Efficacy of vinblastine for treatment of canine mast cell tumors.
BACKGROUND
The optimal dosage and clinical efficacy of vinblastine (VBL) for treatment of mast cell tumors (MCTs) in dogs has not been established.


OBJECTIVE
Single-agent VBL has antitumor activity against MCTs in dogs.


METHODS
Fifty-one dogs with nonresectable grade II or III cutaneous MCTs.


METHODS
Prospective, open clinical trial. Dogs were systematically allocated (by hospital record number) to receive IV treatment with VBL at a dosage of 2.0 mg/m2 (weekly for 4 treatments then biweekly for 4 treatments; VBL 2.0) or treatment with VBL at a dosage of 3.5 mg/m2 (biweekly for 5 treatments; VBL 3.5). The primary outcome measure was reduction in tumor size.


RESULTS
Twenty-five dogs were allocated to the VBL 2.0 group and 26 were allocated to the VBL 3.5 group. In the VBL 2.0 group, 3 (12%) had a partial response (PR) for a median of 77 days (range, 48-229 days). Overall response rate in the VBL 3.5 group was 27%. One dog (4%) had a complete response for 63 days and 6 dogs (23%) had a PR for a median of 28 days (range, 28-78 days). Toxicoses were uncommon in the VBL 2.0 group. Twelve (46%) dogs in the VBL 3.5 group had < 500 neutrophils/microL 7 days after treatment; 2 dogs with neutropenia developed concurrent fevers.


CONCLUSIONS
VBL, when used as a single-agent, has activity against MCTs in dogs although the response rate is lower than those reported for VBL-containing combination protocols. Further, findings suggest VBL at a dosage of 3.5 mg/m2 should be considered for use in future phase II/III trials.
Rassnick
K M
KM
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. kmr32@cornell.edu
Bailey
D B
DB
Flory
A B
AB
Balkman
C E
CE
Kiselow
M A
MA
Intile
J L
JL
Autio
K
K
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D004283:Dog Diseases / Q000188:drug therapy*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D008297:Male; D008415:Mastocytosis / Q000188:drug therapy*; D014747:Vinblastine / Q000008:administration & dosage / Q000627:therapeutic use*
D000970:Antineoplastic Agents; D014747:Vinblastine