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doxorubicin or to metronomic chemotherapy may be seen.
There are three specific companion animal oral tumours that bear separate consideration.
• Feline oral SCC - these are often locally extensive at diagnosis, and if not surgical are very resistant
to treatment, with median survival times of a few months. Even with surgery, recurrence is common, though for small tumours that can be treated with mandibulectomy and adjuvant radiation, survival times may be improved. RT alone does not appear to be effective in most cases. There is one small study evaluating systemic bleomycin chemotherapy along with radiation and surgery where outcomes may have been better, and toceranib (+/- NSAIDs +/- metronomic chemotherapy) may be of benefit
in some cats. The use of NSAIDs is recommended based on COX expression in feline SCC for potential anti-tumour effects as well as for analgesia.
WSV18-0152
ONCOLOGY
APPROACH AND MANAGEMENT OF ORAL TUMORS IN DOGS AND CATS
S. Ryan1, C. Cannon1
1The University of Melbourne, UVet Hospital, Werribee, Australia
APPROACH AND MANAGEMENT OF ORAL TUMOURS IN DOGS AND CATS
Claire Cannon BVSc (hons) DACVIM (Oncology) MANZCVS
Stewart Ryan BVSc (hons) MS DACVS MANZCVS University of Melbourne U-Vet Animal Hospital claire.cannon@unimelb.edu.au stewart.ryan@unimelb.edu.au
Learning objectives: Develop an approach to the diagnosis and staging of oral tumours in dogs and cats. Understand the principles of surgery for oral tumours, and indications for other treatments such as radiation therapy, chemotherapy or immunotherapy either as adjuncts to surgery or as sole treatments.
The most common oral tumours in dogs are melanoma, squamous cell carcinoma (SCC), and fibrosarcoma (FSA), though many other tumours can occur in the oral cavity including the tongue. In cats, 60-70% of oral tumours
are squamous cell carcinoma with fibrosarcoma being the second most common. General principles of staging and diagnosis apply regardless of tumour type. Although cytology may be diagnostic, given the difficulty of
FNA in a conscious patient, sedation/anaesthesia and incisional biopsy for histopathology is generally most appropriate. All the common tumours in dogs and cats have some risk of metastasis, so staging is indicated prior to surgery. CT is generally preferred to assess the primary tumour, local lymph nodes (LN) and lungs all at the same time. Abdominal imaging could be considered, especially for canine oral melanoma. LN palpation is
not sensitive or specific for metastasis and so cytology/ histopathology is recommended. However, identification of the ‘sentinel’ lymph node based on anatomy alone can be challenging. Metastasis to both ipsilateral and contralateral submandibular and retropharyngeal lymph nodes can be seen in dogs with malignancies of the head, including the oral cavity.
For tumours without distant metastasis, surgery (primary tumour +/- LN excision) is recommended where possible. However, oral tumours may be extensive at the time of diagnosis, especially those located more caudally in the mouth, precluding excision.
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  • Canine tonsillar SCC - unlike non-tonsillar oral SCC (with the possible exception of lingual SCC), tonsillar SCC is highly metastatic and aggressive in dogs. Often the diagnosis is made from a metastatic
lymph node which is externally visible, rather than the primary tumour in the tonsil. Survival times are generally short (months), even with treatment, though combinations of chemotherapy (usually carboplatin) and radiation therapy may achieve reasonable palliation. However, in those where the disease is diagnosed early (no metastasis, one tonsil affected), prolonged survival may be possible with treatment.
• Canine hi-low (histologically low grade biologically high grade) FSA - a subset of canine oral FSA will appear non-aggressive (low grade sarcoma or even fibroma or reactive fibrous tissue) and yet have very aggressive behaviour with rapid local growth and extensive tissue invasion. This syndrome seems to be more common in the maxilla of large breed dogs. If amenable to aggressive therapy, outcomes can still be favourable.
References:
Vail DM, Withrow SJ, editors. Withrow and McEwen’s Small Animal Clinical Oncology (5th edition) W.B. Saunders, Philadelphia, 2012 is recommended as a general resource
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