Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed metastatic or surgically unresectable solid tumor, having
received the following maximum number of prior therapies for advanced disease:

- Bladder cancer - no more than 1 prior therapy

- Breast cancer - no more than 2 prior therapies

- Colorectal cancer - no more than 1 prior therapy

- Kidney cancer - no prior therapy

- Lung cancer - no more than 1 prior therapy

- Pancreatic cancer - no prior therapy

- Bidimensionally measurable disease outside a previously irradiated field

- At least 2 cm x 2 cm

- No known bone metastases

- CNS involvement allowed if successfully controlled by surgery or radiotherapy and not
requiring corticosteroids

- Hormone receptor status:

- Not specified

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Menopausal status:

- Not specified

Performance status:

- ECOG 0-2

Life expectancy:

- At least 3 months

Hematopoietic:

- Granulocyte count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

Hepatic:

- Bilirubin no greater than 1.5 mg/dL regardless of liver involvement secondary to
tumor

- SGOT no greater than 3 times upper limit of normal (ULN) (no greater than 5 times ULN
if liver metastases present)

- No known Gilbert's disease

Renal:

- Creatinine no greater than 1.8 mg/dL

- Calcium less than 12.0 mg/dL

Cardiovascular:

- No myocardial infarction within the past 6 months

- No congestive heart failure requiring therapy

Other:

- No active uncontrolled bacterial, viral (including HIV), or invasive fungal infection

- No psychiatric disorders that would prevent compliance

- No other malignancy within the past 5 years except adequately treated basal or
squamous cell skin cancer or carcinoma in situ of the cervix

- No history of seizures

- Not pregnant or nursing

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- No concurrent sargramostim (GM-CSF)

- No concurrent immunotherapy

Chemotherapy:

- No prior irinotecan, topotecan, or gemcitabine

- Prior adjuvant chemotherapy allowed, if at least 1 year between last dose of adjuvant
chemotherapy and recurrence of cancer

- No other concurrent chemotherapy

Endocrine therapy:

- Not specified

Radiotherapy:

- See Disease Characteristics

- At least 4 weeks since prior radiotherapy to less than 30% of bone marrow

- No prior whole pelvic radiotherapy

- No concurrent radiotherapy

Surgery:

- See Disease Characteristics

Other:

- No concurrent phenytoin, phenobarbital, or other antiepileptic prophylaxis