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RADT-12. PRE- AND POST-OPERATIVE RADIATION TREATMENT PLANNING FOR PATIENTS RECEIVING STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES: A VOLUMETRIC ANALYSIS

2022; Oxford University Press; Volume: 24; Issue: Supplement_7 Linguagem: Inglês

10.1093/neuonc/noac209.202

1523-5866

Cindy Ho, Haley K. Perlow, Alex R. Ritter, Yevgeniya Gokun, Jennifer K. Matsui, Joshua Wang, Mark Damante, Dukagjin M. Blakaj, Sasha Beyer, Evan Thomas, Russell R. Lonser, Douglas A. Hardesty, Raju R. Raval, Joshua D. Palmer, J Brad Elder,

Advanced Radiotherapy Techniques

Abstract BACKGROUND Pre-operative stereotactic radiosurgery (SRS) has emerged as a recent treatment option to treat large or symptomatic brain metastases. Compared to post-operative SRS, pre-operative treatment may reduce rates of radiation necrosis (RN) and meningeal disease through treating a smaller treatment volume and by preventing post-operative tumor seeding. We hypothesize that pre-operative radiation volumes will be smaller than post-operative volumes, which in turn may lead to a decreased treatment morbidity. METHODS A retrospective analysis was conducted and patients who had surgical resection and post-operative SRS or fractionated stereotactic radiosurgery (FSRT) for a posterior fossa brain metastasis were eligible for inclusion. Both pre-operative and post-operative MRIs were required to allow for accurate radiation target delineation. A pre-operative tumor volume was added for each patient, and the post-operative clinical treatment volume (CTV) used for radiation treatment was included. Pre-operative tumor and post-operative cavity volumes were compared using Wilcoxon signed rank test. RESULTS 28 patients who received post-operative SRS or FSRT from 1/1/2016-12/31/2020 were included in this analysis. The mean pre-operative tumor volume was 14.9 ccs, and the mean post-operative CTV was 21.0 ccs (p < 0.01). 75% of patients had a smaller initial tumor size compared to the post-operative CTV used for radiation treatment planning. For patients with at least 4 follow up MRIs (n = 8), the size of the post-operative cavity progressively decreased with a mean initial cavity volume of 18.9 ccs and mean follow up volumes of 8.1, 7.1, 6.9, and 6.2 ccs. CONCLUSIONS In this study evaluating patients who received post-operative SRS, the pre-operative tumor volume was lower than the post-operative CTV for most patients. Previous studies including PROPS-BM have shown how pre-operative treatment may reduce the risk of RN because smaller radiation volumes are used. Pre-operative radiosurgery for patients with brain metastases requires prospective validation.