Inclusion Criteria

DISEASE CHARACTERISTICS:

- Pathologically proven advanced cancer for which no curative therapy exists

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- ECOG 0-2

Life expectancy:

- Not specified

Hematopoietic:

- Absolute neutrophil count greater than 1,500/mm^3

- Platelet count greater than 100,000/mm^3

- Hemoglobin greater than 9 g/dL

Hepatic:

- Bilirubin normal

- SGOT and SGPT no greater than 2 times upper limit of normal (ULN) (no greater than 5
times ULN if liver metastases present)

Renal:

- Creatinine normal

Other:

- Unassisted oral or enteral intake sufficient to maintain a reasonable state of
nutrition

- No concurrent medical condition that is likely to interfere with study participation

- No active visual disturbances that require intervention beyond corrective lenses

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- No prior bone marrow transplantation

- No concurrent immunotherapy

Chemotherapy:

- At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin)

- No prior high dose chemotherapy with bone marrow or stem cell rescue

- No other concurrent chemotherapy

Endocrine therapy:

- No concurrent hormone therapy (except megestrol acetate)

Radiotherapy:

- At least 4 weeks since prior radiotherapy

- No prior radiotherapy to 25% or more of bone marrow

- No concurrent radiotherapy (except palliative radiotherapy within the first 28 days
of the study)

Surgery:

- Not specified

Other:

- At least 30 days since prior investigational therapy

- No concurrent investigational therapy