Tumor lysis syndrome | |
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Specialty | Oncology, hematology |
Tumor lysis syndrome (TLS) is a group of metabolic abnormalities that can occur as a complication from the treatment of cancer, where large amounts of tumor cells are killed off (lysed) from the treatment, releasing their contents into the bloodstream. [1] This occurs most commonly after the treatment of lymphomas and leukemias and in particular when treating non-Hodgkin lymphoma, acute myeloid leukemia, and acute lymphoblastic leukemia. [2] [3] This is a potentially fatal complication and people at an increased risk for TLS should be closely monitored while receiving chemotherapy and should receive preventive measures and treatments as necessary. [4] [3] TLS can also occur on its own (while not being treated with chemotherapy) although this is less common. [4] [5]
Tumor lysis syndrome is characterized by high blood potassium (hyperkalemia), high blood phosphate (hyperphosphatemia), low blood calcium (hypocalcemia), high blood uric acid (hyperuricemia), and higher than normal levels of blood urea nitrogen (BUN). [4] These changes in blood electrolytes and metabolites are a result of the release of cellular contents of dying cells into the bloodstream. [4] In this respect, TLS is analogous to rhabdomyolysis, with comparable mechanism and blood chemistry effects but with different cause. In TLS, the breakdown occurs after cytotoxic therapy or from cancers with high cell turnover and tumor proliferation rates. [4] The metabolic abnormalities seen in tumor lysis syndrome can ultimately result in serious complications such as acute uric acid nephropathy, acute kidney failure, seizures, cardiac arrhythmias, and death. [6] [7]
Acute uric acid nephropathy (AUAN) due to hyperuricosuria has been a dominant cause of acute kidney failure, but with the advent of effective treatments for hyperuricosuria, AUAN has become a less common cause than hyperphosphatemia. [ citation needed ] Two common conditions related to excess uric acid, gout and uric acid nephrolithiasis, are not features of tumor lysis syndrome.[ citation needed ]
Risk factors for tumor lysis syndrome depend on several different characteristics of the patient, the type of cancer, and the type of chemotherapy used. [14]
Tumor characteristics: Tumors with a high cell turnover rate, rapid growth rate, and high tumor bulk tend to be more associated with the development of tumor lysis syndrome. The most common tumors associated with this syndrome are poorly differentiated lymphomas (such as Burkitt's lymphoma), other Non-Hodgkin Lymphomas (NHL), acute lymphoblastic leukemia (ALL), and acute myeloid leukemia (AML). [3] Other cancers (such as melanoma) have also been associated with TLS but are less common.
Patient characteristics: Certain patient-related factors can affect the development of clinical tumor lysis syndrome. These factors include elevated baseline serum creatinine, kidney failure, dehydration, and other issues affecting urinary flow or the acidity of urine. [14]
Chemotherapy characteristics: Chemo-sensitive tumors, such as lymphomas, carry a higher risk for the development of tumor lysis syndrome. Those tumors that are more responsive to a chemotherapy agent carry a higher TLS risk. [7] Usually, the precipitating medication regimen includes combination chemotherapy, but TLS can be triggered in cancer patients by steroid treatment alone, and sometimes without any treatment—in this case the condition is referred to as "spontaneous tumor lysis syndrome". [13]
TLS should be suspected in people with large tumor burden who develop acute kidney failure along with hyperuricemia (> 15 mg/dL) or hyperphosphatemia (> 8 mg/dL). [ medical citation needed ] (Most other acute kidney failure occurs with uric acid < 12 mg/dL and phosphate < 6 mg/dL). [ citation needed ] Acute uric acid nephropathy is associated with little or no urine output. [ citation needed ] The urinalysis may show uric acid crystals or amorphous urates. [ citation needed ] The hypersecretion of uric acid can be detected with a high urine uric acid - creatinine ratio > 1.0, compared to a value of 0.6–0.7 for most other causes of acute kidney failure.[ citation needed ]
In 2004, Cairo and Bishop defined a classification system for tumor lysis syndrome. [15]
A grading scale (0–5) is used depending on the presence of lab TLS, serum creatinine, arrhythmias, or seizures.
