Tumor lysis syndrome refers to the constellation of metabolic disturbances that occurs when large numbers of neoplastic cells die rapidly, leading to the release of intracellular ions and metabolic byproducts into the systemic circulation.[1] Clinically, the syndrome is characterized by rapid development of hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and acute kidney injury.[2, 3] (See Pathophysiology, Etiology, Presentation, and Workup.)
Tumor lysis syndrome arises most commonly after the start of initial chemotherapeutic treatment, but spontaneous cases have increasingly been documented.[4, 5]
Although tumor lysis syndrome has been reported with virtually every type of tumor, it is typically associated with bulky, rapidly proliferating, treatment-responsive tumors—typically, acute leukemias and high-grade non-Hodgkin lymphomas such as Burkitt lymphoma.[6, 7] The syndrome has also been reported with other hematologic malignancies and with solid tumors such as hepatocellular carcinoma, lung cancer, and melanoma, especially when metastatic.[8]
Because tumor lysis syndrome is potentially lethal, the main principles of management are (1) identification of high-risk patients with initiation of preventive therapy and (2) early recognition of metabolic and renal complications and the prompt administration of supportive care. Hydration and control of serum uric acid are central to both prevention and treatment. Management of hyperkalemia, hypocalcemia, and hyperphosphatemia is also critical.[9, 10, 11] Indications for dialysis include persistent hyperkalemia or hyperphosphatemia, volume overload, uremia, symptomatic hypocalcemia, and hyperuricemia. (See Treatment, and Medication.)
Rapid tumor cell turnover results in release of intracellular contents into the circulation. This release can inundate renal elimination and cellular buffering mechanisms, leading to numerous metabolic derangements.
Clinically significant tumor lysis syndrome can occur spontaneously, but it is most often seen 48-72 hours after initiation of cancer treatment. Hyperkalemia is often the earliest laboratory manifestation. Hyperkalemia and hyperphosphatemia result directly from rapid cell lysis.
Hypocalcemia is a consequence of acute hyperphosphatemia with subsequent precipitation of calcium phosphate in soft tissues. In acute kidney injury, decreased calcitriol levels also cause hypocalcemia.
Uric acid is the terminal catabolic product of purine metabolism in humans. Nucleic acid purines, which are released by cell breakdown, are ultimately metabolized to uric acid by hepatic xanthine oxidase. This conversion leads to hyperuricemia.
Uric acid is a weak acid with a pKa of approximately 5.4. It is soluble in plasma and is freely filtered at the renal glomeruli. However, uric acid is less soluble in renal tubular and collecting duct fluid due to normally acidic media, thus increasing the possibility of uric acid crystal formation in cases of hyperuricemia.
The kidney is the primary organ involved in the clearance of uric acid, potassium, and phosphate. Preexisting volume depletion or kidney dysfunction predisposes patients to worsening metabolic derangements and acute kidney injury (AKI). The AKI is often oliguric and can be multifactorial in etiology.
Uric acid nephropathy, however, is the major cause of AKI. Its development is due to mechanical obstruction by uric acid crystals in the renal tubules. Uric acid has a pKa of 5.6; uric acid precipitation is enhanced by high acidity and high concentration in the renal tubular fluid, and uric acid becomes less soluble as renal tubule pH decreases. Renal medullary hemoconcentration and decreased tubular flow rate also contribute to crystallization.[12]
Another cause of AKI is acute nephrocalcinosis from calcium phosphate crystal precipitation, which may also occur in other tissues. This develops in the setting of hyperphosphatemia and is exacerbated by overzealous iatrogenic alkalinization, because calcium phosphate, unlike uric acid, becomes less soluble at an alkaline pH. Precipitation of xanthine, which is even less soluble in urine than uric acid and whose urinary excretion is increased by the use of xanthine oxidase inhibitors such as allopurinol, is another cause of AKI.[13, 14]
Tumor lysis syndrome occurs most often in patients with acute leukemia with high white blood cell (WBC) counts and in those with high-grade lymphomas, in response to aggressive treatment. Tumor lysis syndrome may also occur in other hematologic malignancies and in a variety of solid tumors such as hepatocellular carcinoma, lung cancer, and melanoma (especially when metastatic); neuroblastoma; and germ cell tumors.[7, 8] It occasionally occurs spontaneously, prior to any form of therapy.[1, 5]
Patients at highest risk are those with bulky, rapidly proliferating tumors that are sensitive to treatment. An elevated pretreatment lactate dehydrogenase (LDH) level, which correlates with high tumor volume, is a strong prognostic indicator for developing clinically significant complications of therapy. The presence of kidney insufficiency prior to therapy also correlates with an increased likelihood of tumor lysis syndrome.
