Abstract
Canine high-grade mast cell tumours (HGMCT) are associated with a poor prognosis, are inherently more invasive, and have higher rates of local recurrence. The primary aim of this retrospective study was to assess the efficacy of intratumoural tigilanol tiglate (TT) as a local treatment option. Eighteen dogs with mast cell tumours (MCT) cytologically diagnosed by veterinary pathologists as either high-grade or suspected high-grade MCT were treated with TT. The TT dose was based on tumour volume (0.5 mg TT/cm3 tumour volume) and delivered intratumourally using a Luer lock syringe and a fanning technique to maximise distribution throughout the tumour mass. Efficacy was assessed on the presence/absence of a complete response (CR) to therapy at days 28 and 84 using response evaluation criteria in solid tumours (RECIST). For dogs not achieving a CR after 28 days, the protocol was repeated with a second intratumoural TT injection. Ten out of 18 dogs (56%) in this study achieved and maintained a CR to at least 84 days after their first or second treatment. Six patients were alive and available for evaluation at 2 years, three of those were recurrence free, and a further three patients were recurrence free following a second treatment cycle. Tigilanol tiglate shows efficacy for local treatment of HGMCT, with higher efficacy noted with a second injection if a CR was not achieved following the first treatment. In the event of treatment site recurrence (TSR), the tumour may be controlled with additional treatment cycles. Tigilanol tiglate provides an alternative local treatment approach to dogs with HGMCT that would either pose an unacceptable anaesthetic risk or the tumour location provides a challenge when attempting surgical excision.
Highlights
Mast cell tumours (MCT) are a common canine skin cancer accounting for up to 21% of all skin tumours [1,2,3,4]
For most high-grade mast cell tumours (HGMCT) patients, the recommended mainstay of treatment is complete surgical resection of the lesion combined with chemotherapy as a systemic adjunct or alternatively, prophylactic irradiation of local lymph nodes [2, 13,14,15]
Study records from the US field study and from Australian studies were scanned for patients diagnosed with single cytologically confirmed HGMCT or suspected HGMCT treated with TT (1 mg/mL in buffered 40% propylene glycol) between 2013 and 2019 [29]
Summary
Mast cell tumours (MCT) are a common canine skin cancer accounting for up to 21% of all skin tumours [1,2,3,4]. Lesion proximity to critical structures, patient co-morbidities, anaesthetic risk, and financial constraints are factors that may limit the application of these treatment modalities in some clinical situations [1, 4, 8, 21]. In these situations, intratumoural therapy (which achieves high local drug concentrations of potent chemotherapeutics while minimising systemic toxicity) may provide a viable treatment option where surgical intervention alone is unlikely to be curative without additional therapy [22, 23]
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