• Daniel Kl Cheuk, Alan Ks Chiang, Godfrey Cf Chan, and Shau Yin Ha.
• Department of Pediatrics and Adolescent Medicine, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Hong Kong, China.
• Cochrane Db Syst Rev. 2017 Mar 8; 3 (3): CD006945CD006945.

BackgroundTumour lysis syndrome (TLS) is a serious complication of malignancies and can result in renal failure or death. Previous reviews did not find clear evidence of benefit of urate oxidase in children with cancer. This review is the second update of a previously published Cochrane review.ObjectivesTo assess the effects and safety of urate oxidase for the prevention and treatment of TLS in children with malignancies.Search MethodsIn March 2016 we searched CENTRAL, MEDLINE, Embase, and CINAHL. In addition, we searched the reference lists of all identified relevant papers, trials registers and other databases. We also screened conference proceedings and we contacted experts in the field and the manufacturer of rasburicase, Sanofi-aventis.Selection CriteriaRandomised controlled trials (RCT) and controlled clinical trials (CCT) of urate oxidase for the prevention or treatment of TLS in children under 18 years with any malignancy.Data Collection And AnalysisTwo review authors independently extracted trial data and assessed individual trial quality. We used risk ratios (RR) for dichotomous data and mean difference (MD) for continuous data.Main ResultsWe included seven trials, involving 471 participants in the treatment groups and 603 participants in the control groups. No new studies were identified in the update. One RCT and five CCTs compared urate oxidase and allopurinol. Three trials tested Uricozyme, and three trials tested rasburicase for the prevention of TLS.The RCT did not evaluate the primary outcome (incidence of clinical TLS). It showed no clear evidence of a difference in mortality (both all-cause mortality (Fisher's exact test P = 0.23) and mortality due to TLS (no deaths in either group)), renal failure (Fisher's exact test P = 0.46), and adverse effects between the treatment and the control groups (Fisher's exact test P = 1.0). The frequency of normalisation of uric acid at four hours (10 out of 10 participants in the treatment group versus zero out of nine participants in the control group, Fisher's exact test P < 0.001) and area under the curve of uric acid at four days (MD -201.00 mg/dLhr, 95% CI -258.05 mg/dLhr to -143.95 mg/dLhr; P < 0.00001) were significantly better in the treatment group.One CCT evaluated the primary outcome; no clear evidence of a difference was identified between the treatment and the control groups (RR 0.77, 95% CI 0.44 to 1.33; P = 0.34). Pooled results of three CCTs showed significantly lower mortality due to TLS in the treatment group (RR 0.05, 95% CI 0.00 to 0.89; P = 0.04); no clear evidence of a difference in all-cause mortality was identified between the groups (RR 0.19, 95% CI 0.01 to 3.42; P = 0.26). Pooled results from five CCTs showed significantly lower incidence of renal failure in the treatment group (RR 0.26, 95% CI 0.08 to 0.89; P = 0.03). Results of CCTs also showed significantly lower uric acid in the treatment group at two days (three CCTs: MD -3.80 mg/dL, 95% CI -7.37 mg/dL to -0.24 mg/dL; P = 0.04), three days (two CCTs: MD -3.13 mg/dL, 95% CI -6.12 mg/dL to -0.14 mg/dL; P = 0.04), four days (two CCTs: MD -4.60 mg/dL, 95% CI -6.39 mg/dL to -2.81 mg/dL; P < 0.00001), and seven days (one CCT: MD -1.74 mg/dL, 95% CI -3.01 mg/dL to -0.47 mg/dL; P = 0.007) after therapy, but not one day (three CCTs: MD -3.00 mg/dL, 95% CI -7.61 mg/dL to 1.60 mg/dL; P = 0.2), five days (one CCT: MD -1.02 mg/dL, 95% CI -2.24 mg/dL to 0.20 mg/dL; P = 0.1), and 12 days (one CCT: MD -0.80 mg/dL, 95% CI -2.51 mg/dL to 0.91 mg/dL; P = 0.36) after therapy. Pooled results from three CCTs showed higher frequency of adverse effects in participants who received urate oxidase (RR 9.10, 95% CI 1.29 to 64.00; P = 0.03).Another included RCT, with 30 participants, compared different doses of rasburicase (0.2 mg/kg versus 0.15 mg/kg). The primary outcome was not evaluated. No clear evidence of a difference in mortality (all-cause mortality (Fisher's exact test P = 1.0) and mortality due to TLS (no deaths in both groups)) and renal failure (no renal failure in both groups) was identified. It demonstrated no clear evidence of a difference in uric acid normalisation (RR 1.07, 95% CI 0.89 to 1.28; P = 0.49) and uric acid level at four hours (MD 8.10%, 95% CI -0.99% to 17.19%; P = 0.08). Common adverse events of urate oxidase included hypersensitivity, haemolysis, and anaemia, but no clear evidence of a difference between treatment groups was identified (RR 0.54, 95% CI 0.12 to 2.48; P = 0.42).The quality of evidence ranks from very low to low because of imprecise results, and all included trials were highly susceptible to biases.Authors' ConclusionsAlthough urate oxidase might be effective in reducing serum uric acid, it is unclear whether it reduces clinical TLS, renal failure, or mortality. Adverse effects might be more common for urate oxidase compared with allopurinol. Clinicians should weigh the potential benefits of reducing uric acid and uncertain benefits of preventing mortality or renal failure from TLS against the potential risk of adverse effects.

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