An international consensus expert panel has proposed a classification that stratifies cancers into high, intermediate, or low risk for tumor lysis syndrome.[7] The high-risk group of cancers includes the following:
Intermediate-risk malignancies include the following:
Low-risk diseases include the following:
Reports exist of tumor lysis syndrome associated with the administration of radiation therapy,[15] corticosteroids, hormonal agents, biologic response modifiers, and monoclonal antibodies.[10] Agents reported to cause tumor lysis syndrome include the following:
The development of tumor lysis syndrome is not limited to the systemic administration of agents; it can occur with intrathecal administration of chemotherapy and with chemo-embolization.[22]
Rare clinical situations in which tumor lysis syndrome has been observed include pregnancy and fever. Patients under general anesthesia have also experienced tumor lysis syndrome.
The incidence of tumor lysis syndrome is unknown. The rate varies among different malignancies; bulky, aggressive, treatment-sensitive tumors are associated with higher frequencies of tumor lysis syndrome. In a study of frequency in patients with high-grade non-Hodgkin lymphoma, laboratory evidence of tumor lysis syndrome occurred much more frequently than the symptomatic clinical syndrome (42% versus 6% of cases, respectively). In a study of children with acute leukemia receiving induction chemotherapy, laboratory evidence of tumor lysis syndrome was found in 70% of cases but clinically significant tumor lysis syndrome occurred in only 3%.[23]
As advances are made in cancer treatment and as high-dose regimens become more commonplace, tumor lysis syndrome incidence may increase and the syndrome may emerge in a broader spectrum of malignancies.
Although tumor lysis syndrome occurs in all age groups, advanced age leading to impaired kidney function may predispose patients to clinically significant tumor lysis syndrome, owing to a decreased ability to dispose of tumor lysis byproducts.
Early recognition of signs and symptoms of patients at risk for tumor lysis syndrome, including identification of abnormal clinical and laboratory values, can lead to successful prevention of the otherwise life-threatening complications of the condition.
Potential complications of tumor lysis syndrome include uremia and oliguric acute kidney injury due to tubule precipitation of uric acid, calcium phosphate, or xanthine or hypoxanthine
Severe electrolyte disturbances, such as hyperkalemia and hypocalcemia, predispose patients to cardiac arrhythmias and seizures.
Iatrogenic complications, such as pulmonary edema from overly vigorous hydration or metabolic alkalosis from excess administration of bicarbonate, can also occur and are life-threatening if not immediately addressed.
Renal tubule precipitation of uric acid, calcium phosphate, or xanthine or hypoxanthine causes acute kidney injury. This is often oliguric (< 400 mL daily) in nature, leading to volume overload and complications of hypertension and pulmonary edema.
High blood urea nitrogen (BUN) levels due to increased protein catabolism and acute kidney injury can be severe enough to result in pericarditis, platelet dysfunction, and defective cellular immunity. Kidney dysfunction can be severe enough to require dialysis, but with prompt supportive measures, it is usually reversible.
Hyperkalemia can lead to electrocardiographic changes and life-threatening cardiac arrhythmia, including asystole. Severe potassium elevation can cause electrocardiographic alterations such as peaked T waves, flattened P waves, prolonged PR interval, widened QRS complexes, deep S wave, and sine waves. Hypocalcemia can lead to QT interval lengthening, which predisposes to ventricular arrhythmia.
Acute kidney injury and the liberation of large amounts of endogenous intracellular acids from cellular catabolism result in acidemia. This acidemia causes a decrease in serum bicarbonate concentration and a high anion gap acidosis (see the Anion Gap calculator).
