Early progression during or after cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy indicates poor outcome with rescue protocols in dogs with multicentric lymphoma

Abstract Background Dogs with lymphoma that fail cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy (CHOP) before completion of their protocol are commonly thought to have poor long‐term outcome, but no previous studies have evaluated the effect of early relapse on progression‐free interval (PFI) or overall survival time (OST) for patients undergoing rescue chemotherapy. Objective Correlate rescue treatment outcomes in dogs with multicentric lymphoma with outcomes after 1st‐line CHOP chemotherapy. Methods Data were collected from 6 previous retrospective or prospective studies in 187 dogs with multicentric lymphoma that received 1st‐line CHOP chemotherapy and then received either lomustine (CCNU), L‐asparaginase and prednisone (LAP), or rabacfosadine (RAB, Tanovea), with or without prednisone or L‐asparaginase. Results The PFI after initiation of CHOP chemotherapy was significantly associated with response rate postprogression, PFI, and postrescue survival time (ST) for both rescue protocols. Immunophenotype (B‐ vs T‐cell) was not significantly associated with response, PFI or OST for LAP but was significantly associated with response and PFI for RAB. Conclusion Dogs that experience short PFI during or after 1st‐line CHOP chemotherapy had lower response rates to rescue treatment, with shorter PFI and ST. Immunophenotype did not significantly affect outcome with LAP but was associated with PFI for RAB.