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SURG-04. SALVAGE RESECTION OF RECURRENT PREVIOUSLY-IRRADIATED BRAIN METASTASES: CLINICAL AND RADIOGRAPHIC OUTCOMES


 
 
 The management of brain metastasis (BrM) recurrence after stereotactic body radiotherapy (SBRT) poses a clinical challenge. The efficacy of salvage resection is undefined, and the role of adjuvant resection cavity reirradiation is unclear given the compounded risk of radiation injury.
 
 
 
 Retrospective analysis of previously-irradiated BrM that underwent resection between March 2003 and February 2020 at Memorial Sloan Kettering Cancer Center was performed. Only cases with histopathologic evidence of viable malignancy were included, and specimens were classified by the gross proportion of viable tumor versus treatment effect. Clinical and radiographic parameters were collected. Post-operative recurrence and radiation necrosis were based on RANO-BM criteria and distinguished by histopathologic, radiographic and clinical characteristics. Equivocal cases were adjudicated by a blinded neuroradiologist.
 
 
 
 One-hundred fifty-five resected recurrent BrM following SBRT in 135 patients were evaluated. Seventeen received additional prior whole-brain radiation. Metastases derived from non-small-cell lung (36.8%), melanoma (27.1%), breast (21.3%), renal (3.9%), colorectal (1.9%) and other (9.0%) primary malignancies. Forty-eight (31.0%) had only microscopic malignant disease with extensive necrosis, 44 (28.4%) had mixed or unspecified tumor with treatment effect, and 63 (40.6%) were reported as purely viable tumor by histopathologic report. Thirty-nine (25.2%) post-operative cavities underwent adjuvant reirradiation within 60 days. At 6 and 12 months, local tumor recurrence occurred in 31.6% (95% CI: 24.4%-39.1%) and 40.4% (95% CI: 32.5%-48.2%), respectively, with a proportion of these lesions displaying mixed tumor plus treatment effect. Median overall survival was 13.4 months (95% CI: 10.5-17.7) from salvage resection.
 
 
 
 Salvage of previously-irradiated BrM remains challenging. This represents the largest known series correlating salvage resection and histopathologically-confirmed viable recurrent BrM with long-term outcomes. Tumor recurrence risk remains high at one year. Further exploration will stratify local progression and radiation necrosis rates by features including extent of resection, degree of viable tumor and adjuvant reirradiation use.
