Ultrasound is a poor predictor of early or overt liver or spleen metastasis in dogs with high-risk mast cell tumours.

Conflicting evidence exists regarding the importance of routine abdominal ultrasound (US) with hepatic and splenic fine needle aspiration (FNA) cytology during staging of canine mast cell tumours (MCT). The objective of this study was to correlate ultrasonographic and cytologic findings in dogs with strictly defined high-risk MCTs and to determine the influence on outcome. Our hypothesis was that US poorly predicts visceral metastasis in high-risk MCTs and that early metastasis is associated with improved outcome when compared to overt metastasis. US of liver and spleen correlated to cytologic results, categorized as no metastasis, early metastasis or overt metastasis. Of 82 dogs prospectively enrolled, 18% had early visceral metastasis and 7% had overt metastasis on cytology; 67% with visceral metastasis had regional LN metastasis. US was a poor predictor of metastasis with sensitivity, specificity, positive predictive value and negative predictive value for the spleen of 67%, 68%, 21% and 94%, respectively and for the liver of 29%, 93%, 56% and 82%, respectively. Median time to progression (TTP) for dogs with no metastasis, early metastasis and overt metastasis was not reached, 305 and 69 days, respectively (P < .001). Median survival time (MST) for the 3 groups were not reached, 322 and 81 days, respectively (P < .001). High Patnaik or Kiupel grade, early metastasis, overt metastasis and adequate local control were significantly associated with outcome. Early visceral metastasis was associated with poorer outcome compared to dogs without metastasis, however, a subset of dogs experienced long-term control.

Tolerability of a rapid-escalation vinblastine-prednisolone protocol in dogs with mast cell tumours.

Optimal chemotherapy protocols for high-risk mast cell tumours (MCTs) are unknown. The purpose of this study was to determine the tolerability and toxicity profile of a rapidly escalating vinblastine and prednisolone protocol (VPP) in which 3.00 mg/m2 was administered once 7 days apart: at day 14 and at day 21. Dogs with chemotherapy-naïve MCTs presenting to the Oncology Service of a single institution were prospectively enrolled to receive escalating vinblastine, and haematology and a standardised quality-of-life questionnaire were assessed prior to each dosage. Thirty-four dogs were included: 30 with microscopic disease treated with adequate local therapy and four with macroscopic disease. Of 220 doses of vinblastine administered, 4% were associated with grade 3 and 4 toxicity. A total of 70% of dogs tolerated 3.00 mg/m2 given 7 days apart at day 14 and 21, although 29% of dogs developed dose-limiting toxicities and 8% discontinued the protocol due to toxicity. In conclusion, VPP was well-tolerated overall, although prior to further dose intensity optimisation, it is important to determine if dose intensity is linked to outcome in canine MCT to avoid unwarranted toxicity.