[A Case of Multiple Lung Metastases from Breast Cancer Successfully Treated with Endocrine Therapy].

A 40-year-old woman underwent right partial mastectomy and axillary lymph node dissection. Pathological examination confirmed right breast cancer(T2N0M0, Stage ⅡA, mucinous, ly3, v0, weakly positive ER and PgR). After surgery, she received radiotherapy for residual mammary gland cancer and endocrine therapy as adjuvant treatment for 5 years. Seven years after the first surgery, computed tomography showed multiple lung tumors. Transbronchial lung biopsy revealed lung metastasis from breast cancer(strongly positive ER and PgR, negative HER2). She received first-line endocrine therapy, and the response was classified as stable disease(SD). Three years later, the disease control became poor. Second-line endocrine therapy was then administered, and the response was classified as partial response(PR)for 3 years. After that, we modified the regimen to monotherapy of letrozole, and she achieved PR for a further 3 years. In the treatment for patients with metastatic hormone receptor-positive breast cancer, it is important to consider the sensitivity of endocrine therapy, such as relapse-free survival or the expression of hormone receptors in metastatic tumors.