Temozolomide Plus PEG-Interferon Alfa-2B in Treating Patients With Advanced Solid Tumors

DISEASE CHARACTERISTICS: * Histologically confirmed advanced solid tumor that is refractory to standard therapy OR * Histologically confirmed chemotherapy-naive advanced cancer for which no curative therapy or higher priority palliative chemotherapy exists * Brain metastasis allowed * No bone marrow involvement of tumor 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 AND/OR * Platelet count greater than 100,000/mm\^3 Hepatic: * ALT or AST less than 3 times upper limit of normal (ULN) (5 times ULN if liver metastases present) * No autoimmune hepatitis Renal: * Creatinine less than 2.5 times ULN Cardiovascular: * No severe coronary artery disease * No congestive heart failure Pulmonary: * No severe chronic obstructive pulmonary disease Gastrointestinal: * No frequent vomiting * No medical condition that would interfere with oral medication intake (e.g., partial bowel obstruction, partial intestinal bypass, or external biliary diversion) Other: * No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix * No known or suspected hypersensitivity to imidazotetrazin, interferon alfa, or any excipient or vehicle included in the formulation or delivery system of study drug * No history of autoimmune disease * No preexisting severe psychiatric condition or history of severe psychiatric disorder (including suicidal ideation or attempt) * No life-threatening condition or severe preexisting condition * No uncontrolled thyroid abnormalities * No nonmalignant systemic disease * No active uncontrolled infection * HIV negative * No AIDS-related illness * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception PRIOR CONCURRENT THERAPY: Biologic therapy: * At least 3 weeks since prior biologic agents (e.g., bi-specific antibodies, interleukin-2, or interferon) and recovered (excluding alopecia) * No prior allogeneic, syngeneic, or autologous bone marrow or stem cell transplantation * No other concurrent biologic therapy * No concurrent colony stimulating factors or epoetin alfa for the prevention of myelotoxicity Chemotherapy: * See Disease Characteristics * At least 4 weeks since prior chemotherapy (more than 6 weeks for nitrosoureas, melphalan, or mitomycin) and recovered (excluding alopecia) * No prior high-dose chemotherapy and stem cell transplantation * No more than 3 prior chemotherapy regimens * No other concurrent chemotherapy Endocrine therapy: * Not specified Radiotherapy: * At least 6 weeks since prior wide-field radiotherapy to at least 25% of bone marrow (e.g., pelvic radiotherapy) * More than 6 weeks since prior strontium chloride Sr 89 or samarium Sm 153 lexidronam pentasodium * Recovered from prior radiotherapy (excluding alopecia) * No concurrent radiotherapy Surgery: * At least 4 weeks since prior major surgery * At least 1 week since prior minor surgery Other: * At least 4 weeks since prior investigational therapy