What is tumor lysis syndrome?

What is Tumor Lysis Syndrome?

Tumor lysis syndrome (TLS) is a potentially life-threatening oncologic emergency characterized by massive and abrupt release of intracellular contents into the bloodstream following rapid lysis of malignant cells, resulting in severe metabolic derangements that can lead to acute kidney injury, cardiac arrhythmias, seizures, and death. 1

Pathophysiology

TLS occurs when large numbers of tumor cells break down rapidly, overwhelming the body's normal homeostatic mechanisms. This massive cellular destruction releases:

• Nucleic acids (metabolized to uric acid, causing hyperuricemia)
• Potassium (causing hyperkalemia)
• Phosphorus (causing hyperphosphatemia)
• Proteins and other intracellular metabolites

The hyperphosphatemia subsequently leads to hypocalcemia through calcium-phosphate binding. 1, 2

Clinical Context and Risk Factors

TLS is observed most frequently in:

• Hematologic malignancies with high proliferative rates, particularly:

  • Acute lymphoblastic leukemia (ALL)
  • Burkitt's lymphoma
  • High-grade non-Hodgkin's lymphomas

• After initiation of cytotoxic therapy, though it can occur spontaneously in tumors with:

  • Large tumor burden (≥500 g or ≥300 g/m² body surface area in children) 2
  • High proliferative rate
  • High sensitivity to chemotherapy 1, 3

While traditionally associated with hematologic cancers, TLS incidence is increasing in solid tumors due to highly effective biologic and targeted therapies. 4

Metabolic Consequences

The characteristic metabolic abnormalities include:

• Hyperuricemia: Uric acid crystallizes in renal collecting ducts and vessels, causing acute oliguric renal failure
• Hyperkalemia: Can cause life-threatening cardiac arrhythmias
• Hyperphosphatemia: Calcium phosphate complexes deposit in renal interstitium, exacerbating kidney damage
• Hypocalcemia: Results from calcium-phosphate binding
• Uremia: From acute kidney injury 1, 5

Clinical Manifestations and Organ Damage

The syndrome can progress to overt organ damage including:

• Cardiac arrhythmias (from hyperkalemia and hypocalcemia)
• Seizures (from hypocalcemia and metabolic derangements)
• Acute kidney injury and renal failure
• Multi-organ failure
• Death if untreated 3, 2

Classification

TLS has been subclassified into:

• Laboratory TLS: Metabolic abnormalities without clinical symptoms
• Clinical TLS: Laboratory abnormalities plus clinical manifestations (renal dysfunction, cardiac arrhythmias, seizures, or death) 1

A grading system exists to stratify severity and guide management. 1

Critical Timing

TLS usually occurs shortly after initiation of effective cytotoxic therapy, though spontaneous TLS can occur before treatment in highly aggressive or bulky tumors. 2, 6 The syndrome represents a medical emergency requiring immediate recognition and intervention to prevent mortality.