Tumor Lysis Syndrome: Prophylaxis and Treatment
Risk Stratification Determines Management Intensity
All patients undergoing cytotoxic therapy must be stratified into high-risk, intermediate-risk, or low-risk categories before initiating treatment, as this classification dictates whether rasburicase or allopurinol is used for prophylaxis. 1
High-Risk Criteria
- Pre-existing renal impairment (including malignant infiltration), dehydration, or obstructive uropathy 1
- Baseline hyperuricemia >8 mg/dL in children or >10 mg/dL in adults 1
- Bulky disease, high-grade lymphomas (Burkitt, T-cell lymphoblastic NHL), adult ALL, or advanced pediatric ALL 1
- LDH >2× upper limit of normal 1
- High or rapidly rising blast counts 1
- Intensive polychemotherapy regimens (cisplatin, cytarabine, etoposide, methotrexate) 1
Prophylaxis for High-Risk Patients
High-risk patients require rasburicase as first-line prophylaxis, not allopurinol, because rasburicase enzymatically converts existing uric acid to allantoin (5-10 times more soluble), providing immediate reduction of pre-existing hyperuricemia. 1
Rasburicase Regimen
- Dose: 0.20 mg/kg/day IV over 30 minutes for 3-5 days 2, 1
- Timing: First dose must be given ≥4 hours before starting chemotherapy 1
- Efficacy: Achieves 86% reduction in plasma uric acid within 4 hours (vs. 12% with allopurinol; p<0.0001) 1
- In pediatric retrospective data, only 2.6% of rasburicase patients required dialysis versus 16% with allopurinol 1
Mandatory Pre-Treatment Screening
- G6PD deficiency must be excluded before rasburicase administration—failure to screen has resulted in life-threatening hemolysis and methemoglobinemia 1
- Rasburicase is contraindicated in pregnancy, lactation, history of anaphylaxis to rasburicase, or methemoglobinemia 1
Aggressive Hydration Protocol
- Initiate IV hydration ≥48 hours before chemotherapy when feasible 2, 1
- Target urine output ≥100 mL/hour in adults (3 mL/kg/hour in children <10 kg) 2, 1
- Deliver 2-3 L/m²/day of IV fluids 1
- Loop diuretics (not thiazides) may be required to achieve target urine output, except in obstructive uropathy or hypovolemia 2, 1
Hospital Setting Requirement
- High-risk prophylaxis must be delivered in an inpatient facility with immediate dialysis access and nephrology consultation 1
Prophylaxis for Intermediate-Risk Patients
- Aggressive hydration (≥2 L/m²/day) plus either allopurinol 300 mg daily or rasburicase 0.2 mg/kg/day 3
- Agent selection based on baseline uric acid level and renal function 3
Prophylaxis for Low-Risk Patients
- Oral allopurinol 100 mg/m² every 8 hours (maximum 800 mg/day), started 1-2 days before chemotherapy and continued 3-7 days 1
- Combined with vigorous IV hydration ≥2 L/m²/day 1
- Critical dose adjustment: Reduce allopurinol by ≥50% in any degree of renal impairment because both drug and metabolite (oxipurinol) are renally cleared 1
Treatment of Established Tumor Lysis Syndrome
All adults with laboratory or clinical TLS should receive aggressive hydration plus rasburicase, regardless of which specific metabolic abnormalities are present. 3
Rasburicase for Treatment
- Same dosing as prophylaxis: 0.20 mg/kg/day IV over 30 minutes for 3-5 days 2, 1
- Redose only if uric acid remains >4 mg/dL at 12-24 hours after initial dose 1
- Blood samples must be placed immediately on ice to prevent ex vivo enzymatic degradation by rasburicase, which falsely lowers measured uric acid 1
Management of Hyperkalemia
- Mild (<6 mmol/L): Hydration, loop diuretics, sodium polystyrene 1 g/kg orally or by enema 2
- Severe (≥6 mmol/L): Rapid insulin 0.1 units/kg plus 25% dextrose 2 mL/kg, calcium gluconate 50-100 mg/kg IV, and sodium bicarbonate to stabilize cardiac membranes and correct acidosis 2, 3
- Continuous ECG monitoring is mandatory for severe hyperkalemia 2, 3
Management of Hyperphosphatemia
- Mild (<1.62 mmol/L): No treatment required, or aluminum hydroxide 50-100 mg/kg/day divided in 4 doses 2, 3
- Severe or symptomatic: Consider early dialysis 2
Management of Hypocalcemia
- Asymptomatic hypocalcemia should not be treated because calcium administration promotes calcium-phosphate precipitation in tissues and kidneys 2, 1, 3
