Post-radiation glioma in a child. Case report and review of the literature.

A case of primary brain neoplasm is reported that developed 11 years after prophylactic brain irradiation and intrathecal methotrexate (MTX) given for acute lymphocytic leukemia (ALL) at the age of 3 years. Cases of supposed postirradiation gliomas in children seem to have increased in recent years, particularly following apparently successful treatment for ALL or medulloblastoma. This increase might reflect the increased number of long-surviving cancer children and thus suggest that brain irradiation may be a potential risk factor in this population. After reviewing some general data on neurooncogenesis, two points are stressed: (1) the child's brain is particularly susceptible to the mutagenic effects of ionizing radiation owing to physiologically active postnatal glial cell proliferation, which takes place in the cerebral hemispheres, especially during myelinogenesis; (2) MTX could promote glial neoplasm by enhancing reparative glial cell proliferation. Prospective studies seem necessary to show whether or not prophylactic brain radiation in ALL plays an oncogenetic role. Nevertheless, besides recurrent leukemia, leukoencephalopathy, and radionecrosis, the remote possibility of radiation-induced glial neoplasms should always be considered in cases of children treated for leukemia who present with neurological complications.