Acidemic states can worsen the many electrolyte imbalances already present in tumor lysis syndrome; intracellular uptake of potassium is hindered, uric acid solubility is decreased, and extracellular shift of phosphate is promoted. Calcium phosphate solubility, however, improves in acidic conditions.
The myriad of metabolic disorders must be assessed and treated rapidly. Proper fluid management, alkalinization of the urine, correction of acidosis, and attention to infections are the mainstays of therapy.
In tumor lysis syndrome, a constellation of clinical signs and symptoms may develop prior to the initiation of chemotherapy or, more commonly, within 72 hours after administration of cytotoxic therapy.[24] Inquiries should be made with regard to the following:
Other manifestations of tumor lysis syndrome include the following:
Clinical manifestations reflect the severity of underlying metabolic abnormalities. Hyperkalemia can cause paresthesia, weakness, and fatal cardiac arrhythmias.
Severe hypocalcemia can lead to the following signs and symptoms:
Deposition of calcium phosphate in various tissues may be responsible for the following signs and symptoms:
Uremia can produce the following signs and symptoms:
As uremia progresses, paresthesia and evidence of pericarditis may develop, as well as signs of drug toxicity from medications eliminated by the kidney. Features of volume overload, such as dyspnea, pulmonary rales, edema, and hypertension, may develop.
Elevated uric acid levels may produce lethargy, nausea, and vomiting. Rapidly increasing uric acid levels may lead to arthralgia and renal colic.
Before beginning treatment for cancer, clinicians should determine the patient's risk for tumor lysis syndrome by assessing tumor burden, histopathologic findings, and kidney function (see Overview/Etiology.) Early recognition of signs and symptoms of patients at risk for tumor lysis syndrome, including identification of abnormal clinical and laboratory values, can lead to successful prevention of the otherwise life-threatening complications of this condition.
In patients with tumor lysis syndrome, blood samples obtained by a wide-bore needle or, preferably, an indwelling cannula should be used to obtain a biochemical profile of the patient for monitoring, including of serum sodium, potassium, chloride, and bicarbonate.
If hyperuricemia develops, urine alkalinization prevents renal precipitation of uric acid but may increase the risk for nephrocalcinosis. If alkaline diuresis is employed, regular determinations of urine pH should guide the extent of therapy.
Because increased urine flow rates help to inhibit crystal deposition in renal tubules, close monitoring of urine output is necessary to assess adequacy of hydration. Monitoring urine output for signs of oliguric acute kidney injury is also necessary.
Radiography of the chest is useful to determine the presence of a large tumor (eg, mediastinal mass). Perform ultrasonography or computed tomography (CT) scanning of the abdomen and retroperitoneum immediately if acute kidney injury or mass lesions in the abdomen are present. Intravenous (IV) contrast medium may be contraindicated in a patient with kidney insufficiency.
Frequent cardiac assessment (electrocardiography [ECG] or continuous cardiac monitoring) is necessary to monitor ECG changes, which may herald a lethal arrhythmia caused by potassium and calcium disturbances.
Pathologic studies demonstrate deposits of uric acid within the distal renal tubule lumina, which cause intrarenal hydronephrosis. Uric acid crystals can also be seen within tubular epithelial cells and the medullary microcirculation. Uric acid precipitates may also occur in the renal pelvis and ureters, leading to hydronephrosis and acute kidney injury from extrarenal sources.
High-risk patients should have laboratory monitoring (BUN, creatinine, phosphate, uric acid, and calcium levels) prior to therapy and for 48-72 hours after treatment induction. Follow measurements at least three times per day, or more often if evidence of tumor lysis syndrome develops. Lactate dehydrogenase (LDH) should be checked at least on diagnosis and prior to treatment, as elevated values can reflect the potential for progressing to tumor lysis syndrome with the initiation of chemotherapy.
Most patients with tumor lysis syndrome have laboratory derangements in LDH, potassium, phosphate, calcium, and uric acid, as well as abnormal kidney function study results, occurring 1-3 days after chemotherapy initiation. Hyperkalemia is often the first life-threatening abnormality.
