Pulse - March 2023 - 10

DIMENSIONS IN SURGERY + CRITICAL CARE
DIMENSIONS IN SURGERY + CRITICAL CARE
ANIMAL SPECIALTY & EMERGENCY CENTER
ANIMAL SPE
TY & EMERGENCY CENTER
There is an large, expansile, solid mass (black asterisk) measuring (7.7 x 7.3 cm) epicentered at the level of the 7th rib with resultant osseous
destruction and tumoral necrosis resulting in extrinsic mass effect on the peripheral hepatic capsular margin.
post operatively her cough and severe lethargy returned. Thoracic
radiography demonstrated rapid progression of metastatic disease,
and humane euthanasia was elected.
Osteosarcoma is the most common primary bone tumor in dogs,
accounting for approximately 85% of tumors of the skeleton. Axial
skeletal osteosarcoma (such as rib osteosarcoma) are far less common
than appendicular osteosarcoma, and may have more aggressive
biologic behavior. Older, large breed dogs are most commonly
affected with two age peaks, one smaller peak at 18-24 months old
and a larger peak at 10 years of age.1
While for appendicular osteosarcomas,
complete surgical excision followed by chemotherapy is
associated with a median survival time of 12 weeks with a 1-year
survival rate of 17.0%, one study of axial osteosarcomas in dogs
(22 with rib osteosarcoma), reported a median survival time of just
twelve weeks with a one year survival rate of just 17.0%. Heyman et
al reported an increased metastatic rate with osteosarcomas of the
rib and cranium as opposed to other axial osteosarcomas including
mandibular and maxillary tumors.3
This case reported herein
reflects the findings of these aforementioned studies as our patient
survived just 3 months post-operative rib resection and chemotherapy
and experienced rapid pulmonary metastasis. This patient also
had an elevated ALP, which has been shown to be correlated to a
poorer prognosis, with every 100% increase in ALP level leading to
a 1.7 times increase in the hazard for death.2
While for appendicular osteosarcoma, patients usually present
with lameness and possibly fracture of the affected limb, those
with axial sarcomas present somewhat differently.1
Depending on
the location, they may present with pain, a mass, and/or localized
clinical signs affecting adjacent organs secondary to mass effect.
The most common treatment with the best outcomes for appendicular
osteosarcoma is complete surgical excision with adjunctive
chemotherapy and/or radiation.1
Unfortunately, at this time
there is limited literature comparing treatments for axial osteosarcoma
in canine patients, making it difficult to define an ideal
treatment protocol.
While this case modeled the usual demographics for rib osteosarcoma,
the most interesting and unusual aspect was the presentation
of what appeared to be an intrabdominal (liver) mass. Unfortunately
her disease rapidly progressed despite appropriate surgical
control and adjunctive chemotherapy. The current literature and
experiences from this case further demonstrate that a poor prognosis
can be expected with rib osteosarcoma, even with prompt and
adequate surgical intervention. P
References
1 Johnston, Spencer A., and Karen M. Tobias. " Musculoskeletal Neoplasia
and Limb-Sparing Surgery. " Veterinary Surgery: Small Animal, Elsevier, St.
Louis, MO, 2018.
2 Kruse MA, Holmes ES, Balko JA, Fernandez S, Brown DC, Goldschmidt MH.
Evaluation of Clinical and Histopathologic Prognostic Factors for Survival
in Canine Osteosarcoma of the Extracranial Flat and Irregular Bones. Veterinary
Pathology. 2013;50(4):704-708. doi:10.1177/0300985812471542
3 Heyman SJ, Diefenderfer DL, Goldschmidt MH, et al. Canine axial skeletal
osteosarcoma: a retrospective study of 116 cases (1986 to 1989). Vet Surg.
1992;21:304-310.
While for appendicular osteosarcoma, patients usually present
with lameness and possibly fracture of the affected limb, those
with axial sarcomas present somewhat differently.
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MARCH 2023
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Pulse - March 2023

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