Malignant Gliomas: MR Imaging Spectrum of Radiation Therapy- and Chemotherapy-induced Necrosis of the Brain after Treatment

TLDR

The study aims to describe the MR imaging features of radiation and chemotherapy‑induced brain injury, focusing on radiation necrosis. The authors examined 148 adults who underwent tumor resection, accelerated radiation with carboplatin, and subsequent chemotherapy, with serial MR imaging every 6–8 weeks during the first year and every 3–6 months thereafter, and histopathologic confirmation of lesions. MR imaging revealed pure radiation necrosis in 20 patients, mixed necrosis with minimal tumor in 16, cranial‑nerve necrosis in 2, white‑matter enhancement in 52, and cortical enhancement in 9, illustrating distinct spatial and temporal patterns that help differentiate necrosis from tumor recurrence.

Abstract

PURPOSE: To describe both the common and less frequently encountered magnetic resonance (MR) imaging features of radiation therapy– and chemotherapy-induced brain injury, with particular emphasis on radiation necrosis. MATERIALS AND METHODS: A cohort of 148 adult patients underwent surgical resection of malignant brain (glial) tumors and were subsequently entered into a research protocol that consisted of accelerated radiation therapy with carboplatin followed by chemotherapy with procarbazine, lomustine, and vincristine. Patients typically underwent sequential MR imaging at 6–8-week intervals during the 1st year and at 3–6-month intervals during subsequent years. In all patients, histopathologic confirmation of lesion composition was performed by board-certified neuropathologists. RESULTS: The patients exhibited different types of MR imaging–detected abnormalities of the brain: pure radiation necrosis in 20 patients, a mixture of predominantly radiation necrosis with limited recurrent and/or residual tumor (less than 20% of resected tissue) in 16 patients, radiation necrosis of the cranial nerves and/or their pathways in two patients, radiation-induced enhancement of the white matter in 52 patients, and radiation-induced enhancement of the cortex in nine patients. CONCLUSION: The frequent diagnostic dilemma of recurrent neoplasm versus radiation necrosis is addressed in this study through a description of the varying spatial and temporal patterns of radiation necrosis at MR imaging.