In 2011, Howard proposed a refinement of the standard Cairo-Bishop definition of TLS accounting for 2 limitations: [2]
Moreover, any symptomatic hypocalcemia should constitute clinical TLS. [2]
It is important to prevent life-threatening manifestations associated with TLS which include acute kidney injury, hyperkalemia (which may cause cardiac arrhythmias), and or hypocalcemia (which may cause cardiac arrhythmias and neuromuscular irritability). [2]
Acute kidney injury: Patients at risk for developing TLS (e.g. patients about to receive chemotherapy for a cancer with a high cell turnover rate, especially lymphomas and leukemias) should receive appropriate intravenous hydration in order to improve blood flow to the kidneys, maximize urine output, and ultimately prevent precipitation of uric acid crystals that can lead to acute kidney injury. [2] [4] A diuretic may also be indicated to further increase urine output in addition to intravenous hydration. [2] [4] Another approach to prevent damage to the kidneys is to prevent the buildup of uric acid during TLS, and this can be accomplished with use of allopurinol or rasburicase. [2] Allopurinol (a xanthine oxidase inhibitor, which inhibits uric acid production) works by preventing the formation of uric acid following tumor cell lysis. [4] [13] Rasburicase is a synthetic urate oxidase enzyme and acts by degrading uric acid. No current guidelines endorse the concurrent use of allopurinol and rasburicase. [16] [17] It is not recommended to alkalinize urine in the management of TLS: although doing so increases the solubility of urste, it also creates calcium phosphate crystals. [2] [4]
Hyperkalemia: Monitoring potassium levels in the blood frequently and cardiac monitoring (given the risk of cardiac arrhythmias) are important components in the prevention of adverse consequences in TLS. [2] Other strategies, such as limiting oral intake of potassium, and excreting potassium through the gastrointestinal tract using agents such as oral sodium polystyrene sulfonate, can be beneficial. [2] [4] Insulin therapy (in conjunction with glucose administration) as well as beta-receptor agonists (such as albuterol) can also be used, but are temporary interventions, [2] and potassium is not excreted from the body. [ citation needed ] Hemodialysis and hemofiltration can also be used as options to remove potassium from the bloodstream when hyperkalemia is present. [2]
Hypocalcemia: Hyperphosphatemia is a common finding in TLS, and high phosphorus levels can in turn contribute to hypocalcemia. Therefore, phosphate binders may be beneficial in preventing this form of hypocalcemia. [2]
Treatment is first targeted at the specific metabolic disorder.
In general, rasburicase and hydration are the mainstays of treatment in patients with clinical evidence of tumor lysis syndrome. [18] A loop diuretic may also be indicated to maintain appropriate production of urine by the kidneys. [18] Further treatment is targeted towards the specific metabolic abnormalities present in patients with TLS (see "main articles" linked above). Mild hyperkalemia without symptoms can be treated with a loop diuretic and sodium polystyrene sulfonate, while a temporizing agent such as rapid acting insulin (in conjunction with glucose) and an agent to stabilize cardiac membranes such as calcium carbonate may be given in cases of severe hyperkalemia. [18] Concerning symptoms related to hypocalcemia (e.g. seizures) in TLS patients can be treated with calcium gluconate. [18] Tumor lysis patients may ultimately also require renal replacement therapy such as through hemodialysis if indicated. [18]
The rate of mortality from tumor lysis syndrome may vary widely depending on the type of underlying malignancy. [19] However, the occurrence of acute kidney injury is concerning given the high mortality that is generally associated with it. [2]
Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a product of the metabolic breakdown of purine nucleotides, and it is a normal component of urine. High blood concentrations of uric acid can lead to gout and are associated with other medical conditions, including diabetes and the formation of ammonium acid urate kidney stones.
Kidney stone disease, also known as renal calculus disease, nephrolithiasis or urolithiasis, is a crystallopathy where a solid piece of material develops in the urinary tract. Renal calculi typically form in the kidney and leave the body in the urine stream. A small calculus may pass without causing symptoms. If a stone grows to more than 5 millimeters, it can cause blockage of the ureter, resulting in sharp and severe pain in the lower back that often radiates downward to the groin. A calculus may also result in blood in the urine, vomiting, or painful urination. About half of people who have had a renal calculus are likely to have another within ten years.
