2018 ACVIM Forum Research Abstract Program: Seattle, Washington, June 14 - 15, 2018

Complete remission was achieved in 5 horses (45.5%), partial response was achieved in 3 horses (27.3%), stable disease was achieved in 1 horse, and 2 horses died during treatment. Overall response rate was 73% (8/11). All 3 horses with EHV-5 associated lymphoma achieved complete remission. Two pregnant mares were treated, with one mare surviving to foaling. Overall median survival time was 13 months (range, 1 -41 months). Median survival time for multicentric lymphoma (n = 8) was 7.5 months (range, 1 -28 months) and median survival time for cutaneous lymphoma (n = 3) was 21 months (range, 16 -41 months). Seven of 11 horses exhibited a total of 11 adverse effects directly attributed to chemotherapy. Adverse effects were graded according to the VCOG-CTCAE grading system (grade 1 alopecia, n = 2; grade 1 combined neutropenia and lymphopenia, n = 2; grade 1 lymphopenia, n = 1; grade 1 lethargy, n = 1; grade 2 gastrointestinal signs, n = 1; grade 2 injection site reaction, n = 1; grade 2 hypersensitivity, n = 1; grade 4 hypersensitivity, n = 1; grade 5 hypersensitivity, n = 1). Higher grade adverse effects were most commonly associated with doxorubicin administration (n = 3), including one horse that died 18 hours post-administration. This report is limited by its retrospective nature, particularly the variation in treatment.