Veterinary Society of
Surgical Oncology

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

ORAL SQUAMOUS CELL CARCINOMA

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