Appropriate management of tumor lysis syndrome requires preventive measures in high-risk patients prior to cancer treatment, as well as the prompt initiation of supportive care for patients who develop acute tumor lysis syndrome during treatment.[26, 27, 28] Conservative management and prevention of tumor lysis syndrome are similar, focusing on hydration and control of serum uric acid. Management of hyperkalemia, hypocalcemia, and hyperphosphatemia is also critical.[9, 10, 11] Diuresis or urinary alkalinization may be considered in select cases but are potentially hazardous.
Patients with evidence of pretreatment (spontaneous) acute tumor lysis syndrome should be started immediately on therapy for it. If possible, cancer treatment should be withheld until all parameters are corrected.
Cancer patients with acute manifestations of tumor lysis syndrome or those at high risk should be treated by personnel who are experienced with the condition’s complications and treatment. An oncology unit or intensive care unit (ICU) with readily available, continuous cardiac monitoring and hemodialysis capabilities is the preferred treatment setting.[29]
If basic supportive care measures are ineffective in controlling electrolyte disturbances or acute kidney injury, nephrology and critical care consultants should be accessible to assist in further management. Indications for dialysis include persistent hyperkalemia or hyperphosphatemia, volume overload, uremia, symptomatic hypocalcemia, and hyperuricemia. Surgical intervention for central venous line placement or for the placement of a dialysis catheter may be necessary.
Laboratory turnover time must be rapid so that metabolic derangements can be addressed before life-threatening problems arise.
Severe manifestations of tumor lysis syndrome can be prevented only through meticulous laboratory monitoring and careful clinical observation. Necessary cardiac studies include a baseline electrocardiogram with follow-up studies or continuous cardiac monitoring during treatment. Appropriate kidney function surveillance and fluid status determinations require baseline and daily weights, regular vital sign checks, and frequent measurements of both fluid intake and urine output.
Patients at high risk and those with evidence of tumor lysis syndrome should have the following levels monitored at least three times daily:
Monitoring should continue for the first 48-72 hours after chemotherapy initiation. Some patients may need to be placed on dialysis prior to the initiation of therapy.
Volume depletion is a major risk factor for tumor lysis syndrome and must be corrected vigorously. Aggressive IV hydration not only helps to correct electrolyte disturbances by diluting extracellular fluid, it also increases intravascular volume. Increased volume enhances renal blood flow, glomerular filtration rate, and urine volume, thus decreasing the concentration of solutes in the distal nephron and medullary microcirculation.
In patients at low risk, preventive hydration can be done on an outpatient basis. These patients should increase their fluid intake to 2–3 L/m2 daily, starting before cancer therapy that poses a risk of tumor lysis syndrome and continuing until the end of the day after chemotherapy.[11]
In patients at intermediate or high risk, preventive hydration should be with continuous IV infusion of 2–3 L/m2 daily, beginning 24-48 hours prior to initiation of cancer therapy and continuing for 48-72 hours afterward. These infusion rates should yield urine volumes of 80–100 mL/m2/h (at least 3 L daily). Patients must be monitored for volume overload.
For patients who develop tumor lysis syndrome, expert consensus guidelines recommend the following for hydration[11] :
The use of furosemide or mannitol for osmotic diuresis has not proven to be beneficial as front-line therapy. In fact, these modalities may contribute to uric acid or calcium phosphate precipitation in renal tubules in a volume-contracted patient.
Diuretics should be reserved for well-hydrated patients with insufficient diuresis, and furosemide alone should be considered for the normovolemic patient with hyperkalemia or for the patient with evidence of fluid overload.
Intravenous infusion of isotonic sodium bicarbonate solutions to promote alkaline diuresis has the potential benefit of solubilizing, and thus minimizing, intratubular precipitation of uric acid. The goal is to increase urinary pH to 7.0 to maximize uric acid solubility in renal tubules and vessels.
