Introduction
A decade ago, stereotactic radiosurgery (SRS) without whole brain radiotherapy (WBRT) was emerging as preferred treatment for oligometastatic brain metastases (BrM). Studies of cavity SRS after neurosurgery were underway. Data specific to metastatic HER2+ breast cancer (MHBC), describing intracranial, systemic and survival outcomes without WBRT, were lacking. A Phase II study was designed to address this gap.
Method
Adults with MHBC, performance status 0-2, £ five BrM, receiving/ planned for HER2-targeted therapy were eligible. Exclusions included leptomeningeal disease, prior WBRT. Neurosurgery allowed £ 6 weeks before registration and required for BrM > 4 cm. Primary endpoint was 12-month requirement for WBRT. Secondary endpoints; freedom from (FF-) local failure (LF), distant brain failure (DBF), extracranial disease failure (ECDF), overall survival (OS), cause of death, mini-mental state examination (MMSE), adverse events (AE).
Results
Twenty-five patients accrued Decembers 2016 - 2020. The study closed early after slow accrual. Thirty-seven BrM and four cavities received SRS. Four cavities and five BrM were observed. At 12 months: one patient required WBRT (FF-WBRT 95%, 95% CI 72-99), FFLF 91% (95% CI 69-98), FFDBF 57% (95% CI 34-74), FFECDF 64% (95% CI 45-84), OS 96% (95% CI 74-99). Two grade 3 AE occurred. MMSE was abnormal for 3/ 24 patients at baseline and 1 / 17 at 12 months.
Conclusion
At 12 months, SRS and/ or neurosurgery provided good control with low toxicity. WBRT was not required in 95% of cases. This small study supports the practice change from WBRT to local therapies for MHBC BrM.