Canine apocrine gland anal sac adenocarcinoma (AGASACA) comprises 17% of perianal malignancies in the dog. Despite local and systemic therapy, relapse is common. Evidence suggests varying expression of tyrosine kinase inhibitor targets in canine AGASACA. Objective responses to toceranib phosphate (Palladia®) have been reported. The purpose of this study was to evaluate progression and survival outcomes in dogs with AGASACA treated with toceranib. Medical records were retrospectively reviewed for response, outcome, and toxicity. Data was available for 83 dogs with a median age of 11 years and a median weight of 23 kg. Sixty percent of patients had presumed metastasis at the time of diagnosis. Twenty-four percent were hypercalcemic at the time of diagnosis. Seventy-seven percent received previous therapy including surgery, radiation, and chemotherapy. Toceranib was a first-line systemic agent in 48% of dogs, either adjunct to previous local therapy or as the sole treatment modality. Median toceranib dosage was 2.7 mg/kg with a median treatment duration of 126 days. Most adverse events were mild, but resulted in dose alteration and/or treatment holiday in 53% and drug discontinuation in 38%. Objective response rate was 62% with an additional 23% of patients experiencing stable disease. Twenty-two percent of patients were alive at time of statistical analysis, 23% died of disease, and 23% were lost to followup. Median overall survival time (OST) was 1395 days. Median progression-free survival (PFS) was 1247 days, including patients who received additional therapy after toceranib. Median progression-free interval (PFI) was 328 days. Response to toceranib was associated with previous treatment (p 0.026) and lack of previous steroid therapy (p 0.012). On multivariate analysis, only tumor size at diagnosis was prognostic for OST (p 0.018), although presence of metastasis at diagnosis showed a trend toward significance (p 0.055). Tumor size at diagnosis, lack of previous steroid therapy, and metastasis at diagnosis were all prognostic for PFI on multivariate analysis (p 0.01, 0.035, and 0.020, respectively). Neither response to toceranib therapy nor previous treatment (other than toceranib) were significantly associated with outcome.

This is the first study evaluating outcome and survival data in dogs with AGASACA treated with toceranib. Results suggest that toceranib may extend overall survival in dogs with AGASACA. Reported response rates and toxicity are similar to previous studies.

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