ORAL FIBROSARCOMA

Biologic Behaviour

•oral FSA is the 3rd most common canine oral tumor with an incidence of 7.5%-25.0%

•median age 7.3-8.6 years, but 25% dogs are < 5 years

•sex predisposition: ± male with a male-to-female ratio of 1.4-2.8:1

•site predilection: gingiva (usually on maxillary arcade between the canine and carnassial teeth) (56%-87%), hard palate (7%-17%), and buccal or labial mucosa (4%-22%)

•gross appearance: flat, firm, ulcerated, multilobulated, and deeply attached

•locally invasive into the gingiva and bone with local tumor recurrence after surgical excision common

•60%-65% dogs have radiographic evidence of bone involvement

•metastasis to the regional lymph node in 19%-22% and lungs in 6%-27% dogs

Treatment

•surgical techniques: mandibulectomy and maxillectomy

•FSA is poorly responsive to radiation therapy and chemotherapy

•radiation therapy can be used alone or in combination with surgical excision, but is considered palliative

•no known effective chemotherapeutic agent, but doxorubicin and piroxicam may have some effect

Prognosis

•local control is more important than metastatic disease with local recurrence the most common cause of death

•high-grade anaplastic oral FSA have a higher metastatic potential than low-grade FSA

•MST for both mandibular and maxillary oral FSA following surgical resection: 11 months with 12-month survival rate 25%-40% and local recurrence rate 46%

•MST following mandibulectomy: 10-12 months with 12-month survival rate 50% and local recurrence rate 10%

•MST following maxillectomy: 11-12 months with 12-month survival rate 21% and local recurrence rate 33%

•radiation therapy: MST 6-26 months

•radiation therapy and hyperthermia: 12-month survival rate 50%

HISTOLOGICALLY LOW-GRADE BUT BIOLOGICALLY HIGH-GRADE FIBROSARCOMA

Biologic Behaviour

•histologically low-grade but biologically high-grade FSA occurs predominantly in the maxilla (72%) of large breed dogs, especially Golden Retrievers (54%)

•histological appearance is benign (i.e., fibroblast proliferation with abundant production of collagen) and can often be interpreted as fibroma or low-grade FSA

•72% dogs have radiographic evidence of bone lysis

•metastasis to the regional lymph node in 20% and lungs in 12% dogs

Treatment

•surgical treatment: mandibulectomy and maxillectomy

•radiation therapy can be used alone or in combination with surgical excision, but is considered palliative

•no known effective chemotherapeutic agent, but doxorubicin and piroxicam may have some effect

Prognosis

•survival depends on early diagnosis and aggressive treatment

•prolonged survival times can be achieved with surgery, surgery and radiation therapy, radiation therapy alone, and radiation therapy and hyperthermia