Descriptive Analysis of Surgically Resected Pure Radiation Necrosis After Radiation Therapy for Brain Metastasis: Clinical Features, MRI Findings, and Outcomes

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BACKGROUND: Differentiating radiation necrosis (RN) from tumor progression is challenging despite advanced neuroimaging techniques. We collected a consecutive series of surgically resected RN with presumptive diagnosis of recurrent/refractory brain metastasis (BM) after radiation therapy (RT) and performed a descriptive analysis of characteristics and clinical courses. METHODS: From 107 patients who underwent surgery to remove previously irradiated BM, we retrieved 18 patients with pathologically confirmed pure RN. RESULTS: Sixteen patients (89%) had preoperative MRI suggesting recurrent/refractory BM in accordance with clinical suspicion, and 14 (78%) patients showed radiological response after RT before progression. The median time from RT to surgery was 28.5 months (range 6-94 months). RT doses varied from 1,800 cGy/single fraction to 8,300 cGy/21 fractions. Lobulated/irregular shape, central necrosis, and substantial increase of perilesional edema were dominant MRI features. Neurological symptoms improved or stabilized in 13 patients (72%) after surgery. Five cases of distant recurrences occurred in patients with uncontrolled systemic cancer, except for one patient with controlled small cell lung cancer who recurred as a leptomeningeal metastasis. One patient had multiple enhancing lesions along the surgical cavity, suggesting local recurrence. Median overall survival after surgical removal of RN was 34 months (range 4.3-132 months), and eight out of eleven patients with controlled systemic cancer remained alive at last follow-up. CONCLUSION: RN frequently mimics recurrent BM despite advanced imaging. Surgical resection provides both definitive diagnosis and symptomatic benefit in selected patients. However, distant recurrence of BM could happen in patients with uncontrolled systemic cancer.

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