Phase I dose escalation of doxorubicin chemotherapy in tumor-bearing equidae.

Abstract

BACKGROUND: There is no information on the use of doxorubicin in horses with tumors. OBJECTIVE: To determine dose-limiting toxicosis (DLT) and maximum tolerated dose (MTD) of doxorubicin in tumor-bearing horses. ANIMALS: Seventeen horses with 34 localized or multicentric advanced tumors. METHODS: Two-stage dose-ranging design involving intrapatient and interpatient dose escalation. Treatment protocol included 6 treatment cycles given at 3-week intervals with dosages ranging from 40 to 85 mg/m(2). Clinical signs, hematologic, and nonhematologic changes were evaluated. RESULTS: Total doses ranged from 1,127 to 2,900 mg in 12 horses that completed the assigned treatment protocols. The MTD was 75 mg/m(2). Hypersensitivity reactions and neutropenia were dose limiting. Hypersensitivity was dose-dependent but schedule invariant. Neutropenia was dose- and cycle-dependent but dose-escalation schedule invariant. Cardiotoxicity was not observed. CONCLUSION AND CLINICAL RELEVANCE: The recommended dosage of doxorubicin to treat horses is 70 mg/m(2) given at 3-week intervals as single agent. Adjunctive treatment with antihistamines and nonsteroidal anti-inflammatory drugs is recommended to control hypersensitivity.