GENERAL CONSIDERATIONS
+ Biologic Behavior
- 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