Drawbacks to systemic alkaline therapy include magnification of clinical hypocalcemia by shifting ionized calcium to its nonionized form. An increased likelihood of calcium phosphate precipitation in renal tubules is an additional drawback. For those reasons, routine urine alkalinization is controversial, and if it is employed, it must include close monitoring of urinary pH, serum bicarbonate, and uric acid levels to guide therapy and avoid overzealous alkalinization. Consider withdrawing sodium bicarbonate from IV fluid solutions once serum bicarbonate levels reach 30 mEq/L, urinary pH exceeds 7.5, or serum uric acid levels have normalized.
If urinary alkalinization is not achieved with exogenous bicarbonate solutions despite increasing serum bicarbonate levels, IV acetazolamide at doses of 250-500 mg daily (5 mg/kg daily) may be added to decrease proximal tubule bicarbonate reabsorption, thereby increasing urinary pH.
Measures for management of hyperuricemia in tumor lysis syndrome include the following:
Allopurinol is a xanthine oxidase inhibitor; it is administered to reduce the conversion of nucleic acid byproducts to uric acid in order to prevent urate nephropathy and subsequent oliguric acute kidney injury.[1] It is usually given orally at 600 mg daily for prophylaxis and 600-900 mg daily (up to a maximum of 500 mg/m2 daily) for treatment of tumor lysis syndrome. Patients unable to take oral medications can be given IV allopurinol.
Adverse effects include mild-to-severe rash, xanthine stone–induced urolithiasis, acute interstitial nephritis, pneumopathy, fever, and eosinophilia. Moreover, the inhibition of uric acid synthesis promotes an increase of xanthine in plasma and the renal system; although reported to be rare, xanthine has the capacity to precipitate in the renal tubules.
Dose reduction is necessary in kidney insufficiency or if the medication is given concomitantly with mercaptopurine, 6-thioguanine, or azathioprine (since allopurinol interferes with the metabolism of these agents).
Rasburicase (recombinant urate oxidase) can be used when uric acid levels cannot be lowered sufficiently by standard approaches.[30] Humans do not express urate oxidase, which catalyses the conversion of poorly soluble uric acid to soluble allantoin. By converting uric acid to water-soluble metabolites, urate oxidase effectively decreases plasma and urinary uric acid levels. Rasburicase is approved by the US Food and Drug Administration (FDA) for the initial management of plasma uric acid levels in pediatric and adult patients with leukemia, lymphoma, and solid tumor malignancies who are receiving anticancer therapy expected to result in tumor lysis and hyperuricemia.[31]
Rasburicase has a more rapid onset of action than allopurinol. Unlike allopurinol, uricase does not increase excretion of xanthine and other purine metabolites; therefore, it does not increase tubule crystallization of these compounds. Rasburicase has become the standard choice for prevention and treatment of hyperuricemia in high-risk patients, especially children.[9, 10, 23]
Rasburicase is administered by IV infusion. The standard dosage is 0.2 mg/kg per day for 5 days, but studies have reported success with a single dose of rasburicase—weight based; or 3, 6, or 7.5 mg in adults.[32, 33, 34] Guidelines from the National Comprehensive Cancer Network and the British Committee for Standards in Haematology agree that a single dose will suffice in most patients, although careful followup is necessary.[9, 10]
Rasburicase is contraindicated in glucose-6-phosphate dehydrogenase (G6PD) deficiency and pregnancy. In G6PD deficiency, excess hydrogen peroxide accumulates as rasburicase breaks down uric acid and accelerates catabolism of its precursors xanthine and hypoxanthine; this accumulation places patients at risk for hemolytic anemia and methemoglobinemia. Patients at higher risk (eg, those of African or Mediterranean ancestry) should be screened for G6PD deficiency prior to starting rasburicase. In addition, because humans do not express urate oxidase, rasburicase can potentially elicit an immune response.[31]
Febuxostat (Uloric) is a novel xanthine oxidase inhibitor that does not appear to have the hypersensitivity profile of allopurinol. In addition, this agent does not require dosing modification for kidney impairment.[4] Initial studies suggested that febuxostat is effective and safe for preventing tumor lysis syndrome.[35]
