Neuroimaging-detected late transient treatment-induced lesions in pediatric patients with brain tumors.

OBJECT: After the resection of brain tumors in pediatric patients, it can be difficult to differentiate recurrent tumor from treatment effects. Although late-delayed reactions are thought to be permanent, in this study the authors sought to characterize transient brain lesions (TBLs) in the late-delayed period that completely resolved without imaging or neurological sequelae.
METHODS: In a retrospective review of an institutional neuroimaging brain tumor database, 11 patients were identified who met the imaging criteria (transient T2-weighted hyperintense enhancing lesions outside of the tumor bed, which occurred after radiation and/or chemotherapy) and had undergone three-dimensional dosimetry; their radiographic, clinical, and radiation-dosimetry results were analyzed. In the 11 patients who had been treated with multiple protocols 17 loci of abnormality, including 43 discrete, asymptomatic TBLs, were detected. The median TBL diameter was 1 cm or smaller, without mass effect or necrosis, and occurred 10 months after radiation therapy, 11 months after chemotherapy, resolved by 3 months, and occurred within the high-dose radiation treatment volume (median 55.8 Gy). The findings from extended follow up revealed the development of additional permanent complications of radiation therapy within the radiation port in five of the 11 patients.
CONCLUSIONS: A benign form of treatment-induced brain injury in children, TBLs should be treated using short-interval follow up. When these lesions are identified as a result of their characteristic imaging features, location, and temporal course, TBLs may be clearly distinguished from recurrent tumor or radiation necrosis and do not require biopsy. Further studies are needed to determine whether patients with TBLs are at an increased risk of developing more severe treatment-related brain injury.