Original Article DOI: 10.1111/j.1476-5829.2012.00324.x Evaluation of a 15-week CHOP protocol for the treatment of canine multicentric lymphoma J. H. Burton 1 , E. Garrett-Mayer 2 and D. H. Thamm 1 1 Animal Cancer Center, Department of Clinical Sciences, Colorado State University, Fort Collins, CO, USA 2 Hollings Cancer Center, Department of Medicine, Division of Biostatistics and Epidemiology, Medical University of South Carolina, Charleston, SC, USA Abstract Dose intense CHOP protocols have been shown to improve outcome for people with non-Hodgkin’s lymphoma, but evaluation of dose intense CHOP protocols for canine lymphoma is currently limited. The hypothesis of this retrospective study was that a 15-week dose intense CHOP protocol would have shorter treatment duration with similar efficacy to other doxorubicin-based multidrug protocols. Thirty-one client owned dogs with multicentric lymphoma were treated with a 15-week CHOP chemotherapy protocol with an overall response rate of 100% and a median progression-free interval (PFI) of 140 days [95% confidence interval (CI) 91 – 335 days]. Dogs that had two or more treatment delays had significantly prolonged PFI and overall survival in multivariate analysis. Dose intensity did not correlate with patient outcome. Dogs experiencing multiple treatment delays secondary to adverse events may receive their individual maximally tolerated dose while dogs with no adverse events may be underdosed. Future studies should focus on individual patient dose optimization. Keywords chemotherapy, dog, dose intensity Introduction Doxorubicin (DOX)-based, multidrug chemother- apy protocols such as CHOP (cyclophosphamide, DOX, vincristine and prednisone) are the most effective treatment for canine lymphoma, yet there has been no substantial improvement in patient outcome since the addition of DOX to these proto- cols nearly two decades ago. 1 Canine lymphoma is highly chemoresponsive, with reported remission rates of greater than 85% and survival times rang- ing from 8 to 12 months for most protocols. 2 – 4 Despite high remission rates, these protocols are rarely curative as half of the dogs treated will relapse and succumb to their disease within 1 year of diag- nosis and less than 25% of patients will experience remissions greater than 2 years. 5 Because treatment of lymphoma is largely palliative in nature, many pet owners are reluctant to commit the financial resources and time necessary to treat their pet with a weekly, multidrug protocol. Dose intensity (DI) is defined as the amount of chemotherapeutic agent(s) delivered over a unit of time. 6 It has been demonstrated that patient outcome is improved with administration of more dose intense chemotherapy regimens for a number of human malignances. 7 – 9 Two recent reviews of the literature examining DI of non-Hodgkin’s lymphoma treatment protocols in humans supports the theory that increased DI correlates with improved patient outcomes. 7,10 To date, there is little information examining the DI of chemotherapy protocols for canine lymphoma. A recent study published by Sorenmo et al. 11 examined a dose intense, maintenance-free CHOP-based chemotherapy protocol for dogs with lymphoma and found that time to disease progres- sion and overall survival (OS) were similar to what has been previously reported in the literature. A 15-week dose intense CHOP protocol was implemented at the Colorado State University Correspondence address: Dr Jenna H. Burton, Deparment of Clinical Sciences Colorado State University 300 W Drake Road Fort Collins, CO 80523, USA e-mail: jhburton@colostate.edu 306 © 2012 Blackwell Publishing Ltd