Osteosarcoma
Diagnosis &
Treatment 
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| Cats and Dogs differ in the way bone cancer matures and how treatment should be administered. Because of the rapid nature of osteosarcoma, treatment should be sought as soon as possible. The only trouble is that the most common sign, lameness and pain usually happens when it is already taken firm hold. It is also mistaken by owners at first as arthritis, stiffness or pulled muscle in which veterinarian care is usually not immediately sought.
Osteosarcoma is the most common long bone tumor in dogs and cats. This is a very
aggressive tumor causing lysis (disintegration of bone) or bone production or both. There is some degree of
soft tissue involvement and metastasis (transfer of the disease to another part of the body) is common in the early part of the disease.
Canine Osteosarcoma Treatment
There are several available options for the treatment of osteosarcoma. Chemotherapy
in combination with surgery are considered to be the primary therapy in dogs without
any detectable metastasis. Amputation or limb sparing will resolve the primary tumor
and resolve the pain and lameness associated with osteosarcoma. However, on cases where surgery alone is performed, 90% of affected dogs will die of metastasis within one year.
The goal of surgery is to remove the tumor along with a clean healthy cell margin. This is
usually accomplished by amputation. Limb sparing could also be done with insertion
of an allograft after removal of the affected segment of bone. An allograft is a graft of tissue taken from a donor of the same species sufficiently unlike genetically to interact antigenically.
Also, chemotherapy significantly prolongs the survival of dogs with osteosarcoma when used
in conjunction with surgery. Medicinally, Cisplatin alone or in combination with doxorubicin markedly
improves survival time to a median of 8-10 months with the percentage of dogs alive after
11 months at 50%. Carboplatin another drug with less renal toxicity has the same survival
time as Cisplatin.
Furthermore, radiation therapy is also used in the treatment of osteosarcoma. This is very important
for limb saving procedures, since it aids in local control after marginal resection (removal). It usually
provides pain relief after the 3rd or 4th session. This option is attractive for those
who do not want to pursue amputation procedures.
Most animals adapt mentally well to amputation. Probably because survival is a basic instinct and they do not have any social pressures associated with it. Physically, animals that are young and not overweight adjust the best.
As a veterinarian, I find that the immediate key to a successful amputation is the aftercare and the ability to keep the pet from licking or biting at the wound. Animals that are not compulsive in this manner require less care and heal more quickly with less chance of additional infection.
Feline Osteosarcoma
Unlike its canine counterpart it has a much lower
rate of metastasis and longer term survival can be expected with complete excision. Median
survival for cats with osteosarcoma is approximately 2 years with many cats outreaching that. Due to the slow metastatic rate, radiation therapy can play an important role in osteosarcoma that cannot be totally
excised. Though, chemotherapy is not routinely warranted due to the slow metastatic nature of feline
osteosarcoma, it should be considered in a case to case basis.
Conclusion
There is no other way at this time but to say that the prognosis is poor in pets for long term expectancy although cats fair much better. However, it is important to note that if a majority of the pain is relieved a pet can enjoy a fairly content life until other organs become involved. Therefore, routine examinations should be maintain to monitor how the body is coping and the speed of metastasis. -Dr. N. Lorica
 
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