Erlotinib in Treating Patients With Locally Advanced or Metastatic Stomach Cancer or Gastroesophageal Junction Cancer

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed adenocarcinoma of the stomach\* or gastroesophageal (GE) junction * GE junction tumors include esophageal tumors arising 5 cm from the anatomic GE junction or in the gastric cardia * Locally advanced (i.e., unresectable) or metastatic disease NOTE: \*Gastric stratum temporarily closed to accrual as of 03/01/2003 * Unidimensionally measurable disease * Target lesion must not be in previously irradiated field unless there is documentation of clear progression * No known brain metastases PATIENT CHARACTERISTICS: Age: * Not specified Performance status: * Zubrod 0-1 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 1.5 times upper limit of normal (ULN) * SGOT or SGPT no greater than 1.5 times ULN (5 times ULN if liver metastases present) Renal: * Creatinine no greater than 2 times ULN Cardiovascular: * No recent myocardial infarction * No unstable angina * No life-threatening arrhythmia Gastrointestinal: * No gastrointestinal tract disease resulting in an inability to take oral medication or a requirement for IV alimentation * No active peptic ulcer disease * Must be able to swallow and/or receive enteral medications via gastrostomy feeding tube * No intractable nausea or vomiting Ophthalmic: * No history of corneal disease, including: * Dry eye syndrome or Sjögren's syndrome * Keratoconjunctivitis sicca * Exposure keratopathy * Fuch's dystrophy * Other active disorders of the cornea Other: * HIV negative * No active or uncontrolled infection * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or adequately treated stage I or II cancer currently in complete remission * No severe psychiatric disorders * Not pregnant or nursing * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * No prior biologic therapy * No concurrent anticancer immunotherapy Chemotherapy: * No prior chemotherapy for advanced or metastatic gastric cancer * At least 8 weeks since prior adjuvant chemotherapy or chemotherapy given as a radiosensitizer and recovered * No concurrent anticancer chemotherapy Endocrine therapy: * No concurrent anticancer hormonal therapy Radiotherapy: * See Disease Characteristics * At least 4 weeks since prior radiotherapy and recovered * No concurrent anticancer radiotherapy Surgery: * At least 4 weeks since prior surgical procedure for stomach\* or GE cancer and recovered * No prior surgical procedures that would affect absorption NOTE: \*Gastric stratum temporarily closed to accrual as of 03/01/2003 Other: * No prior investigational drugs * No concurrent combination antiretroviral therapy for HIV-positive patients * No other concurrent anticancer therapy