Erlotinib and Gemcitabine With or Without Panitumumab in Treating Patients With Metastatic Pancreatic Cancer

DISEASE CHARACTERISTICS:

* Histologically or cytologically confirmed adenocarcinoma of the pancreas (ductal or undifferentiated)

  * Metastatic disease
* No islet cell, acinar cell, or cystadenocarcinomas
* No locally advanced disease
* No history or known presence of CNS metastases

PATIENT CHARACTERISTICS:

* ECOG performance status 0-1
* Life expectancy ≥ 3 months
* ANC ≥ 1,500/mm\^3
* Platelet count ≥ 100,000/mm\^3
* Total bilirubin ≤ 2 times upper limit of normal (ULN) (patients may be stented)
* AST ≤ 2.5 times ULN
* Creatinine ≤ 2.0 times ULN
* Magnesium ≥ lower limit of normal
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception
* Willing to provide a stool specimen
* No malignancy diagnosed within the past 3 years except basal cell or squamous cell skin cancer, prostate cancer (Gleason \< 7), or carcinoma in situ of the cervix
* No uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, or psychiatric illness/social situations that would limit compliance with study requirements
* No clinically significant cardiovascular disease (i.e., myocardial infarction, unstable angina, symptomatic congestive heart failure, or serious uncontrolled cardiac arrhythmia) within the past year
* No known positive test(s) for HIV infection, hepatitis C virus, or acute or chronic active hepatitis B infection
* No liver dysfunction from cirrhosis or viral hepatitis
* No enteral hyperalimentation
* No grapefruit or grapefruit juice during the study

PRIOR CONCURRENT THERAPY:

* Recovered from prior therapy
* More than 4 months since prior radiotherapy, immunotherapy, or biologic therapy
* More than 4 weeks since prior and no elective or planned major surgery
* More than 2 weeks since prior minor and no elective or planned surgery
* No prior cytotoxic chemotherapy for metastatic disease

  * Adjuvant chemotherapy for completely resected disease or chemoradiotherapy for locally advanced disease is allowed, provided it was administered \> 6 months prior to study entry

    * Adjuvant chemotherapy must not have contained an EGFR inhibitor
  * Gemcitabine hydrochloride used as either a radiosensitizer or as maintenance therapy is allowed, provided more than 6 months have elapsed since the last day of treatment
* No prior anti-EGFR antibody therapy (e.g., cetuximab) or treatment with small molecule EGFR inhibitors (e.g., gefitinib hydrochloride, erlotinib hydrochloride, or lapatinib)
* No concurrent immunotherapy or radiotherapy
* No other concurrent chemotherapy
* No concurrent colony-stimulating factors during the first course of study therapy