Referral
A 1.5 year old male Bernese Mountain Dog with a history of an intermittent, progressing to persistent right forelimb lameness, of approximately 3 months.
Patient History
The patient was evaluated by his rDVM on 13/03/2026 for a mild weight-bearing lameness which was not appreciated during consult and rest for one week was advised. He represented for a persistent lameness localised to the right forelimb and meloxicam was trialled. This successfully resolved the lameness but was discontinued due to onset of diarrhoea. Lameness again recurred two months after initial presentation on 06/05/2026 and radiographs were done showing a mixed lytic/productive lesion of the right proximal humerus. Meloxicam was re-introduced along with gabapentin during referral process.
CT scan and bone biopsy was done 12/05/2026. Histopathology was consistent with a poorly differentiated mesenchymal tumour, with the diagnosis of osteosarcoma being made. He was subsequently referred to ONE for specialist care on 21/05/2026.
Diagnostics
Given the size and weight of the dog, stereotactic radiation therapy was discussed as the optimal limb sparing option, to be followed by adjuvant bisphosphonate and chemotherapy. A previous thoracic CT scan was done on 12/05/2026 which showed no evidence of metastatic disease.
Upon referral to ONE oncology service, a CT was repeated for reassessment of the lesion as well as for radiation planning purposes. This showed slight progression of the right proximal bone lesion, with a breach of the periosteum, though no overt fracture was present. On presentation, the lameness was progressive, though he remained very animated despite his grade 3-4/5 lameness.
Plan
A stereotactic radiation regimen of 3 X 9Gy fractions was initiated on 09/06/2026. This was very well tolerated and there were no noted side effects at the treated site. Adjuvant carboplatin chemotherapy was initiated on 29/06/2026 along with bisphosphonate infusions.
Outcome
Post radiation, the lameness fully resolved in 1-2 weeks and has not been evident on further presentations.
Stereotactic radiation therapy (SRT) 3 day course of treatment to the right proximal humerus
SRT was prescribed to the right proximal humerus as a non-surgical alternative. Treatment was delivered via volumetric arc therapy (VMAT).
27Gy in 3 fractions to the target volume
VMAT fields are used to provide excellent treatment, preserving healthy tissue and critical surrounding structures.
Daily cone beam CT was used to verify the accuracy and precision of treatment
15 minute treatment time including daily image guided radiation therapy (IGRT) used to verify the accuracy and precision of treatment
