Also, brain metastases are associated with a worse prognosis in HER2-altered NSCLC and are present at the onset of advanced disease in 19–30% of cases, and develop during the treatment up to 47% of cases due to the lack of brain activity in classical treatments (chemotherapy and immunotherapy) that do not cross the blood–brain barrier [23,24]. The gene discussed is ERBB2; the disease is non-small cell lung carcinoma.