Brain metastases (BM) are common in patients with HER2-positive and triple-negative breast cancer. In this study we aim to report clinical outcomes with LINAC-based stereotactic radiosurgery/radiotherapy (SRS/SRT) for BM in patients of breast cancer.

Clinical and dosimetric records of breast cancer patients treated for BM at our institute between May, 2015 and December, 2019 were retrospectively reviewed. Patients of previously treated or newly diagnosed breast cancer with at least a radiological diagnosis of BM; 1–4 in number, ≤3·5 cm in maximum dimension, with a Karnofsky Performance Score of ≥60 were taken up for treatment with SRS. SRT was generally considered if a tumour was >3·5 cm in diameter, near a critical or eloquent structure, or if the proximity of moderately sized tumours would lead to dose bridging in a single-fraction SRS plan. The median prescribed SRS dose was 15 Gy (range 7–24 Gy) and SRT dose was 27 Gy in 3 fractions.

Clinical assessment and MR imaging was done at 6 weeks post-SRS and then every 3 months thereafter. Intracranial progression-free survival (PFS) and overall survival (OS) were calculated using Kaplan–Meier method and subgroups were compared using log rank test.

Total, 40 tumours were treated in 31 patients. The median tumour diameter was 2·3 cm (range 1·0–4·6 cm). SRS and SRT were delivered in 27 and 4 patients, respectively. SRS/SRT was given as a boost to whole brain radiotherapy (WBRT) in four patients and as salvage for progression after WBRT in six patients. In general, nine patients underwent prior surgery. The median follow-up was 7·9 months (0·2–34 months). Twenty (64·5%) patients developed local recurrence, 10 (32·3%) patients developed distant intracranial relapse and 7 patients had both local and distant intracranial relapse. The estimated local control at 6 months and 1 year was 48 and 35%, respectively. Median intracranial progression free survival (PFS) was 3·73 months (range 0·2–25 months). Median intracranial PFS was 3·02 months in patients who received SRS alone or as boost after WBRT, while it was 4·27 months in those who received SRS as salvage after WBRT (p = 0·793). No difference in intracranial PFS was observed with or without prior surgery (p = 0·410). Median overall survival (OS) was 21·7 months (range 0·2–34 months) for the entire cohort. Patients who received prior WBRT had a poor OS (13·31 months) as compared to SRS alone (21·4 months; p = 0·699).

In patients with BM after breast cancer SRS alone, WBRT + SRS and surgery + SRS had comparable PFS and OS.