GENERAL CONSIDERATIONS

Biologic Behaviour

•SCC is the 2nd most common oral tumor and accounts for 17%-25% of oral tumors in dogs

•mean age 8-10 years with no sex or breed predilection, but larger breeds are over-represented

•site predilection: gingiva rostral adjacent to incisors, mandibular premolars, and maxillary molars (35%-42%), buccal or labial mucosa (4.9%-7.3%), and hard palate (1.9%-3.1%)

•gross appearance: irregular, raised, and cauliflower-like ulcerated mass

•77% of dogs have radiographic evidence of bone involvement

•metastasis to the regional lymph node in < 10% and lungs in 3%-36% dogs

•regional lymph node and distant metastasis more common with tongue and tonsillar SCC (in up to 73%)

•papillary SCC in young dogs is locally invasive but rarely metastatic

TREATMENT

Surgery

•surgical techniques: mandibulectomy and maxillectomy

•canine rostral SCC curable (rostral to PM2)

Radiation Therapy

•SCC is a radiation responsive tumor

•median DFI 36 months

•MST 16 months

Chemotherapy

•no known effective chemotherapeutic agent for primary or metastatic SCC

•piroxicam alone has a 17% (3/17) overall response rate in dogs with oral SCC, including 6% (1/17) CR, 11% (2/17) PR, and 29% (5/17) SD

•cisplatin and piroxicam combination improves response rates with 56% (5/9) overall response rate but is associated with a high incidence of renal toxicity (41%)

Photodynamic Therapy

•photodynamic therapy using photochlor as a photosensitizer has been investigated in 11 dogs with oral SCC

•73% (8/11) CR with no local tumor recurrence after a minimum of 17 months

PROGNOSIS

General Considerations

•good prognostic factors: rostral location, young age, and maxillary SCC

•long-term survival and cure is possible with non-tonsillar SCC if rostral to PM2 or rostral tongue

•increased survival time in dogs < 6 years

Surgery

•MST for both mandibular and maxillary oral SCC following surgical resection: 18 months with 12-month survival rate 70%-84%, and local recurrence rate 15%

•MST following mandibulectomy: 19-26 months with 12-month survival rate 91% and local recurrence rate 10%

•MST following maxillectomy: 10-19 months with 12-month survival rate 57% and local recurrence rate 29%

Radiation Therapy

•MST for radiation alone is 16 months and 34 months when combined with surgery

•4 prognostic factors in dogs with non-tonsillar SCC treated with orthovoltage radiation therapy:

•tumors rostral to PM2 have a significantly better MST than caudal tumors (16 months v 12 months)

   •local tumor recurrence has a significantly worse response than primary SCC

•radiation portal size < 100 cm 2/m 2 has a significantly better outcome than portal size > 100 cm 2/m 2

•age < 6 years is associated with a significantly better outcome than dogs ≥ 6 years

•younger age is also a prognostic factor with megavoltage radiation therapy:

•MST 1,080 days if < 9 years v MST 315 days if > 9 years

Chemotherapy

•piroxicam is associated with low response rate, but median progression free interval is significantly better for responders (180 days) compared to dogs with SD (102 days)

•MST 237 days for dogs with oral SCC treated with piroxicam and cisplatin and MST is significantly improved in dogs with a response to chemotherapy (MST 272 days v 116 days)

Photodynamic Therapy

•good prognosis with results similar to radical surgery but more cosmetic with 73% cure rate