Inclusion Criteria

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