DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed extensive stage small cell lung carcinoma (SCLC)
• No prior chemotherapy for SCLC OR
• No chemotherapy within 5 years of diagnosis of SCLC
• Prior radiotherapy to measurable or nonmeasurable disease field allowed provided radiotherapy was completed at least 6 weeks ago and the disease is demonstrated to be progressing

• No clinical signs or symptoms of brain and/or leptomeningeal metastases by CT scan or MRI

  • Brain and/or leptomeningeal metastases that are asymptomatic on neurologic exam are allowed provided metastases do not require corticosteroid therapy to control symptoms

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• ECOG 0-2

Life expectancy:

• At least 3 months

Hematopoietic:

• Hemoglobin at least 9.0 g/dL
• WBC at least 3,500/mm3
• Platelet count at least 100,000/mm3
• Neutrophil count at least 1,500/mm3

Hepatic:

• Bilirubin no greater than 2.0 mg/dL
• SGOT and SGPT no greater than 2 times the upper limit of normal (ULN) (5 times ULN if liver metastases present)
• Alkaline phosphatase no greater than 2 times ULN (5 times ULN if liver metastases present)

Renal:

• Creatinine no greater than 1.5 mg/dL
• Creatinine clearance at least 60 mL/min
• No pre-existing renal impairment that would preclude cisplatin use

Gastrointestinal:

• No clinical evidence of any gastrointestinal (GI) conditions including:

  • Removal of a portion of the stomach
  • History of recent obstruction of the GI tract
  • GI autonomic neuropathy
  • Ulcerative colitis
  • Crohn's disease
  • Malabsorption syndrome
  • Treatment with cyclosporine that would alter absorption or GI motility
• No other conditions that would preclude absorption of oral topotecan

Other:

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception for 3 months prior to study, during, and for at least 1 month after study
• No active infection
• No other prior or concurrent malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or localized low-grade prostate cancer
• No other concurrent severe medical problems that would expose the patient to extreme risk or preclude study compliance
• No prior allergic reactions to compounds chemically related to study drugs
• No pre-existing hearing impairment that would preclude cisplatin use
• No overall medical condition for which study drugs would be inappropriate

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No concurrent immunotherapy for SCLC

Chemotherapy:

• See Disease Characteristics
• No other concurrent chemotherapy for SCLC

Endocrine therapy:

• See Disease Characteristics
• No concurrent hormonal therapy for SCLC

Radiotherapy:

• See Disease Characteristics
• At least 24 hours since prior radiotherapy with no expected bone marrow suppression
• Recovered from prior palliative radiotherapy (e.g, nausea and vomiting from radiation of the epigastrium)
• No concurrent radiotherapy for SCLC
• No concurrent radiotherapy for palliation of bone metastases or CNS lesions unless approved by the investigator

Surgery:

• At least 3 weeks since prior major surgery (a shorter period is allowed if deemed in the best interest of the patient)

Other:

• More than 30 days or 5 half-lives (whichever is longer) since prior investigational drugs
• No other concurrent investigational therapy for SCLC
• No concurrent cyclosporine
• No concurrent drugs that would preclude absorption of oral topotecan