Evaluation of a multi-agent chemotherapy protocol combining dexamethasone, melphalan, actinomycin D, and cytarabine for the treatment of resistant canine non-Hodgkin high-grade lymphomas: a single centre's experience.

The DMAC protocol (dexamethasone, melphalan, actinomycin-D, cytarabine) has been evaluated in American studies for the treatment of relapsed canine lymphoma, comparing similarly to other rescue protocols. The aim of this study was to evaluate efficacy and toxicity of DMAC, in a larger UK cohort of resistant canine lymphomas. Medical records of dogs with resistant non-Hodgkin high-grade lymphomas that received DMAC as a rescue protocol were reviewed from 2007 to 2017. Response, time from initiation to discontinuation (TTD) and toxicity (Veterinary Cooperative Oncology Group criteria) were assessed. One hundred dogs were included; 86 received CEOP (modified CHOP including epirubicin) as first-line treatment. Thirty-five dogs (35%) responded: 21 complete responders (CRs) and 14 partial responders (PRs). Responders had significantly longer TTD (P < 0.001) compared with non-responders: 62 days (range 28-952) for CR vs 32 days (range 20-70) for PR. Six CR received more than six cycles of DMAC (range 7-36 cycles) and experienced a longer TTD (median 508, range 126-952 days). Thrombocytopenia occurred in 45% (24 grade 1-2, 21 grade 3-4) and neutropenia in 36% of cases (29 grade 1-2, 7 grade 3-4). Gastrointestinal toxicity occurred in 42% of dogs (40 grade 1-2, 2 grade 3-4). Owing to chemotherapy toxicity, treatment was discontinued in five, and hospitalization required in six cases. In this study, response to DMAC was lower and of generally shorter duration than previously reported. Toxicity was high, but infrequently led to hospitalization or discontinuation of treatment.