[A Case of Bone Metastatic Breast Cancer with Well-Controlled QOL Treated by Mastectomy Followed by S-1 Administration].

We report a case of advanced breast cancer achieving a significant improvement on QOL by mastectomy followed by S-1 administration. The patient was a 50s female brought by an ambulance because of bleeding from huge right breast tumor. CT scan showed bilateral breast cancers with right axially lymph node metastasis. Bilateral total mastectomy with right axially lymph node dissection was performed. Postoperative PET-CT showed multiple bone metastasis. Histopathological findings showed right tumor was scirrhous carcinoma, pT4bpN1cM1, Stage Ⅳ, left tumor was papillotubular carcinoma, pT2NX, Stage ⅡA, both tumor was HR positive, HER2 negative. Postoperative oral tamoxifen therapy was not effective. Second regimen S-1 with denosumab was very effective. The patient is alive with no complaints for 9 years after mastectomy. The purpose of treatments for MBC is to maintain favorable QOL, as well as to improve survival. S-1 could be a valuable agent for breast cancer treatments, since it showed clinical efficacy and mild toxicity, and be given orally.