A retrospective study of sinonasal tumors in 182 dogs treated with stereotactic radiotherapy (3 × 10 Gy) (2010‐2015)

BACKGROUND: Stereotactic radiotherapy (SRT) is an emerging treatment for sinonasal tumors in dogs. Reported results regarding tumor control and incidence of acute and late radiation morbidities are inconsistent. OBJECTIVES: To determine treatment efficacy and prognostic indicators of SRT in dogs with sinonasal tumors and to quantify acute and late radiation morbidities. ANIMALS: One hundred and eighty‐two client‐owned dogs with sinonasal tumors diagnosed cytologically, histologically, or radiographically that underwent SRT. METHODS: Single‐arm retrospective study by reviewing medical records of dogs treated with SRT (10 Gy × 3) between 2010 and 2015. Kaplan‐Meier analysis was used to determine overall survival (OST; from the first day of SRT to death by any cause) and disease‐specific survival times (DSST; OST but censoring tumor/treatment‐unrelated death). Tumors were staged using modified Adams criteria. RESULTS: Median OST and DSST of dogs treated with 1 course of SRT was 441 (95% CI: 389‐493 days) and 482 (428‐536 days) days, respectively with skin/oral cavity acute morbidities observed in 3% of dogs. DSST in dogs with stage 4 disease showed no statistical difference compared to other stages (P = .64). Oro‐nasal (n = 2) or naso‐cutaneous (n = 11) fistula development occurred in 7.1% of dogs with median time of 425 days (range: 83‐1733 days). Possible chronic rhinitis after SRT was recorded in 54 of 88 dogs (61%) where information was available. CONCLUSIONS AND CLINICAL IMPORTANCE: Results are comparable to other reports of treatment of SRT. Acute morbidities were minimal. Modified Adams stage scheme appeared to be inappropriate for prognostication for dogs with sinonasal tumors treated with SRT.