- Symptomatic only (tetany, seizures, prolonged QT): Single dose calcium gluconate 50-100 mg/kg IV, cautiously repeated if necessary 2, 3
Critical Drug Interactions and Sequencing
Allopurinol and rasburicase must never be given concurrently—simultaneous use leads to xanthine accumulation and risk of xanthine crystal deposition in renal tubules, causing obstructive uropathy. 1, 3
- Correct sequence: Rasburicase first, then transition to oral allopurinol only after completing rasburicase therapy 1
- A phase III trial demonstrated rasburicase followed by allopurinol achieved 78% response rate with time to uric acid control of 4 hours (vs. 27 hours with allopurinol alone) 1
Thiopurine Interaction
- When allopurinol is combined with 6-mercaptopurine or azathioprine, reduce thiopurine dose by 65-75% to avoid toxicity 1
Indications for Renal Replacement Therapy
Early dialysis should be considered when the threshold for RRT may be lower than in other clinical situations, since cell breakdown is ongoing and rapid electrolyte increases cannot be predicted. 4
Specific Indications
- Severe oliguria or anuria despite adequate hydration 2, 3
- Persistent hyperkalemia unresponsive to medical management 2, 3
- Hyperphosphatemia with symptomatic hypocalcemia 2, 3
- Hyperuricemia not responding to rasburicase 3
- Severe volume overload unresponsive to diuretics 3
- Symptomatic uremia (refractory nausea, vomiting, encephalopathy) 3
Dialysis Efficacy
- Hemodialysis reduces plasma uric acid by approximately 50% with each 6-hour treatment 2, 3
- Uric acid clearance is approximately 70-100 mL/min with HD 2
Monitoring Requirements
High-Risk Patients (Prophylaxis)
- Every 12 hours for the first 3 days, then every 24 hours 3
- Measure LDH, uric acid, sodium, potassium, creatinine, BUN, phosphorus, calcium 3
Established TLS (Treatment)
- Every 6 hours for the first 24 hours, then daily until stable 1, 3
- Include vital signs, serum uric acid, electrolytes, and renal function 3
Resuming Chemotherapy After TLS Episode
Nephrology consultation is mandatory for any patient with previous clinical TLS before restarting chemotherapy. 5
Pre-Resumption Requirements
- Uric acid <475 μmol/L (8 mg/dL) 5
- Creatinine <141 μmol/L 5
- pH ≥7.0 5
- All electrolytes (potassium, phosphate, calcium) normalized 5
Prophylaxis for Subsequent Cycles
- All patients with prior TLS must receive rasburicase prophylaxis (0.20 mg/kg/day for 3-5 days) for every subsequent chemotherapy cycle 5
- Initiate aggressive IV hydration 48 hours before chemotherapy, targeting urine output ≥100 mL/hour 5
- Loop diuretics may be required to maintain target urine output 5
Post-Resumption Monitoring
- First 24 hours: Monitor vital signs, uric acid, electrolytes, and renal function every 6 hours 5
- Days 2-3: Continue monitoring every 12 hours 5
- Daily monitoring until stable 5
Common Pitfalls to Avoid
- Using allopurinol in high-risk patients or those with existing hyperuricemia—allopurinol only prevents new uric acid formation and cannot lower existing levels 1
- Failing to reduce allopurinol dose by ≥50% in renal impairment—leads to drug and metabolite accumulation 1
- Correcting asymptomatic hypocalcemia when hyperphosphatemia is present—promotes metastatic calcifications and worsens renal function 2, 1, 3
- Using loop diuretics in anuric or persistently oliguric patients—contraindicated when urine output cannot be achieved despite adequate hydration 3
- Inadequate hydration when resuming chemotherapy after TLS—markedly increases risk of recurrent acute kidney injury 5
- Omitting rasburicase prophylaxis in patients with prior TLS—substantially raises likelihood of recurrent TLS 5
- Not placing blood samples on ice after rasburicase—continued ex vivo enzymatic degradation falsely lowers measured uric acid 1
Interventions NOT Recommended
- Urine alkalinization is not recommended, especially with rasburicase, because it increases risk of calcium-phosphate precipitation 1, 3
- Thiazide diuretics have no role in TLS management and are ineffective when renal function is impaired 3
- Additional prednisone beyond chemotherapy regimen provides no benefit for acute TLS management 3