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For brain metastases (BM) requiring surgery, pre-operative stereotactic radiosurgery (SRS) may have advantages compared to post-operative cavity SRS. The aim of this study was to prospectively assess outcomes for a cohort of patients receiving pre-operative SRS for BM treated at a single centre.

Participants required a confirmed diagnosis of metastatic cancer prior to enrolment and had at least one BM for resection. Pre-operative SRS treatment was agreed to in a multidisciplinary forum and intended to be given no more than 2 days prior to surgery. SRS was delivered in a single fraction on the Leksell Gamma Knife ICON platform, with dose adjusted according to BM volume (≤8.2cc received 18-20Gy, 8.2-14.1cc received 16-18Gy, ≥14.1-22.5cc received 14-16Gy and ≥22.5cc received 14Gy). Post-operative T1-weighted gadolinium-enhanced MRI was performed within 48 hours of surgery to assess extent of resection, followed by standard clinical and radiological MRI surveillance imaging every 2-3 months.

21 participants (a total of 22 BM treated on protocol) were recruited between January 2020 and August 2022. The most common primary histologies were non-small cell lung cancer (36%), melanoma (36%) and breast cancer (9%). The median BM volume prior to surgery was 6.8 cc (range 3-40); 10 BM were ≥10 cc volume and 5 BM were >20 cc. All participants received protocol treatment as planned. The median interval between pre-operative SRS and surgery was 1 day (range 0-15). Post-operative MRI confirmed gross total resection in all cases. The median duration of inpatient stay after surgery was 3 days (range 1-40). 15 patients restarted and/or commenced systemic therapy, with a median interval of 22 days from SRS (range 6-99). One local recurrence occurred, and was within 3 months of initial surgery.  No cases of leptomeningeal recurrence, wound complications or radionecrosis were observed. The most common acute toxicities experienced within 3 months of SRS were headaches (9%) and fatigue (14%). Overall survival from date of pre-operative SRS was 67% at 1 year (95% CI: 48–93%) and median follow up was 14.7 months (range 2-29).

SRS delivered before surgery for BM confers a high rate of local control and no apparent increase in the risk of acute wound complications. Compared to post-operative cavity SRS, pre-operative SRS may also help reduce the risk of leptomeningeal disease and radionecrosis, whilst facilitating prompt initiation of systemic therapy after surgery.