Intracranial outcomes following neurosurgical resection in patients with brain metastases secondary to HER2-positive breast cancer versus other subtypes.

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Neurosurgical resection serves an important role in select patients with breast cancer and brain metastases but can delay systemic therapy and yield complications. Consequently, identification of patients most likely to benefit from surgery is important. Given the poorer long-term intracranial responses to radiotherapy sometimes observed in HER2-positive (HER2 +) patients, we investigated whether neurosurgical resection is differentially beneficial in this population. We identified 633 patients with newly diagnosed brain metastases arising from breast cancer managed at Brigham and Women's Hospital/Dana-Farber Cancer Institute between 2010 and 2022. Patients were stratified by breast cancer subtype: HER2 + (N = 189), hormone receptor positive (HR +)/HER2- (N = 267), and triple negative (N = 177). Per-patient and per-metastasis outcomes were evaluated; interaction models assessing the impact of neurosurgical resection by subtype were constructed. Relative to HR + /HER2- subtype, omission of upfront neurosurgical resection in patients with HER2 + disease was associated with increased subsequent utilization of salvage stereotactic radiation, whole brain radiotherapy, and craniotomy (interaction HR 2.02 [95% CI, 1.04-3.93], p = 0.04; HR 3.92 [95% CI, 1.24-12.40], p = 0.02; HR 4.98 [95% CI, 1.34-18.58], p = 0.02, respectively). Tumors stemming from HER2 + versus HR + /HER2- primaries displayed increased local recurrence when upfront neurosurgical resection was omitted (interaction HR 3.62 [95% CI, 1.06-12.38], p = 0.04). No such associations were noted when comparing triple negative to HR + /HER2- subtype (p-interaction > 0.05 in all cases). Patients with HER2 + disease and brain metastases may disproportionately benefit from upfront neurosurgical resection relative to other subtypes. If validated, our results may suggest a lower threshold to consider surgery in brain metastases secondary to HER2 + breast cancer.