Clinical Efficacy and Tolerability of Sorafenib in Dogs With Advanced Carcinomas.

Advanced carcinomas in dogs present significant therapeutic challenges with limited treatment options and poor prognoses. Sorafenib, a multi-kinase inhibitor targeting RAF and receptor tyrosine kinases, has demonstrated antitumor activity and tolerability in preclinical veterinary studies; however, clinical data remain limited. This prospective, open-label cohort study evaluated the tolerability and clinical efficacy of oral sorafenib (6 mg/kg once daily) in 24 dogs with cytologically or histologically confirmed unresectable, recurrent, or metastatic carcinomas. Tumour response was assessed using RECIST criteria, and adverse events were graded according to VCOG-CTCAE v2.0. Stable disease at 1 month was observed in 14 of 18 evaluable dogs (77.8%), yielding an overall clinical benefit rate of 58.3%. Median time to progression and overall survival were 51 days (95% CI, 14-115) and 65 days (95% CI, 49-143), respectively. Dogs presenting with lameness (n = 7) showed significantly longer time to progression and overall survival than those without (p < 0.01). Adverse events occurred in 9 of 24 dogs (37.5%), primarily mild lameness (29%) and gastrointestinal signs. Weight gain at 1 month, observed in 66.7% of dogs, was significantly associated with clinical benefit (p = 0.005; OR = 45.0; 95% CI, 1.8-1127.7). Sorafenib was well tolerated and provided measurable clinical benefit in dogs with advanced carcinomas. Lameness may represent a prognostic biomarker, and weight gain may reflect a favourable clinical response. These findings support further investigation of sorafenib and other tyrosine kinase inhibitors in veterinary oncology.