Trans-perineal ultrasonographic monitoring of intravaginal transmissible venereal tumour regression with vincristine sulphate chemotherapy in dogs: a study of twelve cases

Abstract

Transmissible venereal tumour (TVT) grows mainly on the genitals of dogs. When such lesions develop in the vaginal passage, the process of clinical examination, diagnosis, and monitoring of therapeutic response are crucial in veterinary practice. The objective of this study was to investigate the usefulness of two-dimensional trans-perineal ultrasonography to monitor the therapeutic response of vincristine sulphate on intravaginal TVT in dogs. Twelve female dogs having lesions confirmed as TVT with cytological evaluation were used. TVT were categorized as multilobular (n=7), solitary (n=5), and heterogeneous (n=12). The maximum transverse diameter of tumour was assessed ultrasonographically while treating with vincristine sulphate 0.025 mg/kg, IV at weekly intervals. Owners were informed about the side effects of chronic vincristine sulphate chemotherapy such as development of pancytopenia, inappetence, and alopecia. Dogs were monitored for such adverse reactions during the study. The average maximum transverse diameter of tumour was 3.05±1.31 cm (range, 1.32 to 5.8 cm) before the treatment. A variation of therapeutic effect on tumour size was observed with trans-perineal ultrasonography. A significant reduction of the lesions was recorded between two to five weeks of the treatment in 11 dogs (P=0.00), with the highest reduction recorded one week after the treatment (P=0.01). Eight dogs showed thickened and hyperechoic foci on the vaginal wall with the highest average thickness of 0.36±0.08 cm after the complete remission of TVT. Based on the results in this study, it could be concluded that trans-perineal ultrasonography is a simple and noninvasive diagnostic modality to characterize and monitor the therapeutic effect of vincristine sulphate in dogs affected with intravaginal TVT in clinical practice.