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Cancer-Related Medical Emergencies: Acute Tumor Lysis Syndrome
(More PulmCCM Topic Updates)
The prevalence of multiple cancers are expected to rise in the United States over the coming decades. Despite improved survival with some cancers, some people with malignancy will develop cancer related emergencies; for a few, this will be the first manifestation of their cancer. It's important to be able to recognize and treat these oncologic emergencies; some key points on acute tumor lysis syndrome are highlighted here.
Acute Tumor Lysis Syndrome
What It Is: Severe metabolic derangement caused by the release of intracellular contents from malignant cells rapidly dying after recent cancer treatment.
When to Consider It: High-grade non-Hodgkin lymphoma and acute lymphocytic leukemia after any form of cancer treatment. Spontaneous tumor lysis syndrome (in the absence of recent cancer treatment) can occur in aggressive lymphomas and leukemias (Burkitt lymphoma, acute lymphocytic leukemia, large T-cell lymphoma). TLS is uncommon in solid tumors but can occur in testicular cancer, small cell lung cancer, neuroblastoma, and breast cancer. Renal failure is a predisposing factor. Any type of cancer treatment can precipitate tumor lysis syndrome--including glucocorticoids, radiation therapy and tamoxifen--as well as systemic chemotherapy.
What to Watch Out For: Hyperkalemia, hyperphosphatemia, hypocalcemia (caused by binding with excess phosphate), and hyperuricemia. Hyperkalemia may cause cardiac arrhythmias; excess phosphate and uric acid may cause or worsen renal failure. Acute kidney injury during acute tumor lysis syndrome is an independent an important marker for mortality risk.
Acute Tumor Lysis Syndrome: What to Do
Give Intravenous Volume: Upon the first suspicion for acute tumor lysis syndrome, authors recommend aggressive intravenous fluids at twice the expected maintenance rate.
Don't Alkalinize Urine: Authors do not recommend alkalinization of the urine (to increase uric acid solubility) because it may precipitate calcium phosphate and xanthine crystals, which can worsen nephropathy.
Hyperkalemia: with Kayexalate, insulin/dextrose, sodium bicarbonate (cautiously to avoid inadvertent hyperkalemia, metabolic alkalosis, or the creation of calcium crystals), calcium gluconate.
Hyperphosphatemia: Flushing with intravenous fluids; give phosphate binders as needed. Renal replacement therapy may be considered in severe cases or when medical management fails.
Hypocalcemia: Should not be treated unless symptoms are present, to avoid the risk of nephropathy, authors say.
Hyperuricemia: Rasburicase (recombinant urate oxidase) catabolizes uric acid and rapidly normalizes uric acid levels; authors recommend rasburicase as first-line therapy for patients with tumors prone to rapid lysis or who have acute tumor lysis syndrome with pre-existing renal failure and high uric acid levels. Rasburicase is contraindicated in patients with G6PD deficiency, and whom it can cause hemolytic anemia or methemoglobinemia. Rasburicase is currently recommended on faith and its plausible mechanism; no randomized trial has shown that it prevents real failure or death. Allopurinol is used prophylactically before chemotherapy, but is not recommended for acute tumor lysis syndrome.
Acute Kidney Injury: Renal replacement therapy (dialysis) is recommended for patients with acute tumor lysis syndrome and significant acute kidney injury, who are not responding well to medical management, or who have potentially life-threatening electrolyte disturbances. No one knows if hemodialysis or continuous renal replacement is a superior method.
McCurdy MT, Shanholtz CB. Oncologic emergencies. Crit Care Med 2012;40:2212-2222.