Objective—To evaluate the characteristics and outcomes of dogs with stage I, II, III, or IV oral malignant melanoma treated by various types of radiotherapy.
Design—Retrospective case series.
Procedures—Medical records of dogs with oral malignant melanoma treated by radiotherapy (with or without adjunctive treatments) at a veterinary medical center between July 2006 and December 2012 were reviewed. Information regarding signalment, tumor location, disease stage, treatment protocols, adverse effects, and survival time were obtained from medical records and by telephone follow-up. Associations between variables of interest and outcome were analyzed.
Results—Dogs received orthovoltage x-ray (n = 68), megavoltage x-ray (39), or electron beam (4) radiotherapy. Adjunctive treatments included debulking surgery (n = 18), chemotherapy (39), or both (27). Median survival times for dogs with stage I, II, III, and IV melanoma were 758 days (n = 19), 278 days (24), 163 days (37), and 80 days (31), respectively, and differed significantly between dogs with stage I disease and those with all other disease stages. Among dogs with stage III melanoma, risk of death was significantly higher in those that received orthovoltage x-ray treatment than in those that received megavoltage x-ray treatment. Severe (primary or secondary) adverse effects were identified in 9 dogs.
Conclusions and Clinical Relevance—Median survival time was significantly longer for dogs with stage I oral malignant melanoma than for dogs with more advanced disease at the time of staging. The staging system used may be a useful tool for prognosis prediction in dogs undergoing similar treatment protocols for oral malignant melanomas.