Additional local therapy with primary re-excision or radiation therapy improves survival and local control after incomplete or close surgical excision of mast cell tumors in dogs.

Abstract

OBJECTIVE: To compare survival and local recurrence outcomes in dogs with mast cell tumors with incomplete or close margins treated with primary re-excision or radiation therapy of the primary site versus no additional local therapy. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs (n = 64). METHODS: Outcomes of canine mast cell tumor cases that had incomplete or close surgical resection and presented to the Ontario Veterinary College Health Sciences Centre (2001-2010) were evaluated after additional local therapy (primary re-excision or radiation therapy) or no additional local therapy (comparison). Follow-up was performed through evaluation of medical records and telephone contact with referring veterinarians and owners. RESULTS: Tumors (n = 70) in 64 dogs were studied. Median survival times for the primary re-excision (2930 days) and radiation therapy (2194 days) groups were significantly longer than for the comparison (710 days) group. Local recurrence occurred in 13% of the re-excision group, 8% of the radiation therapy group, and 38% of the comparison group. Although local recurrence rate was not statistically significant for the re-excision group, time to local recurrence was statistically longer for both the re-excision and radiation groups. Adjunctive chemotherapy was not associated with improved survival or local control. CONCLUSION/CLINICAL RELEVANCE: There is significant improvement in survival and duration of local control when additional local therapy is performed after incomplete or close resection of mast cell tumors. These follow-up therapies should be recommended to owners when mast cell tumors are incompletely or closely resected.