Two metachronous tumors induced by radiation therapy: case report and review of the literature.

Various radiation-induced tumors, including meningioma, glioma, and sarcoma, have been reported; however, metachronous intracranial double tumors induced by radiation therapy are extremely rare. A 1-year-old boy had undergone tumor removal and craniospinal radiation therapy (30 Gy) for cerebellar medulloblastoma. At 24 years old, parasagittal meningioma developed in the left parietal region and was totally removed. Six years later, an infiltrative tumor was newly found in the right fronto-temporal white matter. The patient underwent stereotactic biopsy, and the tumor was found to be an anaplastic astrocytoma. Chromosomal analysis by fluorescence in situ hybridization (FISH) revealed loss of heterozygosity (LOH) of 1p. As the patient had previously had craniospinal irradiation, no additional radiation therapy was delivered. He underwent chemotherapy with temozolomide and the disease is now stable. Since both secondary tumors were located within the area of previous radiation and the patient did not have any genetic disease predisposing him to tumors, radiation therapy was considered to be responsible for their tumorigenesis. To our knowledge, this case is the fourth case of radiation-induced double CNS tumors arising after radiotherapy to be described in the literature. Whenever radiation is administered to children or young adults, careful serial screening studies are needed.