De Novo Stage IV Breast Cancer with Durable Response Lasting for 17 Years to Endocrine Therapy Alone—A Case Report—

Abstract

A 69-year-old woman who noticed a lump in her left breast 7 years before her first visit had left it untreated. She was referred to our hospital because of breast ulceration, bleeding, and foul odor. She was diagnosed with hormone receptor-positive (HR+), HER2-negative (HER2-), cT4bN1M1 (lung and liver) Stage IV left breast cancer. She received an aromatase inhibitor as the primary therapy. She responded well ; however, a computed tomography scan performed 6 years and 7 months after the therapy revealed an increase in the size of the mammary tumor, and treatment was switched to fulvestrant. The tumor has continued to reduce in size until now, 10 years and 10 months after the therapy. The combination of endocrine therapy and CDK4/6 inhibitor is currently recommended as the primary therapy for HR+ HER2- metastatic breast cancer. However, we report a case of de novo Stage IV breast cancer in which a durable response that lasted for 17 years was achieved using endocrine therapy alone.