Orthovoltage Radiation Therapy of Oral Malignant Melanomas in 17 Dogs

Abstract

A retrospective study was conducted on 17 dogs with oral malignant melanoma treated with orthovoltage radiation therapy. The radiation therapy protocol was 8 Gy once a week for 4 weeks with a total dose of 32 Gy. Overall response rate to macroscopic lesions was 73.3%. The median progression free interval and median survival time for all dogs were 126 and 241 days, respectively. The median survival times for dogs with stage Ⅰ, Ⅱ, Ⅲ and Ⅳ were not reached, 258, 80.5, 115 days, respectively. Significant associations with survival time were found for presence of metastatic disease at the time of diagnosis (presence, 71 days vs. absence, 303 days), administration of surgical therapy (performed, 582 days vs. not performed, 164 days), therapeutic response (CR, 438 days vs. PR, SD, PD, 154.5 days). The side effects of the radiation therapy were observed in almost all cases, but most were mild. This study pointed out that our orthovoltage radiation therapy was an effective approach for canine oral malignant melanoma.