How is tumor lysis syndrome treated in pediatric acute lymphoblastic leukemia (ALL)?

Updated: Jan 03, 2019
  • Author: Vikramjit S Kanwar, MBBS, MBA, MRCP(UK), FAAP; Chief Editor: Jennifer Reikes Willert, MD  more...
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Answer

Before and during the initial induction phase of chemotherapy, patients may develop tumor lysis syndrome, which refers to the metabolic derangements caused by the systemic and rapid release of intracellular contents as chemotherapy destroys leukemic blasts. Because some cells can die before therapy, such metabolic changes can occur even before therapy begins.

Primary features of tumor lysis syndrome include hyperuricemia (due to metabolism of purines), hyperphosphatemia, hypocalcemia, and hyperkalemia. Hyperuricemia can lead to crystal formation with tubular obstruction and acute renal failure requiring dialysis. Therefore, electrolyte and uric acid levels should be closely monitored throughout initial therapy.

To prevent complications of tumor lysis syndrome, patients should initially receive intravenous (IV) fluids at approximately twice the maintenance rates without potassium; this rate may vary depending on the condition of the patient.

Sodium bicarbonate may be added to the IV fluid to achieve moderate alkalinization of the urine (pH level, 7.5-8) to enhance the excretion of uric acid. A urine pH level higher than this should be avoided to prevent crystallization of hypoxanthine or calcium phosphate.

The standard prophylactic treatment for malignancy-associated hyperuricemia includes allopurinol. By blocking the enzyme xanthine oxidase, allopurinol blocks uric acid formation. Patients at high risk for tumor lysis still need to excrete pre-existing uric acid, which is unaffected by the use of allopurinol. Rasburicase, a recombinant urate oxidase, has the ability to catalyze the enzymatic oxidation of uric acid to a much more urine soluble product, allantoin, and is invaluable is situations with high uric acid build up (eg, ALL with hyperleukocytosis). Due to its expense, rasburicase is not routinely recommended for every ALL patient.

By definition, hyperleukocytosis refers to WBC counts in excess of 100,000/mcL (100 x 109/L), but patients with ALL (unlike patients with AML) are unlikely to suffer severe complications until WBC counts exceed 300,000/mcL (300 x 109/L). St Jude Children’s Research Hospital was unable to demonstrate a clear benefit from leukophoresis for newly diagnosed patients with ALL with WBC counts exceeding 200,000/mcL (200 x 109/L), and it is therefore no longer routinely recommended.


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