DISEASE CHARACTERISTICS: Histologically confirmed hepatocellular carcinoma with or without evidence of unresectable extrahepatic metastasis Previously untreated disease OR Progressive disease after first line chemotherapy Bidimensionally measurable disease by CT scan, chest x-ray, or MRI of the abdomen No brain metastases

PATIENT CHARACTERISTICS: Age: 16 and over Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 80,000/mm3 Hemoglobin at least 9.0 g/dL Hepatic: Bilirubin no greater than 2.0 mg/dL Albumin at least 2.8 g/dL SGOT/SGPT no greater than 5 times upper limit of normal (ULN) PT/INR no greater than 1.5 times ULN if not on coumadin therapy Renal: Creatinine no greater than 1.5 mg/dL Cardiovascular: No active congestive heart failure No uncontrolled angina No myocardial infarction within the past 6 months Other: No concurrent serious infection No other life threatening illness No overt psychosis or mental disability that would preclude informed consent No other malignancy within the past 5 years except curatively treated nonmelanomatous skin cancer or carcinoma in situ of the cervix Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception 1 month prior to and during the study

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic therapy Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy and recovered No prior camptothecin analogues No other concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy and recovered No concurrent radiotherapy Surgery: At least 4 weeks since prior major surgery and recovered No concurrent surgery Other: No other concurrent anticancer therapy At least 4 weeks since prior investigational drugs (including analgesics or antiemetics) No other investigational drugs during or within 28 days after final dose of study drug