TLS most often occurs after the initiation of which type of therapy?

• A. Chemotherapy
• B. Radiation therapy
• C. Targeted therapy
• D. Cytotoxic therapy

Answer: (D)

Tumor lysis syndrome happens when a large number of tumor cells are destroyed rapidly, releasing potassium, phosphate, and nucleic acids into the bloodstream, which can lead to hyperkalemia, hyperphosphatemia, hypocalcemia, and hyperuricemia. This rapid cell death is most reliably produced by cytotoxic therapy, which includes traditional chemotherapy agents that kill tumor cells quickly and in large numbers, especially in cancers with high tumor burden. While radiation and some targeted therapies can cause cell death, the pattern and speed of lysis—and thus the risk of TLS—are most closely associated with cytotoxic treatment. So initiating cytotoxic therapy best explains why TLS occurs most often.