Case Report: Rare gastric and bone metastases after early endocrine therapy discontinuation in hormone receptor-positive breast cancer: lessons and therapeutic insights

Breast cancer with gastric metastasis is extremely rare. Non-persistence with adjuvant endocrine therapy is associated with increased recurrence/metastasis risk in hormone receptor-positive (HR+) breast cancer. A 33-year-old female was initially diagnosed with left breast cancer in July 2011, undergoing modified radical mastectomy, adjuvant chemotherapy, radiotherapy, and endocrine therapy (discontinued voluntarily after 1 year). In February 2025, she presented with low back pain and epigastric discomfort; examinations confirmed gastric and multiple bone metastases (ER+,PR+,HER2-). She received first-line endocrine therapy (letrozole+ribociclib+goserelin) combined with denosumab. Re-examination in September 2025 showed normal CEA, significantly decreased CA153, and no disease progression per RECIST 1.1. This case suggests that early endocrine therapy discontinuation may potentially contribute to late recurrence/metastasis. Breast cancer gastric metastasis diagnosis relies on medical history, gastroscopy, and immunohistochemistry (GATA3+, CK7+, CK20-). The combination regimen yielded favorable efficacy, providing clinical reference for similar rare cases.