+ 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)