How can we differentiate supratentorial tumor recurrence from postradiation imaging changes in children treated for primary malignant brain tumors?

OBJECTIVE Distinguishing tumor recurrence from therapy-induced imaging changes (TIIC) on brain MRI in children treated for primary malignant brain tumors may be challenging. The authors aimed to assess the diagnostic ability of multimodal MRI in differentiating TIIC from tumor recurrence. METHODS The authors retrospectively included children with abnormal supratentorial brain MRI findings after treatment for primary malignant brain tumors (regardless of their localization) with complete resection and radiotherapy. A total of 18 patients with TIIC and 25 patients with tumor recurrence were compared, according to structural, apparent diffusion coefficient (ADC), and arterial spin labeling (ASL) imaging data accrued over time. TIIC were defined by a new MRI scan that was stable for at least 1 year or had regressed, or by histopathology findings in specimens obtained when the anomaly was surgically treated. RESULTS The time interval between completion of radiotherapy and the appearance of abnormal brain MRI findings was significantly shorter in the TIIC group compared with the tumor recurrence group (median 6 vs 35 months; p