Dear Editor,

I want to congratulate Cagney and their colleagues [1] in which they investigated intracranial recurrence patterns of brain metastases from breast cancer after brain-directed radiation to facilitate subtype-specific management paradigms. They reported a strong association between breast cancer subtype and intracranial recurrence patterns after brain-directed radiation, particularly local progression for HER2+ and distant progression for TNBC patients. However, the authors did not consider ER(+)/HER2(+) and ER-/HER2(+) as a different subtype. Analysis of HER2+ metastatic breast cancer has often been performed disregarding the ER status of the disease. Recent study examined the metastatic pattern and prognosis of both ER+/HER2+ and ER−/HER2+ 86,093 breast cancer patients [2]. This large study showed that patients with ER+/HER2+ and ER−/HER2+ breast cancers had different metastatic patterns and patients with ER−/HER2+ breast cancer had worse prognosis. Taken all together, ER(+)/HER2(+) and ER−/HER2(+) breast cancers might have different intracranial recurrence patterns after brain-directed radiation for brain metastases. This issue merits further investigation.