Background: Most dogs receiving cytotoxic chemotherapy experience minimal side effects. However, in a subset of dogs, serious and life-threatening adverse events (AEs) occur. Limited evidence-based reports exist to quantify these AEs.
Hypothesis/
Objectives: The goal of this study was to identify the frequency and clinical consequences of AEs associated with commonly prescribed cytotoxic chemotherapy drugs in dogs.
Methods: Colorado State University’s Veterinary Teaching Hospital pharmacy records were searched to identify dogs prescribed doxorubicin, carboplatin, vincristine, vinblastine, cyclophosphamide, lomustine, mitoxantrone, or rabacfosadine between 1-1-2020 and 4-1-2024. Dogs were included in the study if the drug had been administered to the patient for the first time and as a single agent and adequate follow-up existed to assess acute AEs. AEs were grouped based on clinical consequence: no dose reduction indicated, dose reduction required, hospitalization needed, and death. Risk factors for severe AEs (SAEs) were evaluated via logistic regression.
Results: A total of 1,416 chemotherapy administrations to 823 dogs were evaluated. Overall, AE were absent to mild for the majority (n = 1,038, 73.3%) of treatments. Of the remaining treatments (n = 377), AEs from 71 (5%) were severe, resulting in hospitalization and/or death. Carboplatin was associated with the highest frequency (n = 22/319, 6.9%) of SAEs in this cohort. SAEs following carboplatin administration were significantly associated with age, cancer diagnosis (urothelial carcinoma), and elevations in BUN, phosphorous, and neutrophil count.
Conclusions and Clinical Importance: Chemotherapy is well-tolerated in most dogs, and carboplatin administration was associated with the greatest frequency of hospitalization and death.
