cancer or successfully treated in situ carcinoma

PRIOR CONCURRENT THERAPY:

* Recovered from prior radiotherapy or surgery
* No prior surgical procedures affecting absorption
* No prior EGFR- or ErbB2-targeting therapies
* No prior capecitabine
* No prior chemotherapy for locally advanced or metastatic pancreatic cancer
* At least 3 months since prior adjuvant chemotherapy

  * Prior fluorouracil allowed as a radiosensitizer only
* More than 30 days (or 5 half-lives) since prior investigational drugs
* No concurrent radiotherapy or surgery for metastatic cancer
* No concurrent combination antiretroviral therapy for HIV-positive patients
* No concurrent CYP3A4 inducers or inhibitors
* No other concurrent investigational agents or anticancer therapy (e.g., cytotoxic or biologic therapy)
* No concurrent herbal (alternative) medicines