OBJECTIVES: I. Determine the maximum tolerated dose of gemcitabine and cisplatin that can be administered during a standard course of radiation therapy for patients with unresectable or locally recurrent pancreatic and gastric cancer. II. Describe the tolerance of gemcitabine, cisplatin, and radiation therapy in this patient population.

III. Seek preliminary evidence of the therapeutic activity of this regimen in this patient population as measured by survival.

OUTLINE: This is a dose escalation study. Patients undergo radiotherapy to the tumor and lymph nodes, followed by a decrease in radiotherapy to the tumor alone. Radiation therapy is administered for a total of 5.5 weeks.

Patients receive intravenous gemcitabine twice weekly on Tuesday and Friday over the first 3 weeks of radiotherapy. Cisplatin is administered intravenously twice weekly following gemcitabine therapy. Three patients are treated at each dose level. Dose escalation does not occur until all patients at a given dose level have completed radiotherapy and returned for a 4 week follow up. The dose limiting toxicity (DLT) is defined as the dose at which at least 2 of 6 patients experience unacceptable toxic effects. The maximum tolerated dose is defined as the dose at which no more than 1 of 6 patients experiences DLT. Patients exhibiting stable disease remain on therapy until disease progression or intolerable toxic effects. Patients experiencing toxic effects and no disease progression are retreated at a lower dose. Patients are followed every 3 months for the first 2 years then every 6 months for the next year.

PROJECTED ACCRUAL: A total of 6-30 patients will be accrued for this study within 2 years.