RADT-01. PRE-OPERATIVE SINGLE FRACTION VERSUS FRACTIONATED STEREOTACTIC RADIOTHERAPY: A SINGLE-INSTITUTION ANALYSIS OF 299 RESECTED METASTASES

Abstract The treatment standard for patients with large or symptomatic brain metastases and limited intracranial disease is surgical resection followed by post-operative (post-op) stereotactic radiosurgery (SRS). The multicenter PROPS-BM cohort showed how pre-operative (pre-op) SRS may lead to a reduced incidence of radiation necrosis (RN), local failure (LF), and meningeal disease (MD) compared to historical controls. Fractionated treatments can deliver a higher biological effective dose and may reduce the incidence of LF and MD. 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 pre-op SRS. Patients who had surgical resection and pre-operative radiation to at least one brain metastasis at a single institution were retrospectively analyzed. Outcomes were evaluated on a per-lesion basis. The primary outcome was a composite endpoint defined by 1) LF, 2) MD, and/or 3) Grade 2 or higher (symptomatic) RN. 260 patients with 299 resected brain metastases were eligible for analysis. 64 metastases received SRS and 235 metastases received FSRT. 38 patients had multiple metastases resected pre-operatively. The median gross tumor volume was 4 ccs for SRS and 10 ccs for FSRT (p<0.001). Overall, 4 (6.3%) SRS and 6 (2.6%) FSRT patients experienced LF. 4 (6%) SRS and 21 (8.9%) FSRT patients experienced Grade 2 or higher RN. 3 (4.7%) SRS and 11 (4.7%) FSRT patients were diagnosed with MD. 14% of both SRS and FSRT patients experienced the composite endpoint. There were no statistically significant differences in outcome between these two treatment groups. In our study, pre-op SRS and FSRT both appear to be safe and effective options to treat resectable brain metastases. It is important to prospectively compare pre-op SRS and FSRT in matched cohorts to assess any differences in treatment efficacy and toxicity.