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CancerQuest > Introduction to Cancer Biology > Introduction to Cancer in Animals > Introduction to Cancer in Dogs > Canine Osteosarcoma

Canine Osteosarcoma

Introduction

Osteosarcoma (OSA) is a cancer that develops within bones.  It is often invasive and metastatic.⁽¹⁾   OSA is relatively rare in small domesticated animals, accounting for only 5-6% of canine malignancies.⁽²⁾   However, it is by far the most common primary bone tumor in dogs, accounting for 80% of cases.^{(2) (3)}

The diagram above highlights some of the bones affected by canine osteosarcoma.   This type of cancer occurs most commonly in the appendicular skeleton, including the radius and ulna, femur, tibia, scapila, humerus, and paw bones (phalanges).  The front limbs (forelimbs) are more likely to be affected than the rear (hind) limbs.  OSA also occurs in the axial skeleton, including the spinal bones, skull, jaw bone (mandible), and the vertebrae at the base of the spine (sacrum).  In rare cases, it can affect extraskeletal tissues, such as muscle.^{(2) (3)}  Because of its ability to metastasize, OSA can spread to other parts of the body.  Studies have shown that OSA invades the lungs in approximately 17% of cases.⁽³⁾

Risk Factors/Detection/Staging

Osteosarcoma is more common in adult dogs.  Large animals, weighing from 44 to 88 lbs (20 to 40 kg), are at a higher risk than smaller animals.⁽³⁾   

Signs of OSA in dogs include impaired movement due to pain and stiffness.  Affected dogs will often limp to avoid putting weight on the tumor-afflicted bone.  They also present with abnormal bone growth and swelling. 

Large tumor size is associated with poor prognosis.⁽⁴⁾  The location of the tumor can also affect the outcome of the disease.  Axial skeletal OSA and appendicular OSA tend to have similar prognoses.⁽⁵⁾   Tumors in the humerus bone tend to have a poor prognosis while tumors in the jaw tend to have better outcomes.⁽⁴⁾⁽⁵⁾

Treatment

Limb amputation is the standard treatment for OSA tumors located in the limbs.  Analgesics such as morphine are used to relieve pain, and most dogs can walk within 12-24 hours after the surgery.  Many dogs are able to adapt to the amputation within one month.  Interestingly, studies have shown that an owner's positive attitude can speed the adaptation process.⁽⁶⁾   Possible post-surgical complications include infection and recurrence of OSA in the stump.

Certain conditions can make dogs bad candidates for amputation, including arthritis, obesity, neurological problems and large breed.  For this reason, vets will perform limb-sparing surgeries, in which they remove the tumor and leave the surrounding tissue and bone intact.  This surgery has a higher rate of post-operation infection and OSA recurrence than amputation.  Studies reveal that the most common reason vets are asked to perform limb-sparing surgery is not based on the animals condition.  Rather, it is that owners are reluctant to proceed with amputation.^{(7) (8)}

Vets can use radiation as a curative treatment or to reduce pain and make the animal more comfortable (palliative care).  This type of therapy can reduce inflammation and heal micro-fractures.  Studies show that 70% of dogs respond positively to radiation therapy and experience pain relief.⁽²⁾

Chemotherapy drugs such as doxorubicin, carboplatin, cisplatin, or a combination of these drugs may also be used.  Chemotherapy alone has not been shown to extend survival time.  OSA-affected dogs treated with surgery and chemotherapy tend to survive longer.⁽⁹⁾

Unfortunately, despite the treatment options available, the prognosis for canine osteosarcoma is poor.  The estimated survival time is 6 to 12 months from the time of diagnosis, regardless of the treatment used.⁽¹⁾  The most common cause of death (or euthanasia) is disease spread (or metastasis).⁽⁷⁾

Acknowledgements: The above diagram was found using Creative Commons and can be accessed here.  It was obtained and modified on 8/10/09.

References for this page:

1. Thompson JP, Fugent MJ. Evaluation of survival times after limb amputation, with and without subsequent administration of cisplatin, for treatment of appendicular osteosarcoma in dogs: 30 cases (1979-1990). Journal of the American Veterinary Medical Association (1992) 200(4): 531-533. [PUBMED]
2. Endicott M. Principles of treatment for osteosarcoma. Clin Tech Small Anim Pract (2003) 12(2): 110-114 [PUBMED]
3. Cavalcanti JN, Amstalden EMI, Guerra JL, Magna LC. Osteosarcoma in dogs: clinical-morphological study and prognostic correlation. Brazilian Journal of Veterinary Research and Animal Science (2004) 41: 299-305. [http://www.scielo.br/scielo.php?pid=S1413-95962004000500002&script=sci_arttext]
4. Kuntz CA, Asselin TI, Dernell WS, et al. Limb salvage surgery for osteosarcoma of the proximal humerus: Outcome in 17 dogs. Vet Surg (1998) 27: 417-422. [PUBMED]
5. Straw AC, Powers BE, Kalusner J, et. al. Canine mandibular osteosarcoma: 51 cases (1980-1992). J Am Anim Hosp Assoc (1996) 32: 257-263. [PUBMED]
6. Kirpensteijn J, van den Bos R, Endenburg N. Adaption of dogs to the amputation of a limb and their owners satisfaction with the procedure. Vet Rec(1999) 144: 115118. [PUBMED]
7. Dernell WS, Straw RC,Withrow SJ. Tumors of the skeletal system in Withrow SJ, MacEwen EG (eds): Small Animal Clinical Oncology (2001) pp 378-417. [http://books.google.com/books?id=wprLBe_0U5QC&pg=PA1&lpg=PA410&dq=(7)%09Dernell+WS,+Straw+RC,Withrow+SJ.+%E2%80%9CTumors+of+the+skeletal+system%E2%80%9D&source=bl&ots=r7lhpEbD4G&sig=gjm3XGCGvaZEgnqIldi_-4OJDDI&hl=en&ei=bpSBSqvzLOG_tgfw2KTSCg&sa=X&oi=book_result&ct=result&resnum=4#v=onepage&q=(7)%09Dernell%20WS%2C%20Straw%20RC%2CWithrow%20SJ.%20%E2%80%9CTumors%20of%20the%20skeletal%20system%E2%80%9D&f=false]
8. Straw RC, Withrow SJ. Limb-sparing surgery versus amputation for dogs with bone tumors. Vet Clin North Am Small Anim Pract (1996) 26: 135143. [PUBMED]
9. Liptak JM, et. al. Canine Appendicular Osteosarcoma: Curative-Intent Treatment. Compendium on Continuing Education for the Practicing Veterinarian (March 2004) pp. 186-197. [http://animalcancersurgeon.com/Review_Articles_files/Compendium%202004%20OSA%20II%20curative-intent.PDF]