Oncologic Emergencies: Tumor Lysis Syndrome

The tumor lysis syndrome (TLS), characterized by hyperkalemia, hyperuricemia, hyperphosphatemia and secondary hypocalcemia, is a consequence of treatmentinduced or spontaneous tumor cell death. It usually occurs a few hours to a few days after commencing cytotoxic chemotherapy for tumors with a high percentage of proliferating and drug-sensitive cells. Cell death leads to the release of potassium, phosphate, uric acid, and other purine metabolites into the systemic circulation. When the renal clearance of these chemical moieties is overwhelmed, hyperkalemia, hyperuricemia, hyperphosphatemia and secondary hypocalcemia results. Serum lactate dehydrogenase (LDH) levels are also often elevated concurrently. Uncontrolled TLS progresses to lactic acidosis and acute renal failure, and may end fatally. TLS has been reported in association with a wide variety of tumors. It is most commonly seen in hematologic malignancies with large, bulky adenopathy or high white blood cell counts, especially Burkitt’s lymphoma1-4. A pan-European retrospective chart review identified TLS in 3.4% of patients with acute myeloid leukemia, 5.2% of patients with acute lymphocytic leukemia, and in 6.1% of patients with nonHodgkin’s lymphoma5. TLS occurs relatively rarely in solid tumors, possibly due to their longer doubling time, low growth fraction, and slow response to treatment6. Hyperuricemia is also frequently noted in patients with cancer as an isolated finding. The pan-European retrospective chart review quoted above identified hyperuricemia without TLS in 13.6% of cases, with TLS in an additional 5.3%5. TLS may also occur after ionizing radiation (including total body irradiation in the transplant setting), embolization, radiofrequency ablation, monoclonal antibody therapy, glucocorticoids, interferon and in the setting of hematopoietic stem cell transplantation7. Spontaneously occurring TLS is a result of ongoing cell death in a rapidly growing tumor. Risk factors for the development of TLS are: (1) the presence of bulky adenopathy, hepatosplenomegaly or Table 1: Oncologic emergencies