Squamous Cell Carcinoma in Cats & Dogs: The Multimodal Approach

The treatment of first choice for head & neck squamous cell carcinomas (SCC) in dogs and cats is surgical removal. However, the invasive growth pattern necessitates wide surgical margins, which can be detrimental to functional outcomes. Fortunately, surgery is a good option for many head & neck tumors in dogs and some smaller tumors in cats, as will be discussed by the other speakers in this VSSO maxillofacial session. There is however a considerable group of tumors not amenable for complete excision due to size or location. A combination of therapies may be more suitable for selected cases.

Cutaneous SCC of the head in cats can often benefit from a multimodal approach. Radiation therapy (RT), plesiotherapy, or photodynamic therapy (PDT) may be used as a primary treatment or in combination with surgery, avoiding major disfigurement and morbidity. In cases superficial (Tis or T1) SCC of the head, PDT can cure or greatly reduce lesion size for subsequent surgery or other local therapy. PDT or plesiotherapy can have advantages over RT because of less concurrent damage to surrounding tissues such as the eyes or deeper structures.

Oral non-tonsillar SCC in dogs is in many cases treatable with surgery or a combination of surgery and RT. Even invasive surgery (mandibulectomy, maxillectomy, glossectomy) can have good functional outcomes (see other VSSO-session lectures). Metastatic rate is low and median survival time (MST) after local treatment varies from 1-3 years. Surgery of lingual SCC’s in dogs has a higher recurrence rate and lower survival time (MST 216 days). Caudal pharyngeal and sublingual SCC may have a higher metastatic rate and typically has a high local recurrence rate, if operable at all. The high metastatic rate (>90% of cases) of tonsillar SCC makes it difficult to treat and locoregional treatment (surgery and/or RT) is considered merely palliative, with 1 year survival of generally <10%. Multimodal treatment, using surgery and RT and/or chemotherapy may improve outcomes with MST of 211-355 days in dogs.  [...]