What is tumor lysis syndrome?

Related conditions:
Acute renal failure, arrhythmias, metabolic acidosis

Definition:
Tumor lysis syndrome is a potentially life-threatening metabolic emergency caused when tumor cells are destroyed and broken down faster than the body can get rid of them. This causes an increase in various electrolyte levels in the blood, which can lead to renal failure. The cancer cells may be destroyed by chemotherapy, radiation, or the disease process itself. The complication may be categorized as laboratory tumor lysis syndrome (LTLS), in which no symptoms are present, or as clinical tumor lysis syndrome (CTLS), featuring both laboratory and clinical symptoms.

Risk factors: People at risk are those who are diagnosed with a rapidly growing cancer that responds well to chemotherapy. Some cancers that place patients at risk for tumor lysis syndrome are leukemia, non-Hodgkin lymphoma, Burkitt lymphoma, soft-tissue sarcoma, small-cell lung cancer, and medulloblastomas. The more involved or aggressive the disease is, the more the risk for developing tumor lysis syndrome. Other risk factors include high levels of serum lactate dehydrogenase (LDH), tumors that affect genitourinary function, increased age, and dehydration.

People who have preexisting kidney failure are also at increased risk for developing tumor lysis syndrome.

Etiology and the disease process: Chemotherapy causes the patient’s cancer cells to lyse, or break down, releasing the contents of the cancer cell into the bloodstream. This causes an increase in the serum potassium, phosphate, and uric acid levels and a decrease in the calcium levels. The levels change at such a rapid rate that the body is unable to maintain a balance and potentially lethal symptoms arise. Tumor lysis syndrome is most common within a week of the initiation of cancer treatment, but can happen at other times as well.

Incidence: The exact incidence of tumor lysis syndrome is not known, though it is estimated to occur in 5 to 20 percent of all cancer patients. Patients who are diagnosed with leukemia in blast crisis have a higher incidence of tumor lysis syndrome. It is more commonly seen with hematologic cancers than those with solid tumors.

Symptoms: Symptoms include the following changes in blood values:

• Hyperkalemia: Increased levels of potassium in the blood. Normal potassium levels are about 3.5 to 5.0 millimoles/deciliter (mmol/dl). In tumor lysis, the potassium will increase to greater than 6 mmol/dl. Symptoms commonly associated with an increase in potassium levels are muscle weakness, muscle cramps, and paralysis. High potassium levels also contribute to cardiac problems including a racing heart rate, decrease in heart rate, and sudden death. Additional symptoms associated with high potassium levels include nausea, vomiting, diarrhea, and loss of appetite.





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  Hyperphosphatemia: Increased levels of phosphorus in the blood. Cancer cells contain about four times more phosphorus than normal cells. When the cancer cells are killed, the phosphorus is released into the blood. This increased level of phosphate can cause the kidneys to misfunction and can cause acute renal failure. The increase in the phosphorus combines with the increased calcium levels and affects the kidney and muscle tissue. This causes a rapid decrease in calcium levels, which can then cause the patient to experience severe muscle cramping and twitching, and problems with the heart.





• Hypocalcemia: Calcium deficiency in the blood. When phosphate increases, the calcium decreases. Symptoms of hypocalcemia can include seizures, Parkinson-like movements, swelling of the optic disk, agitation or anxiety, painful muscle spasms, and muscle weakness.





• Hyperuricemia: Increased levels of uric acid in the blood. This can cause acute renal failure. Symptoms may include nausea and vomiting, diarrhea, and loss of appetite.

Screening and diagnosis: Patients who are at high risk of developing tumor lysis syndrome should have baseline labs drawn before therapy begins. Many times patients may not exhibit any signs and symptoms but will begin to have altered lab values. It is important that the patient who is at risk have frequent blood tests taken to monitor for changes. Blood tests should monitor calcium, potassium, phosphate, magnesium, and uric acid levels.

Treatment and therapy: The best treatment is prevention. Treatment is targeted to the altered laboratory value as well as symptoms as they arise. Intravenous (IV) fluids should be initiated in patients before therapy begins and continue to be infused throughout therapy. If high flow rate is used for IV fluids, then a diuretic, such as furosemide (Lasix), may be added to assist with urine excretion. Patients are also given allopurinol, an antigout medication, to stop the formation of uric acid. Urine alkalization may be done by adding sodium bicarbonate to the IV fluids. More severe cases of tumor lysis syndrome may require kidney dialysis to help support the patient through the crisis. The dialysis helps remove the excess potassium and phosphorus when the patient’s kidneys are unable to do so.

Patients who have increased potassium levels are treated with sodium polystyrene (Kayexalate). Sodium polystyrene draws the potassium into the bowel to be excreted. Diuretics can also be used to help eliminate the potassium in the urine. In severe cases of elevated potassium, patients are treated with insulin and dextrose, which causes the cells to take in more potassium, decreasing the potassium levels in the blood.

Increased phosphorus is treated with oral doses of aluminum hydroxide. Aluminum hydroxide will draw the phosphorus into the bowel to be excreted. Diuretics can also be given to increase the amount of phosphorus excreted in the urine. Decreasing the phosphorus level also causes the calcium level to increase.

Low calcium levels are not typically treated unless the patient becomes symptomatic, and then the patient receives calcium gluconate.

Prognosis, prevention, and outcomes: Tumor lysis may be prevented by administering intravenous fluids and allopurinol. Tumor lysis syndrome can occur rapidly, within hours, and have a poor prognosis. As lab values can start changing before the patient experiences side effects, patients who are at risk for tumor lysis syndrome should be hospitalized with preventive therapy initiated, allowing for aggressive treatment to start before the patient’s condition worsens.

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