7. Tumor Lysis Syndrome

Quick Recap

Renal System, Protocol 7/7 — completing the Renal System.

1. Definition & Pathophysiology

TLS = clinical syndrome from SUDDEN release of potassium, phosphate, and uric acid (from purine metabolism) by malignant cells undergoing rapid cell death — spontaneous or, more commonly, chemotherapy/radiation/corticosteroid-induced.

Cascade: hyperkalemia is usually the EARLIEST and most severe manifestation. Phosphate release binds calcium -> calcium-phosphate precipitation in renal tubules ALONGSIDE uric acid crystals -> kidney injury/failure AND clinically significant hypocalcemia. Renal dysfunction then REDUCES phosphate/uric acid clearance, worsening the metabolic derangements in a self-perpetuating cycle — the AKI is both a consequence of TLS and an amplifier of it.

Highest incidence: hyperleukocytosis (acute leukemias), high tumor burden, or rapid chemotherapy response (CLL, small cell lung cancer). Hematologic malignancies have the highest rate (up to ~40% in some series) and can occur SPONTANEOUSLY (i.e., before any treatment is given, from the tumor's own high turnover). Pre-existing renal insufficiency is an independent risk factor.

AKI from TLS is usually REVERSIBLE, even if hemodialysis is required (needed in ~1 in 6 patients) — an important prognostic point for family counseling, distinguishing TLS-AKI from many other causes of critical-illness AKI with less certain recovery.

2. Clinical Manifestations

Secondary to the metabolic derangements: cardiac arrhythmias (hyperkalemia-driven), mental status changes, stupor, renal failure, tetany (hypocalcemia), cardiac arrest. Any patient at risk requires frequent electrolyte, LDH, and uric acid monitoring, particularly around chemotherapy initiation for acute leukemia/high-grade lymphoma.

3. Risk Stratification

Patients are categorized low, intermediate, or high risk based on malignancy type, laboratory data, and pre-existing renal insufficiency — this stratification directly determines the prophylactic strategy (Section 4): allopurinol for low-intermediate risk; rasburicase for high risk or those with impaired cardiac/renal function and pretreatment uric acid >8 mg/dL.

4. Immediate Stabilization / Prevention-Focused Management

Management of AT-RISK patients focuses on PREVENTION — the entire protocol philosophy is proactive, not reactive.

Hydration (the cornerstone, both preventive AND therapeutic):

• High-risk patients: aggressive volume replacement BEFORE chemotherapy, isotonic fluid at 200-300 mL/h (or 3 L/m2/day, ~200 mL/kg/day if <=10kg pediatric dosing), adapted to age/cardiac function/urine output
• Increasing urinary flow rate is the MOST EFFECTIVE strategy for preventing urate-induced obstructive uropathy
• Target urine output 80-100 mL/m2/h (4-6 mL/kg/h); target urine specific gravity <=1.010
• Diuretics used CAUTIOUSLY to maintain urine output — CONTRAINDICATED if hypovolemia or obstructive uropathy is present (do not diurese a volume-depleted or obstructed patient)
• Urine ALKALINIZATION is NOT RECOMMENDED (a notable, actively-reversed older teaching) — no more effective than volume expansion alone, and can promote calcium phosphate deposition and, if combined with allopurinol, xanthine crystal formation causing tubular obstruction — avoid this once-standard practice

Checklist:

5. Uric-Acid-Lowering Therapy

Allopurinol (xanthine oxidase inhibitor, blocks uric acid production from hypoxanthine/xanthine):

• Indicated for intermediate-risk patients with pretreatment uric acid <8 mg/dL
• Dosing: 300-600 mg/day PO divided (pediatric: 50-100 mg/m2 q8h, max 300 mg/m2/day, or IV 200-400 mg/m2/day if oral not feasible)
• Start at least 24 hours PRIOR to chemotherapy where possible
• Dose-reduce for renal impairment
• Numerous drug interactions: 6-mercaptopurine, azathioprine, thiazides, amoxicillin, cyclophosphamide, methotrexate all require dose adjustment when combined
• A marked increase in xanthine excretion can occur with allopurinol use for TLS prophylaxis, itself risking acute renal failure or xanthine stones — a paradoxical risk of the preventive therapy itself
• Febuxostat as an alternative if allopurinol hypersensitivity
• Restrict allopurinol to LOW-INTERMEDIATE risk; established/high-risk TLS needs additional measures (rasburicase)

Rasburicase (recombinant urate oxidase, breaks down ALREADY-FORMED uric acid into allantoin, 5-10x more soluble):

• Indicated for HIGH-RISK patients, or those with impaired cardiac/renal function and pretreatment uric acid >8 mg/dL
• Dosing: 0.1-0.2 mg/kg/day IV in 50mL normal saline over 30 min, typically for up to 5 days (adjust per uric acid response)
• Serum/urinary uric acid decrease markedly within ~4 hours — rapid onset compared to allopurinol's several-day effect
• CONTRAINDICATED in G6PD deficiency — risk of severe hemolysis
• If emergent administration is needed and G6PD results are not urgently available: can give a LOW dose (0.02-0.05 mg/kg) with provision for urgent dialysis in case hemolysis occurs — a pragmatic compromise for true emergencies
• Sample handling caveat: rasburicase continues to degrade uric acid WITHIN blood samples at room temperature after collection, artificially lowering the measured level — samples must be placed on ICE IMMEDIATELY until assay completion to get an accurate reading
• Adverse reactions: anaphylaxis, rash, hemolysis, methemoglobinemia

6. Electrolyte Management

Hyperkalemia: standard therapies (calcium for cardioprotection, insulin/dextrose, albuterol — see Hyperkalemia protocol for full detail) plus hemodialysis if renal insufficiency or volume overload present.

