Abstract Background Mast cell tumors (MCTs) in dogs pose therapeutic challenges that vary with histopathological grade. Hypothesis/Objectives Electrochemotherapy (ECT) alone would result in a clinically meaningful response in nonmetastatic cutaneous MCTs, with efficacy varying by tumor grade. Animals Twenty-nine client-owned dogs with 39 nonmetastatic cutaneous MCTs were treated at a veterinary oncology referral center. Tumors were classified as low grade (n = 27) or high grade (n = 12) according to the Kiupel system. Methods This retrospective cohort study evaluated outcomes after ECT as the sole treatment. The primary outcomes were complete remission (CR) rate, median survival time, and disease-free interval. Electrochemotherapy was administered using standardized protocols, with follow-up ranging from 30 to 1600 days. Results Overall complete remission rate was 79% (95% CI, 63.5-90.7). Complete remission was achieved in 100% of low-grade tumors (27/27; 95% CI, 87.2-100) versus 45% of high-grade tumors (5/12; 95% CI, 18.1-75.4). Median survival time was 1198 days (range 188-1920 days) for low-grade MCTs and 210 days (range 45-765 days) for high-grade MCTs (P = .001). Median disease-free interval was 1080 days (range 188-1920 days) and 455 days (range 45-865 days) for low- and high-grade tumors, respectively. Median tumor volume was 4.8 cm3; low-grade tumors were generally smaller. The average number of treatments was 1.1 for low-grade and 1.6 for high-grade tumors. Conclusions and clinical importance ECT is an effective local treatment for low-grade MCTs, offering outcomes comparable to surgical management. For high-grade tumors, its benefit is limited to small-volume disease where surgery is not feasible.
Ojeda et al. (Thu,) studied this question.