Introduction: Post-operative (Post) stereotactic radiosurgery (SRS) after resection of brain metastases (BM) is an increasingly accepted regimen. However, pre-operative (Pre) SRS has also been shown to be a viable approach. The goal of this multi-institutional retrospective study was to compare the patterns of failure and toxicities of these two SRS paradigms.
Methods: The records of patients who underwent resection of BM and either pre-SRS or post-SRS alone between 2005-2013 at 2 institutions were reviewed. Pre-SRS used a dose reduction strategy based on tumor size, followed by planned resection within 48 hours. Cumulative incidence with competing risk of death was used to determine estimated rates.
Results: 180 consecutive patients underwent resection of 189 BM, with 66 (36.7%) receiving pre-SRS and 114 (63.3%) receiving post-SRS. Median PTV margin (0 vs. 1 mm) and peripheral dose (14.5 vs. 18Gy) differed between cohorts (pre vs. post-SRS). However, median GTV volume (8.3 vs. 9.2cc, p=0.85) and proportion with GTV volume >14cc (33.3% vs. 24.2%, p=0.24) were similar. The median imaging follow-up period was 24.6 months for alive patients. The 2-year rates (pre-SRS vs. post-SRS) of cavity local recurrence (LR), distant brain recurrence (DBR), leptomeningeal disease (LMD), radiation necrosis (RN), and symptomatic RN were: 22.8% vs. 15.4% (p=0.33), 48% vs. 44.6% (p=0.84), 3.2% vs. 16.6% (p=0.01), 8.2% vs. 28.5% (p=0.001), and 4.9% vs. 16.4% (p=0.01). Salvage whole brain radiation (WBRT) use did not differ (21.2% vs. 13.2%, p=0.23). The composite endpoint of LR, LMD, or RN occurrence favored the pre-SRS cohort (30.3% vs. 53.5%, p=0.004).
Conclusions: Pre-SRS and post-SRS for resected BM provide similarly favorable rates of cavity local control and risk of DBR, but with significantly higher rates of RN, symptomatic RN, and LMD occurrence in the post-SRS cohort. Despite higher LMD, salvage WBRT rates were similar, most likely due to differences in salvage strategy between institutions. A prospective clinical trial is warranted to compare these treatment approaches.
Patient Care: The strategy of dose reduced pre-operative radiosurgery for resected brain metastases may be associated with reduced toxicity in the form of radiation necrosis and reduced risk of leptomeningeal disease recurrence versus post-operative SRS. With the goal of effective palliation, pre-operative SRS may represent an improved treatment strategy for these patients.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) describe the pre-operative and post-operative SRS paradigms for resected brain metastases, 2) Understand the rates and similarities in local cavity control between strategies, and 3) discuss the differences in toxicity (primarily radiation necrosis) and patterns of recurrence (primarily leptomeningeal disease) between strategies.