General Considerations

•axial OSA comprises 25% of all OSA cases and 59% in dogs < 15 kg

•breed predisposition: ± Boxer

•sex predisposition: female with a male-to-female ratio of 1:2.1 in all sites except ribs and vertebrae

•OSA sites in the axial skeleton include:

•rib (10%-11% of axial OSA and 6.2% of all OSA cases)

•vertebrae (15%-16% of axial OSA and 3.2% of all OSA cases)

•mandible (27% of axial OSA and 3.2% of all OSA cases)

•maxilla (16%-22% of axial OSA and 3.2% of all OSA cases)

•scapula (2.4%-13% of axial OSA)

•skull (10%-54% of axial OSA and 2.3% of all OSA cases)

•nasal cavity or paranasal sinuses (9% of axial OSA)

•pelvis (4%-6% of axial OSA)

•behaviour of axial OSA is less aggressive

•tumor-free surgical margins are difficult with axial OSA due to location

•local tumor recurrence (80%) is more common cause of death than distant metastasis (7.4%)

Metastasis

•metastatic potential is lower in axial OSA v appendicular OSA

•11%-18% metastatic rate in dogs with axial OSA at diagnosis and 35%-46% at necropsy

•27%-45% metastatic rate for rib OSA

•17% metastatic rate for skull OSA

•metastatic rate is higher with rib and scapula OSA

•metastatic rate is lower with mandibular and maxillary OSA

•metastatic rate is higher telangiectatic OSA and telangiectatic OSA are usually large and incompletely resected

Prognosis

•MST 120-154 days, with a 12-month survival rate 26.3% and 24 month survival rate 18.4%

•chemotherapy does not influence metastasis or survival

•prognostic factors: breed, body weight (small), anatomic site (mandible), body weight (small), treatment option, and completeness of surgical excision

•MST is significantly decreased in Golden Retrievers with axial OSA (100 days v 182 days in pure bred dogs and 264 days in other dogs)

•MST is significantly decreased in dogs treated with palliative rather than curative-intent radiation therapy (79 days v 265 days)