DISEASE CHARACTERISTICS:

• Histologically confirmed recurrent or refractory non-Hodgkin's lymphoma

  • First relapse requires histologic confirmation of relapse
• No CNS metastases
• No lymphomatous meningitis
• Measurable disease

PATIENT CHARACTERISTICS:

Age:

• 15-75

Performance status:

• Zubrod 0-2

Life expectancy:

• At least 12 weeks

Hematopoietic:

• Unless due to lymphoma:

  • Platelet count at least 100,000/mm^3
  • Absolute granulocyte count at least 1,500/mm^3
  • Hemoglobin at least 9 g/dL

Hepatic:

• Bilirubin no greater than 1.5 mg/dL
• SGOT no greater than 3 times upper limit of normal (ULN) (no greater than 5 times ULN if liver involvement)

Renal:

• Creatinine no greater than 2.0 mg/dL
• Baseline calcium less than 12 mg/dL

Cardiovascular:

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

Other:

• No history of seizures
• No uncontrolled diabetes mellitus (i.e., random blood sugar of at least 250 mg)
• No other concurrent severe disease
• No uncontrolled infection
• HIV negative
• No psychoses
• No prior malignancy except for adequately treated basal cell or squamous cell skin cancer or in situ cancer of the cervix unless surgically treated and disease free for at least 5 years
• Not pregnant or lactating
• Effective contraception required of fertile patients

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No prior bone marrow transplantation

Chemotherapy:

• No more than 2 prior chemotherapy regimens for treatment of lymphoma
• No prior irinotecan, topotecan or aminocamptothecin
• At least 3 weeks since prior chemotherapy

Endocrine therapy:

• Not specified

Radiotherapy:

• At least 3 weeks since prior radiotherapy
• Radiotherapy that is not a part of a combined-modality therapy is counted as a regimen (see Chemotherapy)

Surgery:

• Not specified

Other:

• No phenytoin, phenobarbital, or other antiepileptic prophylaxis