DISEASE CHARACTERISTICS: Diagnosis of one of the following advanced malignancies: Breast Colorectal Non-small cell lung Gastric Pancreatic Renal Prostate Myeloma Failed standard therapy OR No effective standard therapy exists Measurable or evaluable disease No known CNS metastases Hormone receptor status: Not specified

PATIENT CHARACTERISTICS: Age: 18 and over Sex: Male or female Menopausal status: Not specified Performance status: Karnofsky 60-100% Life expectancy: Not specified Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9 g/dL Hepatic: Bilirubin no greater than 2.0 mg/dL AST and ALT no greater than 3 times upper limit of normal Renal: Creatinine no greater than 2 mg/dL OR Creatinine clearance at least 40 mL/min Cardiovascular: No myocardial infarction or severe/unstable angina within the past 6 months No evidence of uncompensated coronary artery disease by electrocardiogram or physical exam Other: No other malignancy within the past 5 years except basal cell skin cancer or carcinoma in situ of the cervix No insulin-dependent diabetes mellitus No non-insulin-dependent diabetes mellitus with clinical evidence of severe peripheral vascular disease or diabetic ulcers No manifestation of malabsorption due to prior surgery, GI disease, or unknown reasons No active inflammatory bowel disease No known intolerance to any excipients in the study drug formulation No other acute or chronic medical or psychiatric condition or laboratory abnormality that would preclude study Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior anticancer biologic or immunotherapy and recovered No prior SU006668 No other concurrent immunotherapy Chemotherapy: At least 4 weeks since prior anticancer chemotherapy (6 weeks for nitrosoureas or mitomycin) and recovered No concurrent chemotherapy Endocrine therapy: At least 4 weeks since prior hormonal therapy No concurrent hormonal therapy except for hormonal contraception or appetite stimulation Radiotherapy: Recovered from prior radiotherapy Surgery: At least 6 weeks since prior surgery At least 6 months since prior coronary/peripheral artery bypass graft surgery Prior major GI surgery allowed if no residual syptomatic manifestation of malabsorption No prior organ transplantation Other: At least 4 weeks since prior investigational agents No other concurrent investigational agents