Successful remission of a recurrent osteosarcoma in the second and third
metacarpal bones of a warmblood gelding after radiation therapy.
Abstract
A fifteen-year-old warmblood gelding was presented with recurrence of a
histologically confirmed osteosarcoma of the left second and third
metacarpal bones three years after initial diagnosis and treatment.
Initially, surgical excision was performed, followed by local injection
of carboplatin 11 weeks later. The horse was sound after surgery and was
used for low level dressage and jumping. Three years later, the horse
developed acute onset of lameness in the left forelimb and a painful
soft tissue swelling at the proximomedial metacarpal region. Radiographs
showed a spiculated periosteal reaction on the medial aspect of the
third metacarpal bone, indicating re-activation of the lesion.
Stereotactic radiation therapy was performed with a protocol consisting
of three fractions under general anaesthesia (Mo-We-Fr schedule), and a
total dose of 30 Gy. The technique used was volumetric modulated arc
therapy guided by cone beam computed tomography for daily positioning.
Following the radiation therapy, the horse became sound at walk and one
month later, it became sound at trot. Follow-up by veterinary
examination eighteen months after final treatment revealed no lameness
at walk and trot, and a stable radiographic appearance.