Oral Squamous Cell Carcinoma in Cats

Oral squamous cell carcinoma is the most common oral cancer in cats. What is the prognosis, and what are the treatment options?

First, let us start with some information about oral squamous cell carcinomas in cats.

Oral squamous cell carcinoma typically affects older cats (median age of 9 to 11 years). There is no apparent sex predilection. Most cases occur in domestic shorthair cats; however, this is likely to reflect the popularity of this breed rather than true breed predisposition.

Cats typically present with a proliferative oral mass or ulceration lesion that is noticed by the owner, or clinical signs referable to the presence of an oral mass (such as hypersalivation or oral discharge, halitosis, dysphagia [difficulties eating], pain on opening the mouth, loose teeth, weight loss, eye or facial swelling). The tumour commonly arises from the gingiva and mucosa of the maxilla, mandible, tongue, sublingual area, or tonsillar region.

This cancer is very locally invasive. Bone invasion is common in cats and is usually severe and extensive. Metastasis (i.e. cancer spread) is uncommon; however, it may occur in the mandibular lymph nodes and lungs in up to 31% and 10% of cats respectively.

What is the prognosis? The prognosis for oral squamous cell carcinoma in cats is guarded with a median (average) survival time of less than one month. Most cats are humanely euthanised due to the inability to eat or pain associated with the oral mass.

Clinical stage and location are the most consistent and reliable prognostic factors. Tumours less than 2-cm in diameter (clinical stage I) and located in the rostral oral cavity (particularly mandible) have a more favourable prognosis, probably because they are more likely to be completely removed by surgery.

What are the treatment options? Therapies are aimed at local disease control. Unfortunately, no matter what treatment is pursued, in most cases, the prognosis is guarded.

Surgery Overall, the median survival time with surgery alone is less than three months, with a one-year survival rate of less than 10%. However, the best survival outcomes occur in cats with oral squamous cell carcinoma located in the mandible treated with surgery (i.e. radical mandibulectomy) ± radiation therapy. The average survival times reported with this approach is between 11 and 23 months. Occasionally, a cure is possible with complete surgical margins. However, owners will need careful counselling to ensure they understand that all cats will require a feeding tube placement after surgery, around one in four cats will never gain the ability to eat enough by mouth requiring a permanent feeding tube, and significant complications may arise from radical mandibulectomy.

Radiation therapy Radiation therapy alone is palliative and can alleviate pain in cats. The median survival times reported with radiation therapy alone is around 3 to 5.5 months. However, the prognosis is more favourable in small tumours (i.e. tumours less than 2-cm) and in cats that achieve complete remission, with reported median survival times of around 10 to 19 months. Various radiation protocols exist. The frequency and duration of radiation therapy treatment will depend on the personal preference of the treating radiation oncologist. In general, acute side effects are common but self-limiting. These include alopecia [hair loss], moist desquamation, oral mucositis, dysphagia and ocular side effects. Permanent late complications are rare, occurring in less than 5% of treated cats.

Palladia® Palladia® is an oral tyrosine kinase inhibitor that is administered every second day or every Monday, Wednesday and Friday. Palladia® ± non-steroidal anti-inflammatory drugs (such as meloxicam or piroxicam) showed improved outcomes. In one study of 46 cats, the biological response rate to toceranib was 57% and the median survival time was four months. However, the long-term survival remains poor, with only 6.5% alive at one year.

Chemotherapy Chemotherapy can be considered for cats with oral squamous cell carcinomas, but with low expectations in terms of a response to therapy and remission durations. Chemotherapeutics, where minimal responses have been seen, include doxorubicin, cyclophosphamide, carboplatin and mitoxantrone.

Piroxicam Piroxicam is a non-steroidal anti-inflammatory drug (NSAID) that can help improve quality of life and can be considered as a sole therapy or in combination with any of the above therapies; provided the cat has normal renal function. Piroxicam has anti-cancer activity against a variety of cancers in pets, particularly carcinomas. Piroxicam has also shown stabilisation of disease progression in 2 of 11 cats with oral squamous cell carcinoma and the use of NSAIDs in one study was also found to be correlated with longer survival. However, it should be considered with low expectations in reducing tumour burden. Piroxicam has been studied more extensively than other NSAIDs for pets with cancer, so it is my NSAID of choice. Piroxicam alone can be administered safely in tumour bearing cats long-term. Gastrointestinal toxicity (primarily vomiting) is usually mild and transient within the first month of therapy. Renal and hepatic toxicity is rare. However, if it is used in combination with other forms of therapy such as radiation therapy, chemotherapy or Palladia®, it may lead to a higher rate of toxicity.

Pamidronate Pamidronate is a bisphosphonate that binds to bone to inhibit bone breakdown and may help alleviate bone pain associated with oral squamous cell carcinoma. It is administered intravenously every three to four weeks. It is tolerated well in cats and can be safely administered as a sole therapy or alongside other treatment modalities (such as chemotherapy or radiation therapy). Pamidronate reduces proliferation of feline cancer cells in vitro and palliates cats with bone-invasive tumours, including oral squamous cell carcinoma.

Prednisolone Prednisolone is a corticosteroid that can be used instead of an NSAID when cats are clinically unwell from their cancer. Anti-inflammatory dosages can reduce the inflammatory cytokine release associated with cancer and make cats feel clinically better within 24-48 hours.

Vets, I hope this information helps you understand a bit more about the prognosis and treatment options for cats with oral squamous cell carcinoma. If you have a question about feline oral squamous cell carcinoma or have a case that you would like evaluated, please do not hesitate to get in touch. Email: [email protected].