DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed relapsed or refractory non-small cell lung carcinoma (NSCLC)

  • Squamous cell carcinoma
  • Basaloid carcinoma
  • Adenocarcinoma
  • Bronchoalveolar carcinoma
  • Adenosquamous cell carcinoma
  • Large cell carcinoma
  • Large cell neuroendocrine carcinoma
  • Giant cell carcinoma
  • Sarcomatoid carcinoma
  • Non-small cell carcinoma not otherwise specified
• Histologic or cytologic documentation of recurrence required if disease previously completely resected
• Must have had only 1 prior chemotherapy regimen, including adjuvant or neoadjuvant therapy for NSCLC

• At least 1 unidimensionally measurable lesion

  • At least 20 mm with conventional techniques OR
  • At least 10 mm with spiral CT scan

  • Lesions that are not considered measurable include the following:

    • Bone lesions
    • Leptomeningeal disease
    • Ascites
    • Pleural/pericardial effusion
    • Abdominal masses not confirmed and followed by imaging techniques
    • Cystic lesions
    • Tumor lesions in a previously irradiated area
• Controlled CNS metastases allowed if patient is neurologically stable and off steroids

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• ECOG 0-1

Life expectancy:

• Not specified

Hematopoietic:

• Granulocyte count at least 1,500/mm3
• Platelet count at least 100,000/mm3

Hepatic:

• Bilirubin no greater than 1.5 mg/dL

Renal:

• Creatinine no greater than upper limit of normal

Other:

• Not pregnant or nursing
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• Not specified

Chemotherapy:

• See Disease Characteristics
• At least 4 weeks since prior chemotherapy (6 weeks for mitomycin)
• No prior irinotecan or other camptothecin drug
• No other concurrent chemotherapy

Endocrine therapy:

• See Disease Characteristics
• No concurrent hormonal therapy except for non-cancer-related conditions (e.g., insulin for diabetes)
• No concurrent steroids except for adrenal failure

Radiotherapy:

• See Disease Characteristics
• Prior radiotherapy for symptomatic lesions or those that might produce disability (e.g., painful bone metastases) allowed if other measurable disease present
• At least 4 weeks since prior radiotherapy
• No concurrent palliative radiotherapy

Surgery:

• See Disease Characteristics