Clinical Effects of Hypomethylating Agents in Patients with Newly Diagnosed Myelodysplastic Syndrome Who Received DNA-Damaging Chemotherapy for Metastatic Breast Cancer

The cumulative risk of therapy-related myelodysplastic syndrome (t-MDS) in breast cancer patients exposed to chemotherapy and/or radiotherapy is significantly high compared to that in other cancer patients. This report reviews the use of hypomethylating agents (HMAs) to treat a 57-year-old woman newly diagnosed with MDS during palliative chemotherapy for metastatic breast cancer. Over a period of 6 years, the patient received several DNA-damaging chemotherapeutics including doxorubicin, cyclophosphamide, and paclitaxel. Repeated thrombocytopenia was the main reason for suspecting secondary hematologic malignancy. She was diagnosed with t-MDS based on bone marrow examination and her treatment history for breast cancer. While azacitidine was originally administered to stabilize MDS, it also stabilized the patient's lung and lymph node metastases without any major toxicity. Therefore, the current case highlights the promising effects of HMAs for treating t-MDS following heavily pretreated breast cancer.