Response rate to a single dose of vinblastine administered to dogs with treatment‐naive multicentric lymphoma

• Published in: Veterinary & comparative oncology Vol. 16; no. 4; pp. 636 - 641
• Main Authors: Harding, K., Bergman, N., Smith, A., Lindley, S., Szivek, A., Milner, R., Brawner, W., Lejeune, A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.12.2018
• Subjects: chemotherapy; large cell; lymphosarcoma; chemotherapy; large cell; lymphosarcoma
• ISSN: 1476-5810; 1476-5829
• DOI: 10.1111/vco.12433

Vincristine is included in vincristine, cyclophosphamide, doxorubicin and prednisone (CHOP) chemotherapy protocols, which are the gold‐standard treatment for high‐grade canine lymphoma. Vincristine can result in relatively high rates of gastrointestinal toxicity, whereas vinblastine is generally well tolerated and thus may represent an under‐utilized and minimally toxic alternative to vincristine. Our objective was to determine the response rate and toxicity associated with a single dose of vinblastine administered to dogs with treatment‐naïve, intermediate to large‐cell, multicentric lymphoma. Twenty client‐owned dogs were enrolled with signed owner consent. A Simon's minimax, phase II, two‐stage trial was performed to test the efficacy of vinblastine administered at 2 mg/m2 IV followed by a pilot trial of vinblastine at 2.5 mg/m2. No dogs were administered concurrent steroids or other chemotherapy. One out of 14 dogs receiving vinblastine at 2 mg/m2 demonstrated a partial response. Three out of five dogs demonstrated a partial response to vinblastine at 2.5 mg/m2. Gastrointestinal toxicity was infrequent and low grade for both groups. The majority of dogs (80%) in the 2.5 mg/m2 dosing group developed neutropenia 1‐week post administration. Vinblastine was well tolerated but minimally efficacious at a dose of 2 mg/m2 IV in dogs with treatment‐naive, multicentric lymphoma. Because of poor response rates, treatment at this dose is not recommended. A small subset of dogs administered 2.5 mg/m2 had significantly improved response rates (P = 0.04), suggesting that higher doses may have improved efficacy, although further research is indicated to confirm these preliminary findings.