DISEASE CHARACTERISTICS:

• Histologically proven metastatic or unresectable high grade neuroendocrine tumor including:

  • Small cell carcinoma
  • Large cell neuroendocrine carcinoma
  • Other high grade neuroendocrine carcinomas without specification to cell size
  • No lung only involvement without any other primary site
• No primary small cell lung cancer with or without metastases
• Bidimensionally measurable disease with at least one lesion measuring at least 1 cm by 1 cm

• High grade tumor indicated by at least one of the following:

  • Growth pattern suggestive of neuroendocrine differentiation
  • Mitotic rate greater than 15 mitoses per 10 hpf
  • Presence of abundant necrosis
• Immunohistochemical evidence of neuroendocrine differentiation by positive staining for chromogranin, synaptophysin, or neuron specific enolase if no classic microscopic appearance of small cell carcinoma
• No low grade neuroendocrine tumors (e.g., carcinoid tumors, pancreatic endocrine tumors) and atypical tumors

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• Karnofsky 70-100%

Life expectancy:

• Not specified

Hematopoietic:

• WBC at least 3,500/mm^3
• Granulocyte count at least 1,500/mm^3
• Platelet count at least 75,000/mm^3

Hepatic:

• Bilirubin no greater than upper limit of normal (ULN)
• SGOT no greater than 5 times ULN

Renal:

• Creatinine no greater than 2.0 mg/dL

Cardiovascular:

• No myocardial infarction within the past 6 months
• No uncontrolled congestive heart failure requiring therapy

Other:

• No active or uncontrolled infection
• HIV negative
• No psychiatric or other disorder that would preclude study
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• No more than 2 prior chemotherapy regimens
• No prior camptothecins

Endocrine therapy

• Not specified

Radiotherapy

• Not specified

Surgery

• Not specified