Temozolomide and Topotecan in Treating Patients With Primary CNS Lymphoma

Inclusion Criteria DISEASE CHARACTERISTICS: Histologically confirmed primary CNS lymphoma at initial diagnosis Measurable tumor by radiography Failed* OR is not a candidate for first-line high-dose systemic methotrexate-based chemotherapy with or without radiotherapy NOTE: *Failure is defined as relapse, progression, or failure to achieve a complete response PATIENT CHARACTERISTICS: Age 18 and over Performance status Karnofsky 50-100% Life expectancy Not specified Hematopoietic Absolute neutrophil count ≥ 1,500/mm^3 Platelet count ≥ 100,000/mm^3 Hemoglobin ≥ 9 g/dL Hepatic SGOT and SGPT ≤ 3 times upper limit of normal Bilirubin ≤ 2.0 mg/dL Renal Creatinine clearance > 40 mL/min Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception HIV negative No known allergy to temozolomide or topotecan No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer or stage I or II cancer in complete remission No other major medical illness or psychiatric impairment that would preclude study participation PRIOR CONCURRENT THERAPY: Biologic therapy No concurrent prophylactic growth factors Chemotherapy See Disease Characteristics At least 6 weeks since prior nitrosoureas At least 2 weeks since prior methotrexate Endocrine therapy Not specified Radiotherapy See Disease Characteristics Surgery Not specified Other Recovered from all prior therapy At least 4 weeks since prior non-nitrosourea cytotoxic drugs (except methotrexate) At least 4 weeks since prior systemic investigational agents At least 2 weeks since prior non-cytotoxic antitumor drugs No other concurrent antitumor therapy EXCLUSION CRITERA Patients who are pregnant or breastfeeding, or females of childbearing potential not using adequate contraception. Known allergy to temozolomide or topotecan. Severe vomiting or other inability to administer medications orally. Major medical illnesses or psychiatric impairment that in the investigator's opinion will prevent administration or completion of the protocol therapy and/or will interfere with follow-up.