Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically or cytologically confirmed small cell lung cancer, meeting 1 of the
following criteria:

- Previously untreated metastatic or extensive disease

- Malignant pleural effusion or multifocal lung disease is considered
metastatic or extensive disease

- Prior radiotherapy allowed

- Recurrent disease

- Limited, metastatic, or extensive disease

- Relapsed after prior chemotherapy, excluding irinotecan hydrochloride

- At least 90 days since prior chemotherapy

- Measurable disease, defined as ≥ 1 unidimensionally measurable lesion ≥ 1 cm by
physical examination or radiographic techniques

- Known brain metastases allowed

PATIENT CHARACTERISTICS:

- ECOG performance status 0-2

- Life expectancy ≥ 3 months

- WBC > 3,000/mm³

- Absolute neutrophil count ≥ 1,500/mm³

- Platelet count ≥ 100,000/mm³

- Hemoglobin ≥ 9.0 g/dL

- Bilirubin ≤ 1.5 mg/dL

- SGOT ≤ 2.5 times upper limit of normal (ULN) (5 times ULN if liver metastases
present)

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for 3 months after
completion of study treatment

- No medical disease that, in the opinion of the investigator, would preclude study
treatment

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- At least 10 days since prior radiotherapy (including brain)

- No prior irinotecan hydrochloride

- At least 2 weeks since prior and no concurrent anticonvulsants

- No concurrent radiotherapy