O03 - Vincristine-Induced Adverse Events as Related to Body Weight in Dogs Treated for Lymphoma

Background: Traditional dosing of chemotherapy based on body surface area (BSA) may overdose small dogs leading to increased incidence of adverse events (AEs).    

Hypothesis/Objectives: Objectives were to evaluate the incidence of hematologic and gastrointestinal AEs in dogs with naïve high-grade lymphoma treated with vincristine weighing ≤ 15 kg in comparison to dogs weighing > 15 kg. We hypothesized that dogs weighing ≤ 15 kg would experience a higher incidence of AEs.    

Animals: One-hundred thirty-eight chemotherapy-naive dogs with high-grade lymphoma treated with vincristine at standard doses.  

Methods: Multi-center retrospective study reviewing hematologic data and medical record information of dogs diagnosed with naïve lymphoma treated with vincristine. Complete blood counts were measured 24-hours before vincristine administration, then between 4-8 days post administration. Data were evaluated using logistic regression or ordinal logistic regression. 

Results: Thirty-eight dogs weighing ≤15 kg and 100 dogs weighing >15 kg were included. Seventeen (12.3%) instances of neutropenia occurred with no significant difference in overall incidence or grade between groups (P = 0.85). Thirty initially asymptomatic, substage A dogs (29.4%) experienced gastrointestinal AEs with no significant difference in overall incidence or grade between groups (P = 0.46). Seven instances of hospitalization occurred (5.0%) and the risk of hospitalization did not significantly differ between groups (P = 0.37). 

Conclusions and Clinical Importance: Vincristine dosed using BSA does not increase risk of either hematologic or gastrointestinal AEs in dogs weighing ≤ 15 kg. Clinicians can feel safe using standard doses of vincristine in dogs ≤ 15kg as the induction agent for lymphoma.