medwireNews: Patients with hormone receptor-negative (HR–)/human epidermal growth factor receptor 2-positive (HER2+) breast cancer have the highest incidence of brain metastases at diagnosis, followed by those with triple-negative disease, population-based study data show.
These two groups also have the worst survival, report Ayal Aizer (Harvard Medical School, Boston, Massachusetts, USA) and colleagues in JAMA Oncology.
They say their findings “lend support to consideration of screening imaging of the brain for patients with HER2-positive or triple-negative subtypes and extracranial metastases.”
Using the US National Cancer Institute’s Surveillance, Epidemiology, and End Results database, the researchers identified 231,684 adult patients diagnosed with invasive breast cancer between 2010 and 2013. Of these, 968 (0.41%) had brain metastases at diagnosis.
The incidence of brain metastases varied according to breast cancer subtype, ranging from 0.22% in patients with HR+/HER2– disease to 0.61%, 0.68%, and 1.09% in patients with HR+/HER2+, triple-negative, and HR–/HER2+ disease, respectively.
The corresponding rates of brain metastases among the 12,801 patients with metastatic disease to any site at diagnosis were 5.46%, 7.98%, 11.37%, and 11.45%.
Multivariate analysis of the patients with metastatic cancer showed that older age (>40 years), metastatic disease to multiple extracranial sites, and non-HR+/HER2– subtypes were associated with significantly increased likelihoods for brain metastases at diagnosis.
Median survival among the patients with brain metastases was 10 months overall, but ranged from 6 months in patients with triple-negative breast cancer to 21 months in those with HR+/HER2+ disease.
Older age, Black race, being unmarried, having metastatic disease to three extracranial sites (vs 0 or 1), and having a triple-negative subtype (vs HR+/HER2–) were all associated with significantly increased risks for all-cause mortality on multivariate analysis. By contrast, the HR+/HER2+ subtype was associated with reduced mortality.
Aizer and team note that, because guidelines do not currently recommend routine brain imaging in breast cancer, the patients in the study “were likely diagnosed as a result of neurologic symptoms,” and the true incidence of brain metastases was probably underestimated.
The researchers note that when metastases are identified early, they are more amenable to potentially less toxic treatments, such as stereotactic radiosurgery or systemic chemotherapy, than when detected at a later stage.
They conclude: “Whether routine [central nervous system] staging in patients with metastatic breast cancer could reduce the need for neurosurgical resection, whole-brain radiation, or a higher neurologic death rate is not known at this time; our results support the need for further investigation of this very common clinical question.”
By Laura Cowen
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