"Osteosarcoma of the Appendicular Skelton in Dogs"
TUMOR TIDBITS, A BIWEEKLY VETERINARY ONCOLOGY E-LETTER
Volume 2; Number 18; October 22, 2001.

Editor: Kevin A. Hahn, DVM, PhD, Dipl - ACVIM (Oncology) & Overall Nice Guy!
www.gcvs.com

THIS WEEK'S TUMOR TIDBIT:  OSTEOSARCOMA OF THE APPENDICULAR SKELETON IN DOGS

COMMON CLINICAL SIGNS - Lameness and pain at metaphyseal sites, particularly
distal radius, proximal humerus, proximal tibia, and distal femur; lytic and
productive bone lesion on radiographs.

COMMON HISTOLOGIC TYPES - Osteoblastic Osteosarcoma is most common; other
diagnoses are possible - chondroblastic, telangietic, and fibroblastic.
Other tumors may include fibrosarcoma, hemangiosarcoma, myeloma, and
metastatic carcinomas.

BIOLOGICAL BEHAVIOR - Large to giant breeds; no sex predilection; usually
middle-aged to old dogs; metastasis occurs early but may not be clinically
evident.

PROGNOSTIC FINDINGS - Without treatment, survival is poor either due to the
development of pathologic fracture or the rapid onset of distant metastasis;
prognosis is not correlated with gender, tumor site, or whether a
presurgical biopsy is performed.  

STAGING PROCEDURES - Prior to considering therapy, consider thoracic
radiography, abdominal ultrasonography and bone scintigraphy to evaluate for
the presence of visible metastases (poor prognostic sign) or serum bone
alkaline phosphatase (correlates with survival in some studies).

TREATMENT CONSIDERATIONS
Surgery: With amputation alone, median survival is 162 days; 11% of dogs are
alive at 1 year; limb sparing provides good limb function for distal radius
tumors but alone does not extend survival.

Radiation Therapy:  Radiation sensitive tumor but curative intent protocols
rarely considered due to poor prognosis; palliative use for pain control as
an alternative to amputation is considered good, median duration of pain
control is 8 months (treatment is every 2 weeks for 3 times).

Chemotherapy:  
Regardless if the limb is removed or not, various chemotherapy protocols
have shown efficacy in prolonging survival time: 

Cisplatin or Carboplatin once every 3 weeks for 4 treatments - 40%
to 60% of dogs alive at 1 year Doxorubicin every 2 weeks for 5 treatments - 50% of dogs alive at 1 year

WHAT DO WE DO AT GULF COAST?
In our patients, we recommend amputation if the dog can tolerate ambulation
on 3 legs comfortably.  In others, we recommend palliative radiation (3
treatments) to the tumor site for significant pain control and ambulation
(average 8-12 months).

In addition, we recommend Adriamycin (Doxorubicin) every 2 weeks for 5
treatments followed by a once monthly combination of Vincristine & Cytoxan
chemotherapy (along with supportive care medications such as Piroxicam and
Doxycycline (antimetastatic agents)) for 1 year.  In our patients, the
median survival is about 18 months).

ANY OTHER QUESTIONS ABOUT OSTEOSARCOMA?  Don't hesitate to call or email us
at Gulf Coast Veterinary Oncology!  We can forward additional info by email
if needed.