Hypocalcemia: if ASYMPTOMATIC, NO THERAPY IS REQUIRED — an important restraint principle, since aggressive calcium repletion in the setting of concurrent hyperphosphatemia can worsen calcium-phosphate precipitation and tissue deposition; treat only if symptomatic or ECG changes present, with calcium gluconate/chloride slow IV and ECG monitoring.

Hyperphosphatemia: hydration, phosphate binders (aluminum hydroxide — limit to 1-2 days given cumulative aluminum toxicity risk — or calcium carbonate, sevelamer hydroxide, lanthanum carbonate), restrict phosphate intake; dialysis if severe.

7. Hemodialysis Indications (TLS-Specific)

Consider dialysis for: volume overload; uric acid >10 mg/dL DESPITE rasburicase; uncontrolled hyperkalemia/hyperphosphatemia; calcium x phosphate product >70 (a specific precipitation-risk threshold); established renal failure. CRRT preferred over intermittent dialysis where hemodynamic instability is a concern (same general principle as the AKI/CRRT protocols).

8. Organ Support

Aggressive isotonic hydration (the primary preventive/therapeutic intervention); hemodialysis/CRRT per indications above; electrolyte management per Section 6; standard ICU supportive care during active tumor lysis.

9. Consultation Matrix

10. Monitoring Framework

Frequent electrolytes (K+, phosphate, calcium, uric acid) — more frequent than standard ICU labs given the rapid kinetics of TLS, LDH trend, renal function trend, urine output/specific gravity, continuous cardiac monitoring given arrhythmia risk from rapid electrolyte shifts.

11. Complications

Cardiac arrhythmia/arrest (hyperkalemia-driven), AKI (though typically reversible), tetany/seizure (hypocalcemia), calcium-phosphate precipitation/tissue deposition, allopurinol-associated xanthine nephropathy, rasburicase-associated hemolysis (G6PD deficiency) or anaphylaxis. Prevention: proactive risk stratification and prophylaxis BEFORE chemotherapy, avoiding urine alkalinization, careful rasburicase G6PD screening where feasible, judicious (not reflexive) calcium repletion. Rescue: hemodialysis/CRRT per indications, standard hyperkalemia rescue therapy, hemolysis management if rasburicase-triggered.

12. Escalation & De-escalation

Escalate: dialysis indication criteria met (Section 7) -> initiate CRRT/IHD; uric acid remaining elevated despite allopurinol -> escalate to rasburicase.

De-escalate: electrolytes normalizing, uric acid controlled, urine output adequate, LDH trending down -> liberalize fluid rate, transition off prophylactic dosing schedule, resume standard oncologic monitoring.

13. ICU Discharge Criteria

Electrolytes stable/normalized, uric acid controlled, no ongoing dialysis need (or established outpatient dialysis plan if renal recovery incomplete), chemotherapy plan proceeding per oncology with appropriate ongoing TLS surveillance if further cycles planned.

14. Documentation & Medicolegal Checklist

15. Key Guidelines

Coiffier B, Altman A, Pui CH, Younes A, Cairo MS. Guidelines for the management of pediatric and adult tumor lysis syndrome: an evidence-based review. J Clin Oncol. 2008;26:2767-2778 — primary evidence-based reference (Cairo-Bishop framework).

16. Landmark Evidence

Howard SC, Trifilio S. Tumor lysis syndrome in the era of novel and targeted agents in patients with hematologic malignancies: a systematic review. Ann Hematol. 2016;95(4):563-573 — highlights TLS risk with newer targeted agents (including CAR-T therapy) beyond traditional cytotoxic chemotherapy.

17. Controversies

Multiple TLS management guidelines exist, but NO studies have directly compared outcomes between them — all guidelines emphasize early recognition and aggressive treatment as the common thread, but the specific prophylaxis thresholds/agent choices vary somewhat across society recommendations. The precise timing and duration of rasburicase dosing (fixed 5-day course vs response-guided shorter courses) is not tightly standardized and varies by institutional protocol and cost considerations. TLS risk with newer immunotherapy/targeted agents (CAR-T, bispecific antibodies) is an evolving area distinct from traditional cytotoxic-chemotherapy-triggered TLS, with less mature risk-stratification data.

18. References

1. Kulkarni A, Agarwal V. Onco-emergencies (Tumor Lysis Syndrome). ICU Protocols: A Step-wise Approach, 2nd ed. Springer; 2020 (Ch. 9).
2. Neuro-Oncologic and Hematologic Emergencies chapter (TLS section). Washington Manual of Critical Care, 4th ed, 2025 (Ch. 33 region).
3. Coiffier B, Altman A, Pui CH, Younes A, Cairo MS. Guidelines for the management of pediatric and adult tumor lysis syndrome: an evidence-based review. J Clin Oncol. 2008;26:2767-2778.
4. Howard SC, Trifilio S. Tumor lysis syndrome in the era of novel and targeted agents. Ann Hematol. 2016;95(4):563-573.
5. Alakel N, Middeke JM, Schetelig J, Bornhauser M. Prevention and treatment of tumor lysis syndrome, and the efficacy and role of rasburicase. Onco Targets Ther. 2017;10:597-605.

See also: Hyperkalemia, Acute Kidney Injury, CRRT Indications (Renal System) for the shared electrolyte and renal support management this syndrome requires; Brain Tumors (Neurology System) for related neuro-oncologic emergencies including CAR-T-associated ICANS.