Evaluation of prognostic markers for canine mast cell tumors treated with vinblastine and prednisone

Histologic grade 3 MCTs, MCTs with c-KIT mutations, MCTs with increased cytoplasmic KIT, and MCTs with increased Ki67 and AgNOR values were associated with decreased DFI and OS. Dogs with histologic grade 3 MCT had significantly increased DFI and OS when treated with chemotherapy vs. surgery alone. Although not statistically significant due to small sample sizes, MCTs with c-KIT mutations had increased DFI and OS when treated with chemotherapy vs. surgery alone.This study confirms the prognostic value of histologic grade, c-KIT mutations, KIT staining patterns, and proliferation analyses for canine MCT. Additionally, the results of this study further define the benefit of postoperative vinblastine and prednisone for histologic grade 3 MCTs.Canine cutaneous mast cell tumor (MCT) is a common neoplastic disease in dogs, accounting for 7–21% of all cutaneous neoplasms [1-4]. Canine MCTs have variable biologic behaviors, ranging from solitary benign masses that can be cured with surgery alone to systemic and potentially fatal metastatic disease [5-9]. Currently, surgical excision is the primary treatment modality for canine MCT. In the event of incomplete surgical excision or a non-resectable tumor, radiation therapy (RT) may be used as an adjunct local therapy, and in the face of multicentric, metastatic, or aggressive MCT, postoperative chemotherapy is commonly employed. Canine mast cell tumors have variable response rates to different chemotherapy protocols, and, as with any drug, there is potential for the development of serious adverse events as a result of chemotherapy administration[6,8]. Therefore, it is critical to identify patients that will benefit most from such treatments and to identify prognostic markers that are associated with specific treatment outcomes.Previously, our laboratory has evaluated the prognostic significance of several markers for canine MCT patients treated with surgery alone. In these studies we found that KIT staining patterns[10], c-KIT