[Molecular Targeted Therapies Effective for Brain Metastases and Their Position in Guidelines].

Various driver gene mutations have been identified, and agents targeting these molecular abnormalities have been developed and are being used in treatment. Some of these driver gene abnormalities are also associated with a high frequency of brain metastases. In patients with non-small cell lung cancer (NSCLC), more than 80% of brain metastases had a molecular target. Tyrosine kinase inhibitors are highly effective against brain metastases in patients with epidermal growth factor receptor-mutated or anaplastic lymphoma kinase fusion-positive NSCLC. Recently, the efficacy of the antibody-drug conjugate, T-DXd, against HER2+ breast cancer has also been confirmed. Many other molecularly targeted therapies are also effective against brain metastases; thus, many patients with brain metastases may benefit from these treatments. Although molecularly targeted therapy has become an important treatment modality for brain metastases, its limitations, such as not being curative and having a limited duration of effect, are also becoming clear. In the era of precision medicine, it is important to coordinate conventional local treatment with individually tailored molecularly targeted therapy. For that purpose, it is essential to understand the efficacy and limitations of targeted therapy for brain metastasis for each molecular target.