Erlotinib Combined With Gemcitabine in Treating Patients With Newly Diagnosed Locally Advanced or Metastatic Pancreatic Cancer or Other Solid Tumors

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed locally advanced or metastatic epithelial carcinoma of the pancreas or other malignancy considered to be potentially responsive to gemcitabine * Newly diagnosed or gemcitabine naive * Measurable or evaluable disease * Not amenable to surgical intervention due to medical contraindications or non-resectability of the tumor * No islet cell tumors or other non-epithelial cell carcinomas of the pancreas * No active CNS metastases or leptomeningeal disease * Treated or asymptomatic brain metastases are allowed if on a stable dose of corticosteroids and/or there is no change in brain disease status for at least 4 weeks after related therapy (e.g., whole-brain radiotherapy) PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Karnofsky 70-100% Life expectancy: * Not specified Hematopoietic: * Absolute neutrophil count at least 1,500/mm\^3 * Platelet count at least 100,000/mm\^3 Hepatic: * Bilirubin no greater than 2.0 mg/dL (except for documented Gilbert's syndrome) * AST or ALT less than 2 times upper limit of normal (ULN) (no greater than 5 times ULN if hepatic obstruction or metastases present) * Albumin at least 2.5 g/dL Renal: * Creatinine less than 1.5 times ULN OR * Creatinine clearance at least 60 mL/min Cardiovascular: * No significant cardiovascular disease * No history of congestive heart failure currently requiring therapy * No ventricular arrhythmia requiring anti-arrhythmic therapy * No severe conduction disturbances * No angina pectoris requiring therapy * No myocardial infarction within the past 6 months Gastrointestinal: * No significant gastrointestinal abnormalities including: * Requirement for IV alimentation * Active peptic ulcer disease Ophthalmic: * No significant ophthalmologic abnormalities including: * Severe dry eye syndrome * Keratoconjunctivitis sicca * Sjogren's syndrome * Severe exposure keratopathy * Disorders that would increase the risk for epithelium-related complications (e.g., bullous keratopathy, aniridia, severe chemical burns, or neutrophilic keratitis) * Abnormal Schirmer test (less than 2 mm) allowed provided there is no evidence of clinically significant corneal surface abnormalities Other: * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No known or suspected hypersensitivity to gemcitabine * No uncontrolled infection * HIV negative * No other malignancy within the past 5 years except treated non-melanoma skin cancer or carcinoma in situ of the breast or cervix * No other life-threatening illness * No psychiatric disorders or altered mental status the would preclude informed consent or study PRIOR CONCURRENT THERAPY: Biologic therapy: * At least 28 days since prior immunotherapy or biological response modified therapy for the primary malignancy * No concurrent immunotherapy or biologic response modifier therapy for the primary malignancy Chemotherapy: * See Disease Characteristics * At least 28 days since prior chemotherapy for the primary malignancy * No prior mitomycin or nitrosoureas for the primary malignancy * No more than 6 prior courses of chemotherapy with an alkylating agent for the primary malignancy * No prior gemcitabine for the primary malignancy except as a low-dose (less than 500 mg/m\^2) radiosensitizer administered concurrently with or within 2 weeks after radiotherapy at least 3 months ago * No other concurrent chemotherapy for the primary malignancy Endocrine therapy: * See Disease Characteristics * At least 28 days since prior systemic hormonal therapy (except LH-RH agonists) for the primary malignancy * No concurrent systemic hormonal therapy (except LH-RH agonists) for the primary malignancy * Other concurrent endocrine therapy is allowed as follows: * Hormonal therapy (e.g., megestrol) for appetite stimulation * Nasal, ophthalmic, or topical glucocorticoids * Oral glucocorticoids for adrenal insufficiency * Low-dose maintenance steroids Radiotherapy: * See Disease Characteristics * At least 28 days since prior radiotherapy for the primary malignancy or metastases and recovered * No prior wide-field radiotherapy to 25% or more of marrow-bearing bone * No prior pelvic irradiation * No concurrent radiotherapy for the primary malignancy or metastases * No concurrent wide-field radiotherapy for pain management Surgery: * See Disease Characteristics * Recovered from any prior surgery * No prior surgical procedures affecting absorption Other: * No prior agent for the primary malignancy targeting the epidermal growth factor receptor (EGFR) or EGFR-specific tyrosine kinase activity