RESUMEN
Mast cell tumours (MCTs) are common canine skin neoplasia. While they generally occur as single tumours, multiple synchronous MCTs (msMCTs) of de novo/non-metastatic origin are reported in a proportion of the patient population. Where there is no evidence of metastasis or lymphatic spread, MCTs are effectively controlled by surgery and other local therapies. However, treatment of de novo msMCTs can be more challenging, especially when they occur in surgically difficult locations. Here, we report the use of tigilanol tiglate, a novel small molecule registered as a veterinary pharmaceutical for the local treatment of non-metastatic MCTs, in the treatment of patients with msMCTs presenting at three Australian specialist referral centres. We also present a meta-analysis of the literature to provide a better understanding of the prevalence of canine msMCTs. Notably, nine patients with a total of 32 MCTs were treated during the study. A complete response was recorded in 26 (81%) of the individual MCTs on Day 28 after a single tigilanol tiglate injection. Of the 6 initially non-responsive MCTs, one achieved a complete response after a further tigilanol tiglate treatment. A complete response was reported at 6 months in all 22 of the tumours that were evaluable and that had recorded a complete response at Day 84. For the literature meta-analysis, 22 studies were found with prevalence estimates of msMCTs ranging from 3 to 40%; when combined, these studies yielded 3,745 patients with a prevalence of 13% (95% CI 10; 16). Overall, the results demonstrate the utility of intratumoural tigilanol tiglate as an option for the treatment of multiple MCTs where multiple surgical resections would have been required.
RESUMEN
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.
