Irinotecan and Whole-Brain Radiation Therapy in Treating Patients With Brain Metastases From Solid Tumors

DISEASE CHARACTERISTICS: * Diagnosis of brain metastasis from a histologically confirmed solid tumor, meeting the following criteria: * Must have histologic proof of original malignancy * No germ cell tumor metastasis * Biopsy-proven brain metastasis preferred when clinical history and radiographic findings are equivocal * At least 1 unidimensionally measurable lesion ≥ 50 mm by head contrast CT scan and/or brain MRI * Patients enrolled in the phase II portion of the study must meet the following Radiation Therapy Oncology Group Recursive Partitioning Analysis staging criteria for brain metastases: * Class II classification * Zubrod performance status 0-1 AND any of the following: * Age \> 65 years * Extracranial metastasis * Uncontrolled primary malignancy PATIENT CHARACTERISTICS: * Zubrod performance status 0-1 * Life expectancy ≥ 3 months * Able to participate in the Mini-Mental Status Examination * WBC ≥ 3,000/mm³ * Absolute neutrophil count ≥ 1,500/mm³ * Platelet count ≥ 100,000/mm³ * Bilirubin ≤ 1.5 mg/dL * AST ≤ 2.5 times upper limit of normal (ULN) (5 times ULN if liver metastases are present) * Hemoglobin ≥ 9.0 g/dL * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No concurrent medical disease that, in the investigator's opinion, would preclude study participation PRIOR CONCURRENT THERAPY: * More than 21 days since prior chemotherapy * No prior whole-brain radiotherapy * N…