Complete surgical excision of canine Mast Cell tumours (MCT) and Soft Tissue Sarcomas (STS) from limbs is often difficult or impossible to achieve. This study aims to examine the effectiveness of a combination of incomplete resection and post-operative radiotherapy for the treatment of canine MCT and STS located on limbs.

Cases with complete clinical records presented to the QVSH, University of Cambridge, over a five-year period were included in this study. Data extracted from the case records were patient signalment, tumour presentation, complete histopathology and grading where relevant, details on the surgery and radiotherapy performed in addition to any information from re-check consultations. Follow-up data was also obtained via an owner questionnaire.

Sixty-seven cases fulfilled the inclusion criteria, representing 27 MCT and 40 STS. The mean age at presentation was 6.2 years and 7.9 years from each group respectively. A hypofractionated radiotherapy schedule (4 fractions administered weekly to a total dose of between 3200 and 3600cGy) was used at a median interval of 4 weeks post-operatively. The mean disease free intervals (DFI) for MCT group and STS group were 61.5 months and 63.3 months respectively and mean survival times for each group were 61.4 months (MCT) and 67.9 months (STS). However, 75% of patients had not yet reached DFI due to lack of recurrence or metastasis of the original tumour to date or due to death from unrelated causes. Metastatic spread following treatment was the cause of death in more STS cases (20%) than MCT cases (7%). The size of the tumour at presentation, histological type, location on the limbs, time from presentation to first surgery and number of surgeries did not significantly affect the disease free interval in either group.

This study indicates that long-term disease free intervals and survival rates (mean > 5 years) can be achieved using hypofractionated radiotherapy on incompletely excised Mast Cell Tumours and Soft Tissue Sarcomas from the limbs of dogs.