Comparative evaluation of single fixed dosing and weight-based dosing of rasburicase for tumor lysis syndrome.

STUDY OBJECTIVE: To evaluate single fixed dosing versus weight-based dosing strategies for rasburicase to determine the minimum dose required to mitigate hyperuricemia in the treatment or prevention of tumor lysis syndrome. DESIGN: Retrospective medical record review SETTING: Academic medical center PATIENTS: A total of 373 patients with a diagnosis of a hematologic malignancy or solid tumor and who received at least one dose of rasburicase over a 6-year period between January 1, 2005, and February 18, 2011; 180 patients received single doses of 3 mg (38 patients), 6 mg (99 patients), or 7.5 mg (43 patients), and 193 patients received weight-based dosing. MEASUREMENTS AND MAIN RESULTS: Tumor lysis syndrome laboratory data were recorded at baseline and monitored up to 72 hours after initial rasburicase administration. Median baseline plasma uric acid levels were 6.85 mg/dl, 8.80 mg/dl, 8.00 mg/dl, and 9.20 mg/dl, respectively, in the 3-mg, 6-mg, 7.5-mg, and weight-based dosing groups. Treatment success was defined as a normalized plasma uric acid level (< 7.5 mg/dl) within 24 hours after receiving rasburicase. The mean weight-based dose was 0.16 mg/kg. Six rasburicase treatment failures occurred; two were in the 3-mg group, one was in the 6-mg group, and three were in the weight-based dosing group. At 24 hours after rasburicase administration, no statistically significant differences in treatment success were noted among groups (92.9% vs 97.6% vs 100.0% vs 98.0% in the 3-mg, 6-mg, 7.5-mg, and weight-based dosing groups, respectively, p=0.1238). CONCLUSION: The efficacy of all single fixed doses and weight-based dosing strategies evaluated in this study appear to be comparable in normalizing plasma uric acid levels within 24 hours of rasburicase administration. Although use of a 3-mg rasburicase dose may be the most cost-effective treatment strategy in managing hyperuricemia secondary to tumor lysis syndrome, the 6-mg dose resulted in lower sustained uric acid levels after rasburicase administration. Further analysis of patient specific factors contributing to the need for repeat rasburicase administration should be conducted in larger, prospective clinical trials.

Eribulin mesylate: a novel halichondrin B analogue for the treatment of metastatic breast cancer.

PURPOSE: The pharmacology, pharmacokinetics, clinical efficacy, safety, and administration of eribulin in patients with metastatic breast cancer are reviewed. SUMMARY: Classical chemotherapeutic agents for breast cancer have dominated treatment regimens even in the era of targeted therapy. Disease progression through these agents is often due to the development of resistance or lack of efficacy with these agents. Recently, a new nontaxane agent, eribulin mesylate, was approved for the treatment of metastatic breast cancer in patients who have received at least two prior chemotherapeutic agents. Eribulin is a member of a new class of synthetic cytotoxic agents derived from the Japanese sea sponge Halichondria okadai. Eribulin differs from other antimicrotubule agents in that it can bind to the microtubule cap and inhibit tubulin polymerization, leading to microtubule arrest. In Phase II clinical trials, eribulin demonstrated activity in extensively pretreated patients who had previously received an anthracycline, taxane, and capecitabine and had shown disease progression within the last six months of treatment. In a pivotal Phase III clinical trial of heavily pre-treated patients, patients who received eribulin versus the physician's treatment of choice showed a significant increase in overall and progression-free survival. Eribulin has a manageable adverse-effect profile, consisting mainly of neutropenia and fatigue. Eribulin has been associated with a low incidence of peripheral neuropathy. CONCLUSION: Eribulin, a novel synthetic antimicrotubule agent that binds to the vinca domain of tubulin and inhibits the polymerization of tubulin, offers a new treatment option for metastatic breast cancer or locally advanced breast cancer.