DISEASE CHARACTERISTICS:

• Diagnosis of cancer that has failed standard therapy or for which no such therapy exists, including, but not limited to:

  • Unresectable primary or recurrent solid tumors (e.g., colon, pancreatic, lung, esophageal, or cholangiocarcinoma)
  • Metastatic disease
  • Lymphoma with no prior high-dose chemotherapy requiring autologous or allogeneic stem cell rescue
• No leukemias
• No CNS metastases or primary CNS malignancies
• No failure on prior gemcitabine therapy

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• ECOG 0-2

Life expectancy:

• Not specified

Hematopoietic:

• Absolute granulocyte count at least 2,000/mm^3
• Platelet count at least 100,000/mm^3

Hepatic:

• Bilirubin no greater than 2.0 mg/dL
• Transaminases less than 6 times upper limit of normal

Renal:

• Creatinine no greater than 2.0 mg/dL

Other:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• No other serious concurrent medical illness that would preclude study
• No active infections requiring IV antibiotics
• HIV negative

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• See Disease Characteristics
• More than 4 weeks since prior immunotherapy and recovered

Chemotherapy:

• See Disease Characteristics
• More than 4 weeks since prior chemotherapy (at least 6 weeks for mitomycin or nitrosoureas) and recovered
• At least 3 months since prior suramin
• At least 5 weeks since prior eniluracil (8 weeks prior to start of fluorouracil) and recovered

Endocrine therapy:

• No steroid therapy if utilized for chronic lymphoma therapy
• At least 4 weeks since prior steroidal therapy as disease treatment

Radiotherapy:

• At least 2 weeks since prior radiotherapy to no more than 20% of bone marrow
• At least 4 weeks since prior radiotherapy to 21% or more of bone marrow
• Recovered from prior radiotherapy

Surgery:

• Recovered from prior surgery

Other:

• No concurrent cimetidine