Opportunities and challenges of active immunotherapy in dogs with B-cell lymphoma: a 5-year experience in two veterinary oncology centers

Introduction. CHOP-based chemotherapy represents the treatment cornerstone for canine B-cell lymphoma (BCL); however, cure is rare. We have been treating dogs with BCL with chemo-immunotherapy since 2011. Materials and methods. To better characterize safety and efficacy of immunotherapy, and to find the best candidates, we compared dogs treated with chemo-immunotherapy with dogs treated with CHOP-based chemotherapy. All dogs were completely staged and followed-up. Primary endpoints were time to progression, lymphoma-specific survival (LSS), and 1-, 2-, and 3-year survival rates. Results. Three hundred dogs were enrolled: 148 received chemotherapy and 152 chemo-immunotherapy. Among dogs with diffuse large B-cell lymphoma, the benefit of chemo-immunotherapy was particularly relevant in dogs with a high serum LDH, stage V, substage b, and in those not previously treated with steroids (median LSS, 480 vs85 days; P<0.001). The 1-, 2- and 3-year survival rates were 20%, 13% and 8% for chemotherapy, and 51%, 19% and 10% for chemo-immunotherapy. Among dogs with nodal marginal zone lymphoma, those having at least 3 of the aforementioned characteristics significantly benefited from chemo-immunotherapy (median LSS, 680vs 160 days, P<0.001). The 1-, 2- and 3-year survival rates were 30%, 16% and 10%for chemotherapy, and 55%, 28% and 10% for chemo-immunotherapy. Among dogs with follicular lymphoma, lack of immunotherapy was the only variable significantly associated with increased risk of tumor-related death. Immunotherapy was welltolerated. Conclusions. Overall, adding immunotherapy to a CHOP-based protocol improved outcome in dogs with BCL, regardless of histotype and evaluated prognostic factors. Moreover, the identikit of the best candidate for immune-therapy was delineated.