The Febuxostat for Tumor Lysis Syndrome Prevention in Hematologic Malignancies (FLORENCE) trial found that febuxostat provided better control of serum uric acid compared with allopurinol, with comparable preservation of kidney function and safety profile. In FLORENCE, 346 patients with hematologic malignancies at intermediate to high risk for tumor lysis syndrome were randomized to receive 120 mg of febuxostat or 200-600 mg of allopurinol daily, starting 2 days before induction chemotherapy, for 7-9 days. Mean area under curve for serum uric acid was was 514.0 ± 225.71 mg h/dL for febuxostat versus 708.0 ± 234.42 mg h/dL for allopurinol (P< 0.0001).[36]
In a Japanese phase III trial comparing febuxostat with allopurinol for prevention of thyperuricemia in 100 patients with malignant tumors receiving chemotherapy, febuxostat was non-inferior to allopurinol. No differences in safety outcomes with either medication was noted.[37]
Febuxostat is much more expensive than allopurinol. However, in patients with kidney impairment or hypersensitivity to allopurinol, febuxostat may be a reasonable choice for prophylaxis of tumor lysis syndrome, pending the publication of further clinical trial results.[4, 38]
Ito et al point out that inhibition of xanthine oxidase by febuxostat can cause accumulation of xanthine and urinary excretion of xanthine crystals. They report three cases in which xanthine crystals appeared in the urine of patients with hematologic malignancies who received febuxostat for prophylaxis during tumor lysis syndrome; the crystals were noted when yellowish and pinkish deposits were observed in urinary tract catheters and urine bags. The authors recommend careful observation and management to avoid xanthine nephropathy in this setting.[14]
Aggressively treat and monitor hyperkalemia. Immediately restrict dietary potassium and remove potassium from IV fluids. Acute treatment modalities include IV infusion of glucose plus insulin to promote redistribution of potassium from the extracellular to the intracellular space, and IV calcium gluconate as cardioprotection for potassium levels greater than 6.5 mmol/L or for patients with electrocardiographic alterations.
IV hydration with alkaline fluid can also increase intracellular uptake of potassium. Potassium-wasting diuretics may be employed with caution since these may worsen renal precipitation in the volume-contracted patient. Long-term therapy, such as oral potassium exchange resins, should be given immediately because of the transient effectiveness of acute treatment modalities. If these measures fail to control serum potassium, dialysis should be initiated promptly.
Hyperphosphatemia is managed with oral phosphate binders and the same solution of glucose plus insulin used for the control of hyperkalemia. The phosphate binder sevelamer, which is approved for controlling serum phosphorus in patients with chronic kidney disease who are on dialysis, has been used successfully to control hyperphosphatemia in children with tumor lysis syndrome.[39] Significant hyperphosphatemia may be difficult to control other than with dialysis.[10]
Hyperphosphatemia may lead to hypocalcemia, which usually resolves as phosphate levels are corrected. In some cases, depressed serum 1,25-dihydroxycholecalciferol levels contribute to hypocalcemia, and administration of calcitriol may correct calcium levels. Such therapy, however, should not be undertaken until serum phosphate levels have normalized, to avoid metastatic calcium phosphate calcifications. As a rule, do not correct hypocalcemia unless evidence of neuromuscular irritability exists, as indicated by a positive Chvostek or Trousseau sign.
If the previously described therapies for the complications of tumor lysis syndrome fail, consider early initiation of dialysis. Dialysis prevents irreversible kidney failure and other life-threatening complications. Indications for dialysis include persistent hyperkalemia or hyperphosphatemia despite treatment, volume overload, uremia, symptomatic hypocalcemia, and hyperuricemia.
Hemodialysis is preferred over peritoneal dialysis because of better phosphate and uric acid clearance rates. Continuous hemofiltration also has been used and is effective in correcting electrolyte abnormalities and fluid overload.
Because hyperkalemia can recur after dialysis is initiated and because of the high phosphate burden in some patients with tumor lysis syndrome, electrolyte levels must be monitored frequently and dialysis repeated as needed.
Dietary restrictions are highly dependent on the status of the individual patient. However, patients who are not restricted to a nothing-by-mouth diet could theoretically benefit from restriction of intake of foods that contain high levels of potassium, phosphorus, or uric acid.
