The Food and Drug Administration has approved Elitek™ (rasburicase) for pediatric patients at a high risk of developing tumor lysis syndrome from treatment of their cancer.
Tumor lysis syndrome (TLS) can be a serious complication resulting from the treatment of cancer. Tumor lysis syndrome is most often caused by the sudden, rapid death of cells, particularly cancer cells, in response to cancer therapies. Tumor lysis syndrome may occur spontaneously, although the occurrence of this is rare. When the cells are killed by therapy, they may spill their inner (intracellular) contents, which accumulate in the body faster than can be eliminated. The contents can cause metabolic and electrolyte disturbances that can progress to life-threatening complications if not diagnosed and treated appropriately. Tumor lysis syndrome occurs most frequently in patients with acute hematologic (blood) cancers, such as leukemias or lymphomas, that respond very rapidly to chemotherapy.
Some patients feel no symptoms of tumor lysis syndrome in its early stages, but have abnormal laboratory results indicative of its progression. Laboratory results will show high uric acid, potassium, and phosphorous levels and low calcium levels in the blood. Some patients with tumor lysis syndrome may have initial symptoms including nausea and vomiting, shortness of breath and lethargy, irregular heartbeat and cardiac dysfunction, clouding of urine, impairment and loss of consciousness and/or joint discomfort. If tumor lysis syndrome is left untreated, its progression may cause acute kidney failure, cardiac arrhythmias, seizures, loss of muscle control and death. However, tumor lysis syndrome is a preventable and treatable condition, particularly in its early stages.
High uric acid levels caused by tumor lysis syndrome can result in the formation of crystals that lodge in the small tubes of the kidneys and can cause acute kidney (renal) failure – a condition that can be life threatening. Elitek™ is a genetically engineered enzyme (protein) that breaks down uric acid so that the body can safely excrete the by-products through the urine.
Historically, the agent allopurinol was the standard treatment utilized for patients with high uric acid levels and/or tumor lysis syndrome. Recently, a clinical trial was conducted to compare Elitek™ to allopurinol in children with lymphoma or leukemia who were at a high risk for developing TLS. Uric acid levels in the blood were significantly lower in patients treated with Elitek™ than in patients treated with allopurinol. Four hours after treatment, uric acid levels were decreased by 86% in patients treated with Elitek™, compared to only 12% in patients treated with allopurinol. Furthermore, levels of the metabolic compound creatinine, indicating kidney malfunction, improved during the 4 days of treatment with Elitek™ and actually worsened during treatment with allopurinol.
Parents of children who are being treated for cancer may wish to speak with their child’s physician about the risk of tumor lysis syndrome and the risks and benefits of treatment with Elitek™ if their child is at a high risk for developing the syndrome.
Reference: Sanofi-Synthelabo. Elitek™ (rasburicase) has been approved by the FDA in the United States. Available at: http://www.prnewswire.com/cgi-bin/stories.pl?ACCT=105&STORY=/www/story/07-16-2002/0001765208. Accessed July 17, 2002.
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