Fixed-dose rasburicase 6 mg for hyperuricemia and tumor lysis syndrome in high-risk cancer patients.

BACKGROUND: Rasburicase is indicated for the initial management of plasma uric acid levels in adults receiving anticancer therapy who are at risk for acute tumor lysis syndrome (TLS) and subsequent hyperuricemia. The labeled dose is 0.2 mg/kg/day administered intravenously over 30 minutes for up to 5 days. Our institutional adult guidelines recommend rasburicase 6 mg for uric acid levels >8 mg/dL in most adults with TLS, or 4-8 mg/dL in high-risk patients. Repeat dosing is indicated for uric acid levels >4 mg/dL determined ≥12 hours following the initial dose.

OBJECTIVE: To determine the efficacy of a single dose of rasburicase 6 mg per institutional adult TLS guidelines to decrease uric acid levels to <4 mg/dL by day 3, as well as to determine the effect on serum creatinine and phosphorus concentrations. The secondary objectives were to evaluate the appropriateness of our institutional guidelines and identify TLS risk factors.

METHODS: The study was approved by the University of Maryland Medical Center Institutional Review Board. A retrospective review of all adults between July 2008 and February 2009 who received at least one 6-mg dose of rasburicase, with redosing, if indicated, before day 3, was conducted. Subsequent TLS monitoring over 7 days after initial dosing was recorded. Patients were excluded if dosing did not adhere to institutional guidelines.

RESULTS: We observed a decline in median uric acid levels from 9.2 mg/dL (interquartile range 8.1-10.4) on day 1 to between 1.8 (1.0-3.8) on day 3 and 3.8 mg/dL (2.1-4.4) on day 7 (p < 0.0001) with 2 patients requiring repeat dosing before day 3 (n = 34). The majority of the population was hyperuricemic (>8 mg/dL; 76%) or at high risk for TLS (85%).

CONCLUSIONS: A 6-mg dose of rasburicase effectively decreased uric acid to <4 mg/dL by day 3, rarely requiring repeat dosing, in a high-risk population.