For example, T-DM1 was active and well tolerated in a population with brain metastases from BC, and metronomic temozolomide in combination with standard dose T-DM1 has shown low-grade toxicity and potential activity in the secondary prevention of HER2+ brain metastases (41, 52), Moreover, thrombocytopenia has been a dose-limiting side effect that can lead to treatment discontinuation (53, 54). The gene discussed is ERBB2; the disease is Thrombocytopenia.