Combined half-body irradiation and chemotherapy for two dogs with relapsed high-grade B-cell lymphoma.

This report describes two dogs with high-grade multicentric B-cell lymphoma that relapsed 3 months after completing a 6-month-long chemotherapy regimen with L-asparaginase, cyclophosphamide, doxorubicin, vincristine, and prednisolone (L-CHOP). Both were re-treated with L-CHOP, achieving complete remission (CR) before undergoing sequential half-body irradiation (HBI; 6 Gy per fraction to cranial and caudal body, 2 weeks apart). Caudal HBI caused grade 3 gastrointestinal toxicity in both dogs and grade 3 thrombocytopenia in one; however, both remain in CR at the time of writing this report (i.e., 483 and 490 days post-relapse). These findings suggest that combining HBI with chemotherapy may offer benefits in relapsed canine lymphoma, especially when dogs are in CR at the time of HBI.