[Importance of Local Therapy for Oligometastatic Breast Cancer-A Case Report].

A case of successful local treatment for metachronous oligometastases to the lung and mediastinal lymph nodes in a postmenopausal woman with breast cancer is presented. A 44-year-old woman underwent partial mastectomy and left axillary lymph node dissection for right breast cancer. Thirteen years and 3 months after the operation, she was referred to our hospital for a right lung mass detected by mass screening and diagnosed with a metastatic lung tumor from left breast cancer following CT-guided biopsy. She was simultaneously diagnosed with right breast cancer, and pulmonary metastasectomy, right partial mastectomy, and sentinel lymph node biopsy were performed. Two years after the second operation, follow-up CT showed a swollen lymph node at the pre-tracheal space, and endobronchial ultrasound-guided transbronchial needle aspiration confirmed the diagnosis of metastatic breast cancer. The mediastinal lymph node metastasis showed no change in size for 2 years and 7 months with fulvestrant therapy, and no other metastases were found. Proton beam therapy of 60 GyE in 30 fractions was administered to the metastatic lymph node. Substantial tumor shrinkage with no severe toxicity was observed, and to date, the patient has remained disease-free. More cases need to be studied to investigate the appropriate strategy for local therapy in patients with oligometastatic breast cancer.