Squamous cell carcinoma (SCC) is a cancer of the surface layer of cells lining parts of the skin, lips, gums, and other mucous membranes. These cancers occur with some frequency on the face and mouth of domestic cats, classically within the mouth or under the tongue but may occur anywhere on the body. Squamous cell carcinoma may metastasize throughout the body (such as to the liver or lungs), however they are known for being locally invasive, growing large and spreading into nearby tissues.
Squamous cell carcinoma of the head is a particularly difficult cancer to manage as it is often very difficult to remove the entire tumor without significant quality of life issues for the cat. These cancers are minimally responsive to chemotherapy or radiation. Death from SCC usually occurs as a result of the primary mass preventing the cat from eating and causing pain and secondary infections. Despite aggressive therapy, survival time with this disease is generally measure in months.
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are commonly used to alleviate pain and reduce inflammation associated with SCC, and in some cases may slow tumor growth. In dogs, SCC is often responsive to therapy with toceranib (trade name Palladia). This drug is a monoclonal antibody that works by two modes of action: it directly inhibits the growth of certain cancerous cells by inhibiting a tyrosine kinase receptor on the cell surface; and it inhibits the cytokine “Vascular Endothelial Growth Factor” (VEGF) which prevents new blood vessels from developing and slows the growth of tumors. This study attempted to determine if therapy with toceranib was effective in treating feline oral SCC.
This study was designed as a retrospective case-control study examining cats or biopsies presented to a single center for treatment of oral SCC over a four year period. Included cats had a confirmed diagnosis of oral SCC, no prior radiation, surgery or chemotherapy. Cats were stratified into two groups based on toceranib use. Concurrent NSAID therapy (piroxicam or meloxicam) was allowed in both groups. 46 cats in total were included with 23 in each group.
Cats were evaluated for side effects of medication, disease progression, and overall survival. Kaplan-Meier survival curves were constructed to evaluate differenced in survival and progression-free survival in both groups.
Treatment with toceranib was found to increase survival time but more than 2.5 times compared to cats not treated with toceranib. A clinical benefit was seen in 56% of treated cats. Median survival time in toceranib treated cats was 123 days, compared to 45 days in untreated cats. Cats who achieved stable disease on toceranib responded significantly better than those who did not (201 vs 73 days). Cats treated with toceranib and an NSAID did better than cats with monotherapy. All cats who survived to one year post dx were treated with toceranib and an NSAID.
As this was a retrospective study, there were many variables that were not controlled for. Cats received different doses and schedules of toceranib, which may have influenced outcomes. Owner decisions to euthanize may also have affected outcomes.
This study presents data suggesting that toceranib therapy may be helpful in the management of oral SCC. Advantages to this therapy are multiple; it is orally administered, relatively inexpensive, and with limited side effects. While recent data suggests that intensive protocols (ie combined thalidomide, bleomycin, piroxicam, surgery and accelerated radiation therapy) may present an option for long term survival, toceranib may play a role in future protocols, or provide a less intensive and expensive option for owners. (MRK)