ERBB2 and neutropenia: Of those who received growth factor support, about half received therapy as primary prophylaxis (20/35 [57.1%] HR + /HER2-low; 10/18 [55.6%] HR-/HER2-low), and half as secondary prophylaxis for neutropenia (15/35 [42.9%] HR + /HER2-low; 8/18 [44.4%] HR-/HER2-low).