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