Impact of systemic therapy after stereotactic radiosurgery in patients with limited brain-only metastasis.
BACKGROUND: The impact of systemic therapy (ST) on outcomes for patients with brain-only metastases (BrM) in the absence of extracranial disease (ECD) is not well established. We compared outcomes between patients with BrM treated with stereotactic radiosurgery (SRS) who received ST ≤3 months (mos), >3 mos, or not at all after SRS. METHODS: We identified BrM patients who completed SRS across two institutions from 1/2015 to 12/2020. Intracranial progression after SRS was determined by brain MRI radiographic recurrence. Overall survival (OS) and intracranial progression free survival (iPFS) estimates were also generated. RESULTS: In total, 342 patients with BrM were identified. Primary sites included lung (73%), breast (12%), and additional sites (15%). Almost half, 169 (49%), received no ST, 80 (23%) received ST ≤3 mos, and 93 (27%) received ST >3 mos after SRS. Median age was younger in the ST >3 mos cohort (60.5years) compared with ST <3mo (67.7years) and no ST (67.0years), P = .0002. Median OS differed significantly between groups: ST ≤3 mos with 24.9mos (95%CI: 16.6-51.1), ST >3 mos with 27.5mos (95% CI: 20.6-37.5), and no ST with 11.0mos (95%CI: 9-17.5), P = .002. Median iPFS differed significantly between groups: ST ≤3 mos 16.1mos (95% CI: 9.5-33.7), ST >3 mos 8.9mos (95% CI: 6.9-13.5), and no ST 10.0mos (95% CI: 6.7- 15.1). However, timing of ST was not significant multivariate analysis. CONCLUSIONS: In our cohort of BrM patients, ST after SRS improves OS regardless of timing. ST ≤3 mos may improve iPFS compared with ST >3 mos after SRS, which warrants further investigation. Appropriate patients with BrM should be referred for a multi-disciplinary discussion of ST following SRS.
