Phase I and pharmacologic study of topotecan in patients with impaired renal function.

Abstract

To determine the toxicities, pharmacokinetics, and recommended doses of the topoisomerase I inhibitor, topotecan, in patients with varying degrees of renal excretory dysfunction. Fourteen patients with normal renal function [creatinine clearance (CrCl) > or = 60 mL/min] and 28 patients with varying degrees of renal dysfunction were treated with topotecan 0.4 to 2.0 mg/m2/d as a 30-minute infusion for 5 consecutive days every 3 weeks. Plasma and urine samples were obtained to determine the disposition of topotecan. In patients with mild renal dysfunction (CrCl = 40 to 59 mL/min), dose-limiting hematologic toxicity was observed in three of eight patients receiving topotecan 1.0 mg/m2/d and in two of five patients receiving topotecan 1.5 mg/m2/d. In patients with moderate renal dysfunction (CrCl = 20 to 39 mL/min), dose-limiting hematologic toxicity was observed in three of eight patients who received topotecan 0.5 mg/m2/d, and in two of four patients receiving topotecan 1.0 mg/m2/d; these events were more frequently observed in extensively pretreated patients. Pharmacokinetic analyses showed significant correlations between CrCl and the plasma clearance of both total topotecan [Spearman's correlation coefficient (r2) = 0.65, P = .00001] and topotecan lactone (r2 = 0.65, P = .00003). Mean systemic plasma clearance of total topotecan was significantly reduced in patients with mild (P = .04) and moderate (P = .00006) renal dysfunction. There was no evidence of changes in the pharmacodynamic relationship between topotecan exposure (AUC) and myelotoxicity. Dose adjustments are required in patients with moderate, but not mild, renal impairment. For patients with moderate renal dysfunction, the recommended starting dose of topotecan is 0.75 mg/m2/d for 5 days every 3 weeks. Moreover, extensively pretreated patients need further dose reductions.