The National Comprehensive Cancer Network advises that tumor lysis syndrome is best managed if it is anticipated and treatment is started before initiation of chemotherapy. High-risk features for tumor lysis syndrome include the following[9] :
Treatment of tumor lysis syndrome centers on the following[9] :
The NCCN recommends allopurinol for first-line treatment and retreatment for hyperuricemia. Allopurinol is begun 2–3 days prior to chemotherapy and continued for 10–14 days. Febuxostat may be used in patients intolerant to allopurinol.
Alternatively, the NCCN recommends rasburicase when allopurinol is ineffective, and for patients with any of the following risk factors:
The NCCN notes that a single dose of 3–6 mg of rasburicase is frequently adequate. Redosing should be individualized.[9]
Guidelines from the British Committee for Standards in Haematology (BCSH) include the following recommendations for prevention of tumor lysis syndrome[10] :
BCSH recommendations on the use of rasburicase for prevention are as follows[10] :
Expert consensus guidelines for the prophylaxis and management of tumor lysis syndrome in the United States provide a decision tree for classifying patients with cancer as being at low, intermediate, or high risk. Risk factors include patient features (eg, older age, impaired kidney function), malignancy type and grade, and chemotherapy agent selected (eg, high concern with venetoclax). The guidelines also provide detailed schedules for inpatient and outpatient monitoring and prophylaxis, including hydration and laboratory testing, and specific recommendations for hyperkalemia, hyperphosphatemia, hypocalcemia, and hyperuricemia.[11]
The management of tumor lysis syndrome, other than hydration and possibly alkalinization, necessitates the administration of drugs to correct metabolic disturbances. Use of these medications should be instituted before the start of chemotherapy; the goal is to achieve optimal metabolic stability. Medications can be adjusted after the start of chemotherapy in response to the level of tumor lysis and/or metabolic disturbances.
Allopurinol, a xanthine oxidase inhibitor, reduces the conversion of nucleic acid byproducts to uric acid, in this way preventing urate nephropathy and subsequent oliguric acute kidney injury.[1] Alternatives to allopurinol for decreasing uric acid load are the xanthine oxidase inhibitors rasburicase (urate oxidase) and febuxostat.[30, 36]
Clinical Context: Allopurinol inhibits xanthine oxidase, the enzyme that synthesizes uric acid from hypoxanthine and xanthine, thus decreasing production and excretion of uric acid and increasing the levels of more soluble xanthine and hypoxanthine. The drug reduces the synthesis of uric acid without disrupting the biosynthesis of vital purines. Patient response is measured by serum uric acid levels assessed at 48 hours after the initiation of therapy. Dosage adjustments are made as needed.
Clinical Context: Rasburicase is a recombinant form of the enzyme urate oxidase, which oxidizes uric acid to allantoin. It is indicated for the treatment and prophylaxis of severe hyperuricemia associated with the treatment of malignancy. Hyperuricemia causes a precipitant in the kidneys, which leads to acute renal failure. Unlike uric acid, allantoin is soluble and easily excreted by the kidneys. Elimination half-life for rasburicase is 18 hours.
Clinical Context: Xanthine oxidase inhibitor; inhibits conversion of hypoxanthine to xanthine to uric acid; at therapeutic dosages, decreases production of uric acid without disrupting synthesis of vital purines and pyrimidines
These agents control hyperuricemia and are used to attempt to prevent urate nephropathy and subsequent oliguric acute kidney injury.
Allopurinol inhibits xanthine oxidase, thereby reducing uric acid. The IV form (Aloprim) may be used for patients unable to tolerate oral administration.
Caution is necessary because of the high uric acid concentration in the urine. Andreoli and associates explained some cases of renal failure on the basis of effects of allopurinol in altering purine excretion.[13] In the presence of allopurinol, the excretion of uric acid, xanthine, and hypoxanthine increases several hundred fold, enough to exceed their solubility limit in the renal tubules even at a urinary pH level of 7. Also, at a urinary pH level higher than 7.5, crystallization of hypoxanthine may occur, which necessitates withdrawal of bicarbonate from IV fluids.
