Breast cancer brain metastases localization and risk of hydrocephalus: a single institution experience

Purpose Brain metastases occur in up to one-third of patients with breast cancer. aromatase, a marker for estrogen activity that has been shown to promote such metastasis, heavily concentrates in certain midline structures of brain. We hypothesize that breast cancer metastasizes more often to brain areas with higher aromatase activity and that these patients have a higher risk of developing obstructive hydrocephalus. Methods In our retrospective review of 709 patients who underwent stereotactic radiosurgery (January 2014–May 2020), we identified 358 patients treated for metastatic breast or lung cancer. The MRI scan that first showed evidence of brain metastases was reviewed and number of metastases counted by location. Procedures used to treat obstructive hydrocephalus were recorded. Chi square test was used for statistical analysis. Results Of 358 patients, 99 patients with breast cancer had 618 brain metastases and 259 patients with lung cancer had 1487 brain metastases. Compared with expected distribution of brain metastases based on regional brain volumes and metastatic lung carcinoma as a control, patients with breast cancer more often had metastases to the cerebellum, diencephalon, medulla, and parietal lobe, and underwent significantly more neurosurgical interventions for treatment of obstructive hydrocephalus. Conclusion Brain metastases in patients with breast cancer occurred more often along midline structures of the brain, which we believe may be associated with the increased estrogen activity in these structures. This finding is important for physicians who treat patients with metastatic breast cancer given the higher possibility of developing obstructive hydrocephalus.