Tumor Lysis Syndrome Diagnosis and Management

Diagnostic Criteria

The European Hematology Association defines laboratory tumor lysis syndrome (TLS) by the presence of two or more abnormal serum values, including hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia, within three days before or seven days after the start of anticancer treatment 1, 2, 3
Uric acid levels are considered elevated if they increase by >25% from baseline or reach absolute values ≥476 mmol/L (8 mg/dL) 1, 2
Potassium levels are considered elevated if they increase by >25% from baseline or reach absolute values ≥6.0 mmol/L (6 mEq/L) 1, 2
Phosphorus levels are considered elevated if they increase by >25% from baseline or reach absolute values ≥1.45 mmol/L (4.5 mg/dL) in adults and ≥2.1 mmol/L (6.5 mg/dL) in children 1, 2
Calcium levels are considered decreased if they decrease by >25% from baseline or reach absolute values ≤1.75 mmol/L (7 mg/dL) 1, 2

Clinical TLS is diagnosed when laboratory TLS is accompanied by at least one of the following clinical complications: renal failure (eGFR ≤60 mL/min), cardiac arrhythmias, or seizures 1, 3, 4
The glomerular filtration rate (eGFR) should be calculated using one of the following formulas: MDRD formula or Cockroft-Gault equation 1, 2, 3
Tumor-related factors that increase the risk of developing TLS include hematologic malignancies with high proliferation rates and high tumor burden 1, 5, 6
Patient-related factors that increase the risk of developing TLS include pre-existing elevated uric acid levels, pre-existing renal dysfunction, advanced age, and tumor infiltration in the kidney 1, 6
Treatment-related factors that increase the risk of developing TLS include highly active, cycle-specific chemotherapeutic agents and corticosteroid therapy in lymphoid malignancies 1, 6

The European Hematology Association recommends monitoring LDH, uric acid, sodium, potassium, creatinine, BUN, phosphorus, and calcium every 12 hours for the first three days, then every 24 hours subsequently in high-risk patients before TLS develops 7
In established TLS patients, the European Hematology Association suggests monitoring vital signs, serum uric acid level, serum electrolytes, and renal function every 6 hours for the first 24 hours, then daily thereafter 7
Additional parameters such as complete blood count, serum LDH, albumin, serum osmolality, blood gases and acid-base equilibrium, electrocardiogram, and body weight should be assessed every 24 hours in established TLS patients 7
The European Hematology Association recommends monitoring urine output closely, maintaining at least 100 mL/hour in adults (3 mL/kg/hour in children <10 kg), and measuring urine osmolality and fractional excretion of sodium to define hydration status 7

The European Hematology Association advises against using calcium gluconate to correct mild hypocalcemia, as it increases tissue and renal calcium phosphate precipitation 7

Tumor lysis syndrome (TLS) is diagnosed when ≥ 2 metabolic abnormalities (hyperuricemia, hyperkalemia, hyperphosphatemia, or hypocalcemia) occur within ‑3 days to +7 days of initiating anticancer therapy; clinical TLS requires laboratory TLS plus at least one major complication (renal failure, cardiac arrhythmia, or seizure)【8】.

Hyperuricemia – serum uric acid ≥ 476 µmol/L (8 mg/dL) in adults, or an increase > 25 % from a recent baseline【8】.
Hyperkalemia – serum potassium ≥ 6.0 mmol/L (6 mEq/L), or an increase > 25 % from baseline【8】.
Hyperphosphatemia – serum phosphorus ≥ 1.45 mmol/L (4.5 mg/dL) in adults and ≥ 2.1 mmol/L (6.5 mg/dL) in children, or an increase > 25 % from baseline【8】.
Hypocalcemia – corrected calcium ≤ 1.75 mmol/L (7 mg/dL), or a decrease > 25 % from baseline【8】.

Renal failure – estimated glomerular filtration rate (eGFR) ≤ 60 mL/min, calculated with the MDRD or Cockcroft‑Gault equations rather than serum creatinine alone【8】.
Cardiac complications – life‑threatening arrhythmias such as ventricular tachycardia, ventricular fibrillation, or cardiac arrest【9】【8】.
Neurological complications – seizures, which may be precipitated by hypocalcemia or other metabolic disturbances【8】【9】.

The diagnostic window for TLS spans ‑3 days to +7 days relative to the start of anticancer treatment【8】.
Spontaneous TLS can arise before chemotherapy in highly proliferative malignancies (e.g., aggressive lymphomas, acute leukemias)【9】.
The majority of cases present 12–72 hours after cytoreductive therapy begins【9】.
Extending observation to 7 days post‑treatment captures delayed presentations【8】.

Patients with a baseline uric acid ≥ 8 mg/dL have an ≈ 11.7‑fold increased risk of developing TLS compared with those whose baseline uric acid is < 4 mg/dL【9】.
A ≥ 25 % change (increase for uric acid, potassium, phosphorus; decrease for calcium) from baseline qualifies as an abnormal value even when absolute thresholds are not met【8】.
Reliance on serum creatinine alone is insufficient for renal assessment; eGFR calculation is mandatory【8】.
Recognizing that only two of the four metabolic derangements are needed for laboratory TLS prevents delayed diagnosis【8】.

Laboratory TLS without clinical complications is not graded—it is recorded as present or absent【9】【8】.
When clinical complications occur, the grade is determined by the most severe manifestation (e.g., severity of renal failure, type of arrhythmia, or occurrence of seizure)【9】.