Supplementary Material for: A case of tumor lysis syndrome during palliative radiotherapy for breast cancer metastases

Tumor lysis syndrome (TLS) is the rapid disintegration of a malignant tumor treated with anticancer drugs or radiation, causing electrolyte abnormalities such as elevated uric acid levels, elevated potassium and phosphorus levels, and decreased calcium levels. These abnormalities can lead to hypotension, renal dysfunction, consciousness disorders, and even death in some cases. The current patient was a 65-year-old woman who had breast cancer with local invasion, lung metastasis, and bone metastasis from the time of the initial disease onset. Despite the administration of various chemotherapy and hormone therapy regimens, the tumor increased gradually, and at 2 years and 5 months after the initial onset, pain and bleeding from metastatic infiltration of the cervical lymph nodes were noted. Therefore, radiotherapy was indicated for palliation of pain and bleeding caused by metastatic invasion of the cervical lymph nodes. Irradiation (30 Gy/10 fr) was performed with a 3-field technique using 4MVX and 10MVX. Approximately 11 h after the initial irradiation, symptoms such as respiratory distress, tachycardia, and hypotension were observed. Blood tests revealed hyperuricemia and hyperkalemia, leading to a diagnosis of TLS. Dialysis and electrolyte correction were immediately initiated resulting in normalization of electrolytes and stabilization of the blood pressure. It is crucial to understand that TLS is relatively rare but can occur after radiation therapy or in solid tumors, and warrants a prompt response if suspected based on symptoms or blood findings.