1092 - Pre-Operative vs. Post-Operative Fractionated Stereotactic Radiotherapy: A Single-Institution Analysis of 534 Resected Metastases

H. K. Perlow¹, S. Hennings², J. Bradshaw², S. Reddy², S. Luu², J. K. Matsui², B. Klamer³, K. Dibs¹, M. R. Harrell¹, J. McGregor⁴, R. R. Lonser⁴, D. Prevedello⁴, J. B. Elder⁵, K. Wu⁴, R. S. Prabhu⁶, S. Zhu¹, R. Singh¹, S. Beyer⁷, J. C. Grecula¹, D. M. Blakaj¹, E. M. Thomas⁷, R. Raval⁷, and J. D. Palmer⁷; ¹Department of Radiation Oncology, The Ohio State University Wexner Medical Center, Columbus, OH, ²The Ohio State University College of Medicine, Columbus, OH, ³The Ohio State University Wexner Medical Center, Center for Biostatistics, Columbus, OH, ⁴Department of Neurosurgery, The Ohio State University Wexner Medical Center, Columbus, OH, ⁵Department of neurosurgery, The James Cancer Center, Ohio State University Wexner Medical Center, Columbus, OH, ⁶Atrium Health Levine Cancer and Southeast Radiation Oncology Group, Charlotte, NC, ⁷Department of Radiation Oncology, The James Cancer Center, Ohio State University Wexner Medical Center, Columbus, OH

Purpose/Objective(s): The standard treatment for patients with large or symptomatic brain metastases and limited intracranial disease is surgical resection followed by post-operative (post-op) stereotactic radiosurgery (SRS). However, SRS can lead to elevated rates of radiation necrosis (RN), meningeal disease (MD), and local failure (LF). Fractionated treatments can deliver a higher biological effective dose and may reduce the risk of LF, and pre-operative (pre-op) treatments may reduce the risk of RN and MD through treating smaller volumes and tumor sterilization. We hypothesize that pre-op fractionated stereotactic radiation therapy (FSRT) will reduce the incidence rate of RN, MD, and LF when compared to patients who receive post-op FSRT. Materials/

Methods: A retrospective analysis was performed at a single institution and included patients who had surgical resection and radiation to at least one brain metastasis. Patients who received pre-op or post-op radiation were eligible for inclusion. Patients with multiple metastases resected, either during the same surgery or at different times in the disease course, were eligible for inclusion. All included patients received FSRT. Outcomes were evaluated on a per-lesion basis. Relevant demographic, clinical, radiation, surgical, and follow up data were collected for each patient. The primary outcome was a composite endpoint defined by 1) LF, 2) MD, and/or 3) Grade 2 or higher (symptomatic) RN.
Results: 458 patients with 534 resected brain metastases were eligible for analysis. The median follow up was 11 months. 235 metastases received pre-op FSRT, and 299 metastases received post-op FSRT. Overall, 15% of patients had multiple brain metastases resected. The most common metastasis locations were frontal (33%), parietal (22%), and cerebellar (19%) with no significant differences between groups. The median planning target volumes were 16 ccs and 36ccs for pre-op and post-op FSRT, respectively (p <0.001). Overall, 6 (2.6%) pre-op and 13 (4.3%) post-op patients experienced LF. 21 (8.9%) pre-op and 38 (12.7%) post-op patients experienced symptomatic RN. 11 (4.7%) pre-op and 29 (9.7%) post-op patients were diagnosed with MD (p=0.031). Overall, 14% of metastases that received pre-op FSRT experienced the composite endpoint, and 24% of metastases receiving post-op FSRT experienced the composite endpoint (p=0.005).
Conclusion: In our study, pre-op FSRT compares favorably to post-op FSRT primarily due to a 50% reduction in the incidence of MD. Differences in symptomatic RN or LF were small on adjusted analyses. Prospective validation of pre-op FSRT is needed.