EXPRESS: Efficacy and tolerability of sequential COP and doxorubicin chemotherapy protocol for treatment of high-grade lymphoma in cats.

The COP/DOX protocol is well-tolerated and effective for feline high-grade lymphoma, with CR predicting significantly improved survival.

This retrospective study evaluated the efficacy and tolerability of a sequential COP/doxorubicin (DOX) protocol in 27 cats with high-grade lymphoma treated between 2005 and 2024. Cats received COP induction (vincristine, cyclophosphamide, prednisolone) weekly for 6 weeks, followed by DOX consolidation every 3 weeks for 6 doses. Gastrointestinal lymphoma was the most common presentation (33.3%). The overall response rate at 6 weeks was 77.7%, with 37.0% achieving complete remission (CR) and 44.4% partial remission (PR) during COP. One cat with stable or progressive disease on COP achieved PR with DOX. Four cats (14.8%) were non-responders. Median progression-free survival (PFS) was 98 days (IQR 41–141) and median survival time (MST) was 154 days (IQR 102–546). Cats achieving CR at DOX completion had markedly improved outcomes, with PFS of 554.5 days and MST of 546 days. High-grade adverse events were limited to grade 3 and 4 neutropenia (n=3 each) during COP, suggesting acceptable tolerability. Lymphocyte-to-monocyte ratio and response at DOX completion were significantly associated with both PFS and MST, providing potential prognostic markers. Results were comparable to previously published protocols. The authors conclude that COP/DOX is a well-tolerated and effective treatment option for feline high-grade lymphoma, with depth of response being a key prognostic indicator.

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