USMLE Prep - Medical Reference Library

Tumor Lysis Syndrome — Prevention, Rasburicase vs Allopurinol, and Renal Protection

System: Hematology Oncology • Reviewed: Sep 2, 2025 • Step 1Step 2Step 3

Synopsis:

High‑grade hematologic malignancies carry TLS risk at chemo initiation. Stratify risk; give aggressive hydration, allopurinol for low‑moderate risk, or rasburicase for high‑risk or established hyperuricemia. Monitor electrolytes closely; treat hyperkalemia/hyperphosphatemia; consider early dialysis for AKI.

Key Points

  • Use the highest‑yield diagnostic test early; do not let testing delay time‑critical therapy.
  • Set objective targets and reassess frequently.
  • Plan definitive source control or disease‑specific therapy when indicated; document follow‑up and patient education.

Algorithm

  1. Assess TLS risk; start hydration; choose allopurinol vs rasburicase appropriately.
  2. Monitor labs frequently and treat electrolyte derangements per protocol.
  3. Escalate to dialysis for refractory complications; plan secondary prevention for future cycles.

Clinical Synopsis & Reasoning

High‑grade hematologic malignancies carry TLS risk at chemo initiation. Stratify risk; give aggressive hydration, allopurinol for low‑moderate risk, or rasburicase for high‑risk or established hyperuricemia. Monitor electrolytes closely; treat hyperkalemia/hyperphosphatemia; consider early dialysis for AKI.


Treatment Strategy & Disposition

Stabilize ABCs. Initiate guideline‑concordant first‑line therapy with precise dosing and continuous monitoring. Escalate to advanced/procedural interventions based on explicit failure criteria. Define ICU, step‑down, and ward disposition triggers; involve specialty teams early.


Epidemiology / Risk Factors

  • Risk varies by comorbidity and precipitants; see citations for condition‑specific data.

Investigations

TestRole / RationaleTypical FindingsNotes
Risk stratification (disease burden, LDH, baseline uric acid)PreventionIdentify high‑risk patientsPlan prophylaxis
Serial electrolytes/uric acid and urine outputMonitoringDetect TLS earlyTelemetry
Baseline renal ultrasound (selected)AdjunctObstruction or stones

High-Risk & Disposition Triggers

TriggerWhy it mattersAction
Bulky/high-grade lymphoma or ALL starting chemoTLS riskProphylaxis (hydration + rasburicase/allopurinol); ICU if severe
Rising K+, phosphorus; falling Ca2+Arrhythmia/seizure riskAggressive correction; telemetry
AKI/oliguriaRenal failureDialysis consult early
Uric acid >8–10 mg/dL despite prophylaxisFailureRasburicase; escalate
Sepsis or tumor burden progressionComplex courseOnc + ICU co-management

Pharmacology

Medication/InterventionMechanismOnsetRole in TherapyLimitations
Aggressive IV hydration (2–3 L/m²/day)Renal protectionHours‑daysMaintain urine outputAvoid overload
Allopurinol 300 mg/day (or 100 mg TID) for preventionXanthine oxidase inhibitionDaysLow/mod risk prophylaxisAdjust in CKD
Rasburicase 0.1–0.2 mg/kg IV (or fixed dose)UricaseHoursRapidly lowers uric acidG6PD deficiency contraindication
Electrolyte management protocols; dialysis for refractory hyperkalemia/AKISupportiveHoursPrevent complications

Prognosis / Complications

  • Outcome depends on timeliness of diagnosis and definitive therapy; monitor for complications.

Patient Education / Counseling

  • Provide red‑flag education, adherence guidance, and explicit return precautions; arrange timely specialty follow‑up.

References

  1. ASCO/ASH TLS guidance — Link