34th Annual Scientific Meeting proceedings

The most common oral tumour in cats is squamous cell carcinoma (SCC), with osteosarcoma being the second most common. Most of these tumours will be diagnosed by the cat’s primary care veterinarian during a dental procedure. It is critical to communicate with and educate our referring veterinarians about the work up and diagnosis of this disease. Recommendations for primary care veterinarians when an oral mass is found, a is to describe the mass and location and to take digital radiographs for the patient file. This will help to monitor if there is any growth in the mass and also to help communicate the size, shape and location of the mass to any other veterinarians seeing this cat. An incisional biopsy should be recommended to determine the definitive diagnosis. SCC can mimic dental disease, so rapid regional progression of dental disease should be viewed with suspicious for neoplasia in older cats. Unfortunately, many cases of oral SCC in cats are extensive prior to diagnosis and treatment. This is likely due to a combination of treatment delay and reluctance to treat this disease surgically.

An incisional biopsy, rather than an excisional biopsy recommended as part of the work up. Although is tempting the shave the mass off or to attempt to fully remove it. However, this strategy may lead to issues when planning a definitive treatment if this is a malignancy. The oral mucosa has a strong potential to heal quickly, and in cases where an oral mass has been removed by an excisional biopsy, the site of removal may not be evident by the time that the histopathology report is back. This can be problematic when trying to plan a wide resection of the tumour to include bone or radiation to the site because there are no landmarks of the previous mass.

SCC is an aggressive and often devastating disease in cats.(1,2) In some cases, the disease metastasizes to lymph nodes or distant sites.(3) However, local control is the mainstay of treatment and the major challenge of treatment is that it can be difficult to achieve clean margins of excision.

Reports in the literature and anecdotal evidence are limited but often suggest that cats do not do as well as dogs with mandibulectomy.(4) Because of this mandibulectomy is often not routinely recommended in cats. Northrup et al reported outcomes in 42 cats after mandibulectomy. A high acute complication rate was reported in that study, and the authors recommended aggressive postoperative supportive care, including the placement of a feeding tube at the time of surgery. Six cats in that study had >50% of both mandibles removed, and three of those six did not regain the ability to eat; five cats in total did not regain the ability to eat.(4) It is important to note that in that study, not all cats were treated with an immediate feeding tube at the time of surgery. It is my opinion that this should be routinely performed for mandibulectomies and maxillectomies and cats. There is some recent evidence that cats with maxillectomies will eat more readily post operatively. However, considering the ease of esophageal tube placement and the potential negative consequences of a cat not eating post operatively, this should be considered routine, with the e-tube removed if it is not needed. Even if it is not used for feeding, it can greatly facilitate the administration of medications post operatively by owners.

Radiation has been pursued as an alternative to surgery for cats with oral SCC. Unfortunately, the results have not been promising, with reported median survival times of 92 to 174 days with various protocols, including stereotactic radiotherapy, palliative radiation, and postoperative radiation. (5-7) Surgical excision followed by radiation therapy for the treatment of mandibular SCC has also been described in cats with a reported mean survival time of 14 months. (8) Palliative treatment with nonsteroidal anti-inflammatory drugs has been advocated; the reported median survival time with this strategy was only 44 days.(9)

Radical mandiulectomy is rarely reported in cats. We reported eight cats with mandibular neoplasia treated with subtotal or total mandibulectomy. All cats had feeding tubes placed at the time of surgery. Six cats regained oral feeding between 3 days and 3 months postoperatively, two cats never regained the ability to take in their nutritional requirements by mouth. The estimated mean survival time was 712 days, with four cats living longer than 1 year. Two cats died of tumor-related causes (local recurrence in both cases), and one cat died of aspiration, which was likely associated with a complication of the feeding tube or a consequence of mandibulectomy. Successful outcomes are possible with subtotal or total mandibulectomy in cats with aggressive supportive care and should be considered as a treatment option.(10)

Mandibulectomy techniques vary with surgeon preference and extent of disease. I generally prefer ventral approach to facilitate TMJ disarticulation and access to the mandibular artery as well as mandibular and retropharyngeal lymph nodes.(11)

There is also only a small amount of literature on maxillectomy in cats, with a recent study by Liptak et al that reported the outcome in 60 cats retrospectively. Common reported complications were hyporexia (20%) and incisional dehiscence (20%), with a median duration of hyporexia of 7 days. The median PFI and MST were not reached in this study. Local recurrence rates were 18.3% and 4.9%, respectively. Similar to mandibulectomy in cats, maxillectomy is feasible with a good outcome in most cases, but these cats require a lot of supportive care compared with dogs and the outcome is not universally favourable in all cases.

Preoperative blood typing and the availability of blood for transfusion is recommended prior to mandibulectomy or maxillectomy in cats.  Feeding tube placement is recommended in all cases of mandibulectomy and maxillectomy in cats because of the varying intervals between surgery and the willingness of cats to start eating on their own. These are often geriatric cats, and it is important that they receive adequate nutrition to promote healing of their surgical sites.

References

1. Gendler A, Lewis JR, Reetz J, Schwarz T. Computed tomographic features of oral squamous cell carcinoma in cats: 18 cases (2002-2008). J Am Vet Med Assoc. 2010;236:319-325.
2. Martin CK, Tannehill-Gregg SH, Wolfe TD, Rosol TJ. Bone- invasive oral squamous cell carcinoma in cats: pathology and expression of parathyroid hormone-related protein. Vet Pathol. 2011;48:302-312.
3. Soltero-Rivera MM, Krick EL, Reiter AM. Prevalence of regional and distant metastasis in cats with advanced oral squamous cell carcinoma: 49 cases (2005-2011). J Feline Med Surg. 2013;16(2): 164-169.
4. Northrup NC, Selting KA, Rassnick KM, et al. Outcomes of cats with oral tumors treated with mandibulectomy: 42 cases. J Am Anim Hosp Assoc. 2006;42:350-360.
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