Clinical Context: Insulin promotes the redistribution of potassium from extracellular to intracellular space. It stimulates the cellular uptake of potassium within 20-30 minutes. Glucose should be administered along with insulin to prevent hypoglycemia. Monitor blood sugar levels frequently.
These agents are used to prevent and treat hyperkalemia and restore electrolyte balance.
Clinical Context: Furosemide increases the excretion of water by interfering with the chloride-binding cotransport system. This, in turn, inhibits sodium and chloride reabsorption in the ascending loop of Henle and the distal renal tubule. Furosemide has not proven to be beneficial as front-line therapy in tumor lysis syndrome. It may contribute to uric acid or calcium phosphate precipitation in renal tubules in volume-contracted patients.
These agents should be reserved for well-hydrated patients with insufficient diuresis.
Clinical Context: Acetazolamide is a carbonic anhydrase inhibitor. It may be added to decrease proximal tubule bicarbonate reabsorption, thereby increasing urinary pH.
Clinical Context: Sodium bicarbonate is used intravenously to alkalinize urine. It promotes alkaline diuresis, with the potential benefits of solubilizing, and thus minimizing, intratubular precipitation of uric acid. The goal is to increase urinary pH to 7 to maximize uric acid solubility in renal tubules and vessels.
Routine urine alkalinization is controversial, and if employed, it must include close monitoring of urinary pH, serum bicarbonate, and uric acid levels. Consider withdrawing sodium bicarbonate from IV solutions once serum bicarbonate levels reach 30 mEq/L, urinary pH is greater than 7.5, or serum uric acid levels have normalized.
Intracellularly, sodium bicarbonate shifts potassium. It may be considered in the treatment of hyperkalemia, even in the absence of metabolic acidosis.
Clinical Context: Calcium gluconate is used for cardioprotection when potassium levels are greater than 6.5 mmol/L or for patients with electrocardiographic alterations. This agent moderates nerve and muscle performance and facilitates normal cardiac function.
Clinical Context: Administer IV calcium gluconate or calcium chloride to stabilize myocardial conduction in a patient with cardiac arrhythmias. Calcium also moderates nerve and muscle performance by regulating the action potential excitation threshold. IV calcium is indicated in all cases of severe hyperkalemia (ie, >6 mEq/L), especially when accompanied by electrocardiographic changes.
Calcium chloride contains about 3 times more elemental calcium than an equal volume of calcium gluconate. Therefore, when hyperkalemia is accompanied by hemodynamic compromise, calcium chloride is preferred over calcium gluconate.
The administration of calcium should be accompanied by the use of other therapies that actually help to lower the serum levels of potassium.
Other calcium salts (eg, glubionate, gluceptate) have even less elemental calcium than calcium gluconate and are not generally recommended for the treatment of hyperkalemia.
Calcium is used to treat arrhythmias due to hyperkalemia or hypocalcemia. Frank or impending renal failure requires additional therapeutic measures. Hyperkalemia is the most common life-threatening emergency. Chemotherapy may have to be discontinued temporarily. The entire potassium intake should be immediately discontinued.
The use of calcium does not lower serum potassium levels. It is primarily used to protect the myocardium from the deleterious effects of hyperkalemia (ie, arrhythmias) by antagonizing the membrane actions of potassium.
Clinical Context: Sodium polystyrene sulfonate is used in the second stage of therapy to reduce total-body potassium. This agent exchanges sodium for potassium and binds it in the gut, primarily in the large intestine. Its onset of action after oral administration is 2-12 hours and is longer when administered rectally.
Clinical Context: Aluminum hydroxide has been shown to be an effective phosphate binder. Because of their potential for toxicity, however, aluminum salts are not used as first-line therapy.
Clinical Context: This is a polymeric phosphate binder for oral administration. It does not contain aluminum; thus, aluminum intoxication is not a concern.
Sodium polystyrene sulfonate is an exchange resin that can be used to treat mild to moderate hyperkalemia. Each milliequivalent of potassium is exchanged for 1 mEq of sodium. Agents to treat hyperphosphatemia are also used.