Rhabdomyolysis is a condition in which damaged skeletal muscle breaks down rapidly, often due to high intensity exercise over a short period. Symptoms may include muscle pains, weakness, vomiting, and confusion. There may be tea-colored urine or an irregular heartbeat. Some of the muscle breakdown products, such as the protein myoglobin, are harmful to the kidneys and can cause acute kidney injury.
Allopurinol is a medication used to decrease high blood uric acid levels. It is specifically used to prevent gout, prevent specific types of kidney stones and for the high uric acid levels that can occur with chemotherapy. It is taken orally or intravenously.
Hyperuricaemia or hyperuricemia is an abnormally high level of uric acid in the blood. In the pH conditions of body fluid, uric acid exists largely as urate, the ion form. Serum uric acid concentrations greater than 6 mg/dL for females, 7 mg/dL for males, and 5.5 mg/dL for youth are defined as hyperuricemia. The amount of urate in the body depends on the balance between the amount of purines eaten in food, the amount of urate synthesised within the body, and the amount of urate that is excreted in urine or through the gastrointestinal tract. Hyperuricemia may be the result of increased production of uric acid, decreased excretion of uric acid, or both increased production and reduced excretion.
Hypocalcemia is a medical condition characterized by low calcium levels in the blood serum. The normal range of blood calcium is typically between 2.1–2.6 mmol/L, while levels less than 2.1 mmol/L are defined as hypocalcemic. Mildly low levels that develop slowly often have no symptoms. Otherwise symptoms may include numbness, muscle spasms, seizures, confusion, or in extreme cases cardiac arrest.
Hypercalcemia, also spelled hypercalcaemia, is a high calcium (Ca2+) level in the blood serum. The normal range is 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L), with levels greater than 2.6 mmol/L defined as hypercalcemia. Those with a mild increase that has developed slowly typically have no symptoms. In those with greater levels or rapid onset, symptoms may include abdominal pain, bone pain, confusion, depression, weakness, kidney stones or an abnormal heart rhythm including cardiac arrest.
Hyperkalemia is an elevated level of potassium (K+) in the blood. Normal potassium levels are between 3.5 and 5.0 mmol/L (3.5 and 5.0 mEq/L) with levels above 5.5 mmol/L defined as hyperkalemia. Typically hyperkalemia does not cause symptoms. Occasionally when severe it can cause palpitations, muscle pain, muscle weakness, or numbness. Hyperkalemia can cause an abnormal heart rhythm which can result in cardiac arrest and death.
Electrolyte imbalance, or water-electrolyte imbalance, is an abnormality in the concentration of electrolytes in the body. Electrolytes play a vital role in maintaining homeostasis in the body. They help to regulate heart and neurological function, fluid balance, oxygen delivery, acid–base balance and much more. Electrolyte imbalances can develop by consuming too little or too much electrolyte as well as excreting too little or too much electrolyte. Examples of electrolytes include calcium, chloride, magnesium, phosphate, potassium, and sodium.
The enzyme urate oxidase (UO), uricase or factor-independent urate hydroxylase, absent in humans, catalyzes the oxidation of uric acid to 5-hydroxyisourate:
Rasburicase, sold under the brand name Elitek in the US and Fasturtec in the EU, is a medication that helps to clear uric acid from the blood. It is a recombinant version of urate oxidase, an enzyme that metabolizes uric acid to allantoin. Urate oxidase is known to be present in many mammals but does not naturally occur in humans. Rasburicase is produced by a genetically modified Saccharomyces cerevisiae strain. The complementary DNA (cDNA) coding for rasburicase was cloned from a strain of Aspergillus flavus.
Crush syndrome is a medical condition characterized by major shock and kidney failure after a crushing injury to skeletal muscle. Crush injury is compression of the arms, legs, or other parts of the body that causes muscle swelling and/or neurological disturbances in the affected areas of the body, while crush syndrome is a localized crush injury with systemic manifestations. Cases occur commonly in catastrophes such as earthquakes, to individuals that have been trapped under fallen or moving masonry.
