Evaluation of a high-dose chemotherapy protocol with no maintenance therapy for dogs with lymphoma

The purpose of this study was to evaluate the efficacy and toxicity of an intensified dose protocol with no maintenance phase for the treatment of canine lymphoma. Forty-nine dogs all weighing more than 15 kg were entered. Dogs were staged and treated with a modified version of the University of Wisconsin (UW)-Madison protocol for lymphoma. Modifications included increased dosages of cyclophosphamide (250 mg/m² compared to 200 mg/m²) and doxorubicin (37.5 mg/m² compared to 30 mg/m²), with no crossover to chlorambucil or methotrexate. After 25 weeks on protocol (17 treatments), therapy was discontinued and dogs were monitored for relapse on a monthly basis. Disease-free interval (DFI) and overall survival were compared to 55 historical controls treated with the UW-Madison protocol. The 2 groups were comparable with respect to age, sex, breed, stage, presence of hypercalcemia, and CD3 status; a trend toward more substage b dogs was present in the high-dose group ( P = .076). When comparing response rate, DFI, death due to disease, and death due to treatment-related toxicity, more dogs were dead due to toxicity ( P < .001; odds ratio = 8.8) in the high-dose group. Overall survival between the high-dose and control groups did not differ significantly ( P = .55) at 270 and 318 days, respectively. The intensified dose protocol is an option for owners who are willing to risk higher toxicity for a shorter protocol with no statistical difference in survival from the UW-Madison protocol.