Oncologic emergency from rapid tumor cell breakdown producing hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and AKI.
Also known as: TLS, tumor lysis, tumor lysis syndrome
Overview
Oncologic emergency caused by massive release of intracellular contents (potassium, phosphate, nucleic acids) from rapidly lysing tumor cells, leading to characteristic metabolic derangements (hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia) and downstream complications including acute kidney injury, cardiac arrhythmias, seizures, and death.
Epidemiology
Occurs most commonly with high-grade hematologic malignancies (Burkitt lymphoma, ALL, AML with high WBC, DLBCL) following initiation of chemotherapy or other cytotoxic therapy. May occur spontaneously (rare) in highly proliferative tumors. Solid tumor TLS is uncommon but reported in small cell lung cancer, germ cell tumors, and metastatic breast cancer.
Try two board-style Tumor Lysis Syndrome questions
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Question 1HematologyMedium
A 24-year-old man with newly diagnosed Burkitt lymphoma and bulky abdominal disease begins his first cycle of chemotherapy. Pre-treatment WBC was 80 × 10⁹/L with an LDH more than three times the upper limit of normal. Approximately 36 hours after the first dose, he develops nausea, muscle cramps, and decreased urine output. Vitals are stable. Labs show potassium 6.4 mEq/L, phosphate 6.8 mg/dL, calcium 6.6 mg/dL, uric acid 11 mg/dL, and creatinine rising from 0.9 to 1.8 mg/dL. Telemetry shows peaked T waves. Which of the following is the most likely diagnosis?
ARhabdomyolysis-induced acute kidney injury
BTumor lysis syndrome with acute kidney injury
CCisplatin-induced acute tubular necrosis
DMethotrexate-induced acute crystal nephropathy
Reveal answer & full explanation
Correct answer: B — Tumor lysis syndrome with acute kidney injury
ARhabdomyolysis-induced acute kidney injury
BTumor lysis syndrome with acute kidney injury✓
CCisplatin-induced acute tubular necrosis
DMethotrexate-induced acute crystal nephropathy
Why Tumor lysis syndrome with acute kidney injury is correct
A high-burden, highly chemosensitive malignancy (Burkitt lymphoma, WBC 80 × 10⁹/L, LDH >3x ULN) developing acute metabolic derangements within 12-72 hours of starting cytotoxic therapy is the classic setup for TLS.
The labs satisfy Cairo-Bishop laboratory criteria (>=2 of: uric acid >=8, K >=6, phosphate >=4.5, Ca <=7) — here all four are present — plus a creatinine >=1.5x baseline and an arrhythmia risk (peaked T waves), making this clinical TLS.
Mechanism: massive cell lysis dumps intracellular K, phosphate, and nucleic acids; uric acid and calcium-phosphate crystallize in renal tubules causing AKI, while calcium falls as it binds the excess phosphate.
Why the others are wrong
Rhabdomyolysis-induced acute kidney injury also causes hyperkalemia and hyperphosphatemia, but is driven by muscle breakdown with a markedly elevated CK and myoglobinuria, and does not produce the hyperuricemia surge or fit the post-chemotherapy timeline.
Cisplatin-induced acute tubular necrosis can raise creatinine, but it causes isolated AKI (often with magnesium wasting) rather than the simultaneous hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia cascade; cisplatin is also not the agent used for Burkitt lymphoma.
Methotrexate-induced acute crystal nephropathy can crystallize in tubules and cause AKI, but it presents with the offending drug exposure and lacks the full electrolyte cascade and uric acid spike seen here.
Question 2HematologyMedium
A 19-year-old man is admitted for induction chemotherapy of newly diagnosed acute lymphoblastic leukemia with a presenting WBC of 180 × 10⁹/L and an LDH 4 times the upper limit of normal. Thirty-six hours after the first dose of cytotoxic therapy, he develops oliguria, muscle cramps, and perioral paresthesias. His creatinine has risen from 0.9 to 2.1 mg/dL, and telemetry shows peaked T waves. Serum studies are drawn to confirm the suspected oncologic emergency. Which of the following laboratory findings best supports the diagnosis?
ASerum calcium level 6.4 mg/dL
BSerum sodium level 122 mEq/L
CSerum bicarbonate level 32 mEq/L
DSerum creatine kinase 9,800 U/L
Reveal answer & full explanation
Correct answer: A — Serum calcium level 6.4 mg/dL
ASerum calcium level 6.4 mg/dL✓
BSerum sodium level 122 mEq/L
CSerum bicarbonate level 32 mEq/L
DSerum creatine kinase 9,800 U/L
Why Serum calcium level 6.4 mg/dL is correct
Tumor lysis syndrome (TLS) is defined by the Cairo-Bishop laboratory criteria: ≥2 of hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia within 3 days before to 7 days after chemotherapy initiation.
Released intracellular phosphate binds serum calcium and precipitates as calcium phosphate, producing reciprocal hypocalcemia (calcium ≤7 mg/dL); this explains the cramps, perioral paresthesias, and risk of tetany/seizures.