Clofarabine is a purine nucleoside antimetabolite marketed in the United States and Canada as Clolar. In Europe and Australia/New Zealand the product is marketed under the name Evoltra. It is FDA-approved for treating relapsed or refractory acute lymphoblastic leukaemia (ALL) in children after at least two other types of treatment have failed. Some investigations of effectiveness in cases of acute myeloid leukaemia (AML) and juvenile myelomonocytic leukaemia (JMML) have been carried out. Ongoing trials are assessing its efficacy for managing other cancers.
Hypouricemia or hypouricaemia is a level of uric acid in blood serum that is below normal. In humans, the normal range of this blood component has a lower threshold set variously in the range of 2 mg/dL to 4 mg/dL, while the upper threshold is 530 μmol/L (6 mg/dL) for women and 619 μmol/L (7 mg/dL) for men. Hypouricemia usually is benign and sometimes is a sign of a medical condition.
Acute uric acid nephropathy is a rapidly worsening (decreasing) kidney function that is caused by high levels of uric acid in the urine (hyperuricosuria).
Calcium gluconate is the calcium salt of gluconic acid and is used as a mineral supplement and medication. As a medication it is used by injection into a vein to treat low blood calcium, high blood potassium, and magnesium toxicity. Supplementation is generally only required when there is not enough calcium in the diet. Supplementation may be done to treat or prevent osteoporosis or rickets. It can also be taken by mouth but is not recommended for injection into a muscle.
Nephrocalcinosis, once known as Albright's calcinosis after Fuller Albright, is a term originally used to describe the deposition of poorly soluble calcium salts in the renal parenchyma due to hyperparathyroidism. The term nephrocalcinosis is used to describe the deposition of both calcium oxalate and calcium phosphate. It may cause acute kidney injury. It is now more commonly used to describe diffuse, fine, renal parenchymal calcification in radiology. It is caused by multiple different conditions and is determined by progressive kidney dysfunction. These outlines eventually come together to form a dense mass. During its early stages, nephrocalcinosis is visible on x-ray, and appears as a fine granular mottling over the renal outlines. It is most commonly seen as an incidental finding with medullary sponge kidney on an abdominal x-ray. It may be severe enough to cause renal tubular acidosis or even end stage kidney disease, due to disruption of the kidney tissue by the deposited calcium salts.
Hyperuricosuria is a medical term referring to the presence of excessive amounts of uric acid in the urine. For men this is at a rate greater than 800 mg/day, and for women, 750 mg/day. Notable direct causes of hyperuricosuria are dissolution of uric acid crystals in the kidneys or urinary bladder, and hyperuricemia. Notable indirect causes include uricosuric drugs, rapid breakdown of bodily tissues containing large quantities of DNA and RNA, and a diet high in purine.
Potassium binders are medications that bind potassium ions in the gastrointestinal tract, thereby preventing its intestinal absorption. This category formerly consisted solely of polystyrene sulfonate, a polyanionic resin attached to a cation, administered either orally or by retention enema to patients who are at risk of developing hyperkalaemia. Newer drugs include: another polyanionic polymer, patiromer, which exchanges calcium for potassium; and Sodium zirconium cyclosilicate crystals, which exchange sodium for potassium
Leukostasis is a medical emergency most commonly seen in patients with acute myeloid leukemia. It is characterized by an extremely elevated blast cell count and symptoms of decreased tissue perfusion. The pathophysiology of leukostasis is not well understood, but inadequate delivery of oxygen to the body's cells is the result. Leukostasis is diagnosed when white cell plugs are seen in the microvasculature. The most common symptoms are dyspnea and hypoxia, usually accompanied by visual changes, headaches, dizziness, confusion, somnolence, and coma. Prompt treatment is required since, if left untreated, it has a very high mortality rate. Treatments aim to rapidly reduce white blood cell counts while also treating the underlying disorder.
... result in severe metabolic derangements (e.g., hyperuricemia, hypocalcemia, lactic acidosis, and the acute tumor lysis syndrome) which require expeditious management. Hyperuricemia Uric acid is the end product of purine catabolism.