DISEASE CHARACTERISTICS:

• Histologically or cytologically confirmed advanced solid tumor that is not amenable to any clinical improvement by current standard treatments

  • No tumors of the upper digestive tract
• No clinical signs of CNS involvement

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• ECOG 0-2 OR
• WHO 0-2

Life expectancy:

• At least 12 weeks

Hematopoietic:

• WBC at least 3,000/mm^3
• Neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10.0 g/dL

Hepatic:

• Bilirubin no greater than 1.5 times upper limit of normal (ULN)
• AST and ALT no greater than 2.5 times ULN
• No unstable hepatobiliary disease that would preclude study

Renal:

• Creatinine no greater than 1.5 times ULN
• No unstable renal disease that would preclude study

Cardiovascular:

• No unstable cardiovascular disease (e.g., stroke) that would preclude study

Pulmonary:

• No unstable pulmonary disease that would preclude study

Gastrointestinal:

• No digestive disease, including upper gastrointestinal tract, that would hamper absorption
• No evident/known lactose malabsorption

Other:

• No allergy to components of the study drug
• No uncontrolled infection
• No other unstable systemic disease that would preclude study
• No psychological, familial, sociological, or geographical condition that would preclude compliance
• Not pregnant
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 3 months after study

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 4 weeks since prior anticancer biologic therapy

Chemotherapy:

• At least 4 weeks since prior anticancer chemotherapy

Endocrine therapy:

• Prior anticancer hormonal therapy allowed

Radiotherapy:

• At least 6 weeks since prior radiotherapy
• No concurrent radiotherapy

Surgery:

• At least 2 weeks since prior surgery

Other:

• At least 4 weeks since other prior anticancer treatment
• No other concurrent anticancer agents or investigational therapy