Combined with this patient's high tumor burden (WBC 180 × 10⁹/L, LDH 4× ULN), new AKI, and hyperkalemic ECG changes 36 h after chemo, hypocalcemia completes the diagnostic metabolic tetrad of TLS.
Why the others are wrong
Serum bicarbonate level 32 mEq/L — indicates a metabolic alkalosis; TLS typically produces a metabolic acidosis from AKI, so this points away from the diagnosis rather than supporting it.
Serum sodium level 122 mEq/L — hyponatremia is nonspecific and not part of the Cairo-Bishop criteria; it is a common but non-discriminating finding in hospitalized oncology patients.
Serum creatine kinase 9,800 U/L — a markedly elevated CK indicates rhabdomyolysis, a TLS mimic that shares hyperkalemia and hyperphosphatemia but lacks the uric acid surge and is not part of TLS criteria.
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Cardiac arrhythmias on telemetry — peaked T waves, prolonged QRS in hyperkalemia
Prolonged QT in hypocalcemia
Volume overload from AKI; uremic signs
Classic findings
Patient with bulky lymphoma or hyperleukocytic leukemia who within 12-72 hours of starting chemotherapy develops oliguria, hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia.
Differential diagnosis
Acute kidney injury from chemotherapy nephrotoxicity — Cisplatin, methotrexate, ifosfamide; usually no electrolyte cascade of TLS
Sepsis with multi-organ dysfunction — Hypotension, lactic acidosis, positive cultures; may overlap with TLS in hematologic patients
Rhabdomyolysis — CK markedly elevated, myoglobinuria; hyperkalemia and hyperphosphatemia overlap but no uric acid surge
Hyperleukocytosis / leukostasis — WBC >100 × 10⁹/L with respiratory/neurologic symptoms; may coexist with TLS in AML/ALL
Crystal nephropathies — Methotrexate, acyclovir, sulfonamides crystals in tubules; drug exposure history
Diagnostic workup
Diagnostic criteria
Cairo-Bishop criteria — Laboratory TLS = ≥2 of the following within 3 days before or 7 days after chemotherapy initiation:
- Uric acid ≥8 mg/dL or 25% increase from baseline
- Potassium ≥6 mEq/L or 25% increase
- Phosphate ≥4.5 mg/dL (adult) / ≥6.5 (pediatric) or 25% increase
- Calcium ≤7 mg/dL or 25% decrease
Clinical TLS = Laboratory TLS PLUS ≥1: creatinine ≥1.5x ULN, cardiac arrhythmia/sudden death, or seizure.
Pre-chemotherapy labs and frequent monitoring (every 4-6 h x 24-48 h, then daily) in high-risk patients
Imaging
Renal ultrasound if AKI and concern for obstruction or hydronephrosis
ECG — assess hyperkalemia and hypocalcemia changes
Treatment
First-line
PREVENTION is the cornerstone — risk-stratify all patients before initiating cytotoxic therapy
Aggressive IV hydration — isotonic crystalloid (0.9% NaCl or balanced) targeting urine output 80-100 mL/m²/h; start 24-48 h before chemo when possible
Allopurinol (xanthine oxidase inhibitor) — oral 100 mg/m² q8h or IV — for low-to-intermediate risk; start 24-48 h before chemo and continue 3-7 days
Rasburicase (recombinant urate oxidase) — preferred for high-risk patients or established hyperuricemia; 0.2 mg/kg IV daily; CONTRAINDICATED in G6PD deficiency (causes severe hemolysis and methemoglobinemia)
Frequent electrolyte monitoring (q4-6h in high-risk patients)
Cardiac arrhythmias and sudden cardiac death from hyperkalemia
Seizures and tetany from hypocalcemia
Need for renal replacement therapy
Multi-organ dysfunction
Mortality 15-30% in clinical TLS
PANCE pearls
Rasburicase is contraindicated in G6PD deficiency — causes severe hemolysis and methemoglobinemia.
Urinary alkalinization is no longer recommended — it promotes calcium phosphate precipitation in tubules.
Calcium replacement should be reserved for symptomatic hypocalcemia or ECG changes — empiric calcium worsens calcium phosphate deposition.
Venetoclax in CLL requires a 5-week ramp-up dosing schedule and aggressive TLS prophylaxis to minimize this complication.
Spontaneous TLS (before any therapy) suggests extremely high tumor burden — consider in Burkitt and aggressive AML.
Rasburicase samples for uric acid must be collected and transported cold; otherwise ex vivo degradation falsely lowers reported uric acid.
References
Cairo-Bishop criteria — Cairo MS, Bishop M. Tumour lysis syndrome: new therapeutic strategies and classification. Br J Haematol 2004; 127:3-11.
BCSH Guidelines — Jones GL et al. Guidelines for the management of tumour lysis syndrome in adults and children with haematological malignancies. Br J Haematol 2015; 169:661-671.
NCCN — NCCN Clinical Practice Guidelines in Oncology: B-cell lymphomas and CLL/SLL (TLS sections).
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