Timing of Adjuvant Fractionated Stereotactic Radiosurgery Impacts Local Control of Resected Brain Metastases.

OBJECTIVE: For resected brain metastases (BM), stereotactic radiosurgery (SRS) is often offered to minimize local recurrence (LR). Although the aim is to deliver SRS within a few weeks of surgery, a variety of socioeconomic, medical, and procedural issues can cause delays. We evaluated the relationship between timing of postoperative SRS and LR.

METHODS: We retrospectively identified a consecutive series of BM patients managed with resection and SRS or fractionated SRS at our institution from 2012-2018. We assessed the correlation between time to SRS, and other demographic, disease, and treatment variables, and LR, local recurrence-free survival (LRFS), distant recurrence (DR), distant recurrence-free survival, and overall survival (OS).

RESULTS: 133 patients met inclusion criteria. Median age was 64.5 years. Approximately half of patients had a single BM, and median BM size was 2.9 cm. Gross total resection (GTR) was achieved in 111 (83.5%) patients, and >90% received fractionated SRS. Median time to SRS was 37.0 days and LR rate was 16.4%. Time to SRS was predictive of LR. Median time from surgery to SRS was 34.0 days for patients without LR, vs. 61.0 days for those with LR (p<0.01). LR was 2.3% with SRS administered ≤4 weeks postoperatively, compared to 23.6% if >4 weeks (p<0.01). LRFS was also improved for patients who had SRS at ≤4 weeks (p=0.02). Delayed SRS was also predictive of DR (p=0.02), but not OS.

CONCLUSIONS: In this retrospective study, the strongest predictor of LR following postoperative SRS for BM was time to SRS, and a cut-off of 4 weeks was a reliable predictor of recurrence. These findings merit investigation in a prospective, randomized trial.