Phase I Clinical Trial of Vinorelbine in Tumor-Bearing Cats

Background Vinorelbine (VRL) has been investigated in dogs, but its use in cats has not been studied. Hypothesis/Objectives To determine the maximal tolerated dose (MTD) and dose‐limiting toxicity (DLT) of VRL in tumor‐bearing cats. Animals Cats were included in this prospective phase I trial if they had confirmed malignancy, received ≥1 VRL treatment, and had adequate follow‐up. Previous treatment was acceptable, but concurrent chemotherapy or radiotherapy was not permitted. Methods Using a modified phase I design, cats were enrolled in cohorts of 3 at a starting dosage of 9 mg/m2. Cats tolerating the first treatment well were eligible to receive additional VRL treatments at escalating dosages; escalations beyond the perceived MTD were permitted based on individual tolerance. Intended treatment interval was 7 days. Patient histories, physical examinations, and complete blood counts were performed weekly. Results Nineteen cats were included. Sixty‐one VRL treatments were administered. Median number of treatments was 2 (range, 1–9). Starting dosages were 9–12 mg/m2. Maximal dosage administered was 15.5 mg/m2. The MTD was 11.5 mg/m2. Acute DLTs were neutropenia, vomiting, and nephrotoxicity. Other notable toxicities were weight loss and anemia. Conclusions and Clinical Importance Vinorelbine is tolerated in cats at a weekly interval. Recommended starting dosage is 11.5 mg/m2. Neutropenia was transient, lasting