USMLE Prep - Medical Reference Library

Tumor Lysis Syndrome — Risk Stratification, Rasburicase/Allopurinol, and Renal Support

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

Synopsis:

Rapid tumor cell breakdown after cytotoxic therapy (or spontaneously) causing hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia. Risk‑stratify, start aggressive hydration, give allopurinol for prevention or rasburicase for treatment, and monitor electrolytes/renal function closely; initiate dialysis when refractory.

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 ± allopurinol before chemotherapy.
  2. If TLS develops or high-risk labs → rasburicase; aggressive electrolyte management.
  3. Consider RRT for refractory hyperkalemia, acidosis, or volume overload; continue intensive monitoring.

Clinical Synopsis & Reasoning

Rapid tumor cell breakdown after cytotoxic therapy (or spontaneously) causing hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia. Risk‑stratify, start aggressive hydration, give allopurinol for prevention or rasburicase for treatment, and monitor electrolytes/renal function closely; initiate dialysis when refractory.


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
Cairo‑Bishop criteria labs q4–6 hDiagnosis/severityElectrolyte derangements and creatinine riseTrend closely
ECG and telemetrySafetyArrhythmia risk with K+/Ca2+ changes
Urine output monitoring and ultrasound (selected)ComplicationsObstruction/AKIGuide RRT

High-Risk & Disposition Triggers

TriggerWhy it mattersAction
High-risk regimens or bulky, chemosensitive tumorsImpending TLSProphylaxis with hydration + allopurinol/rasburicase; ICU if severe
Uric acid >8 mg/dL, K+ >6, Phos >6 with rising CrRenal failure/arrhythmia riskRasburicase; dialysis if refractory
Oliguria/volume overloadWorsening clearanceDiuretics; consider CRRT
Severe hypocalcemia with tetany/arrhythmiaLife-threateningTreat cautiously; correct phosphate first
G6PD deficiency (rasburicase)Hemolysis riskCheck status; avoid if deficient

Pharmacology

Medication/InterventionMechanismOnsetRole in TherapyLimitations
Aggressive IV hydration 2–3 L/m²/dayPrevention/treatmentHoursEnhance excretionAvoid K+/Ca2+ fluids
Allopurinol 300 mg/day (or weight‑based pediatrics) for prophylaxisXO inhibitorDaysPrevents uric acid formationStart before chemo
Rasburicase 0.1–0.2 mg/kg IV (treatment)Uricolytic enzymeHoursRapidly lowers uric acidScreen for G6PD deficiency
Manage K+/Phos/Ca with standard protocolsElectrolyte controlHoursPrevent arrhythmia/AKIDialysis if refractory

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