Introduction

Chemotherapy protocols containing cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) are commonly utilized for the treatment of high-grade lymphoma in cats. The aim of this study was to evaluate tolerability and efficacy of a COP/DOX protocol, where cats were intended to receive COP weekly for 6 weeks followed by doxorubicin every three weeks for 6 doses.

Methods

Records were retrospectively reviewed for cats with lymphoma treated at the University of Missouri from 2005–2020. Cats who received sequential COP and doxorubicin were included. Data collected included signalment, method of diagnosis, tumor location, staging and baseline diagnostics, drug dosages, adverse events, re-staging diagnostics and treatment response. Kaplan-Meier analysis was used to estimate median survival time (MST) and progression free interval (PFI).

Results

Twenty-one cats met inclusion criteria. Lymphoma localized to the gastrointestinal tract in 47.6% of cats. The number of cats achieving clinical remission (CR) and partial remission (PR) throughout COP were 8 (38.1%) and 8 (38.1%), respectively. Of the 5 PR cats at the completion of COP, one achieved CR on doxorubicin, for an overall response rate of 85.7%. Three cats did not respond to either drug. PFI was 87 days (range 29–998) and MST was 151 days (range 49–2207). High grade adverse events included grade 4 neutropenia (COP: n=3), grade 3 vomiting (doxorubicin: n=1), and grade 3 anorexia (COP: n=1, doxorubicin: n=1).

Conclusion

Toxicity, response rates, PFI, and MST are similar to previous reports. This COP/DOX protocol is an acceptable treatment option for cats with lymphoma.