Cytochlor, Tetrahydrouridine, and External-Beam Radiation Therapy in Treating Patients With Cancer That Has Spread to the Brain

DISEASE CHARACTERISTICS: * Diagnosis of metastatic cancer to the brain by contrast-enhanced MRI or CT scan * Eligible for whole-brain radiotherapy (WBRT) * Patients treated with prior surgery are eligible if WBRT is to be used post operatively * Not planning to be treated with stereotactic radiosurgery * No leptomeningeal metastasis documented by contrast-enhanced MRI/CT scan or cerebrospinal fluid evaluation PATIENT CHARACTERISTICS: Inclusion criteria: * Karnofsky performance status (PS) 70-100% or ECOG PS 0-1 * Leukocytes ≥ 3,000/µL * Absolute neutrophil count \> 1,500/µL * Platelet count \> 100,000/µL * Total bilirubin normal * AST and ALT \< 2.5 times upper limit of normal * Creatinine normal OR creatinine clearance \> 60 mL/min * Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control) prior to study entry and for the duration of study participation Exclusion criteria: * Uncontrolled intercurrent illness including, but not limited to, any of the following: * Ongoing or active infection * Symptomatic congestive heart failure * Unstable angina pectoris * Cardiac arrhythmia * Psychiatric illness/social situations that would limit compliance with study requirements * Pregnant or lactating * Alcohol dependence PRIOR CONCURRENT THERAPY: * No prior radiotherapy to the brain * No concurrent combination antiretroviral therapy for HIV-positive patients * No other concurrent chemotherapy, immunotherapy, hormonal therapy (excluding contraceptives and replacement steroids), or other experimental medication * No other concurrent anticancer therapy outside the protocol * Systemic therapy one month before or after brain radiotherapy is allowed * No concurrent heparin or coumadin