Treatment of genitourinary carcinoma in dogs using nonsteroidal anti‐inflammatory drugs, mitoxantrone, and radiation therapy: A retrospective study

BACKGROUND: Locoregional tumor control and prolonged survival for dogs with genitourinary carcinoma (CGUC) reportedly are achievable using treatment with radiotherapy (RT) with or without adjunctive chemotherapy and nonsteroidal anti‐inflammatory drugs (NSAIDs). OBJECTIVES: To characterize event‐free and overall survival after treatment of CGUC using NSAIDs, mitoxantrone (MTX), and a standardized RT protocol (57 Gy in 20 fractions). ANIMALS: Fifty‐one client‐owned dogs treated between 2008 and 2017. METHODS: Dogs were retrospectively categorized into treatment groups: (a) first‐line concurrent chemoradiotherapy (≥1 dose of MTX started within 1 month of RT); (b) first‐line chemotherapy (MTX administered for >1 month before RT without tumor progression); (c) RT as a salvage procedure (MTX, surgery or both with subsequent locoregional tumor progression before RT). Treatment‐induced toxicoses, event‐free survival (EFS), and overall survival times (OSTs) were recorded. The influence of demographics, staging, and treatment‐related factors on survival was assessed using Cox proportional hazards modeling. RESULTS: Median EFS and OST for all dogs were 260 and 510 days with no significant differences among groups 1 (n = 39), 2 (n = 4), and 3 (n = 8). Both EFS and OST were shorter in dogs with moderate to severe clinical signs (P < .001 and P < .001, respectively); OST was shorter in dogs with prostatic involvement (P = .02). Permanent urinary incontinence developed in 16 dogs (31%) at a median of 70 days postirradiation; other toxicoses were mild and self‐limiting. CONCLUSIONS AND CLINICAL IMPORTANCE: Mild clinical signs and lack of prostate involvement were associated with favorable prognosis for survival. Client education regarding the risk of urinary incontinence is warranted.