Dogs

Osteosarcoma

Osteosarcoma is a malignant bone cancer; together with Ewing's sarcoma it accounts for most primary bone malignancies. There is a preference for the metaphyseal region of tubular long bones. 50% of cases occur around the knee. It is a malignant connective (soft) tissue tumor whose neoplastic cells present osteoblastic differentiation and form tumoral bone.

Prevalence

It is the 6th leading cancer in children under age 15. It affects 400 children under age 15 and 500 adults between the ages of 15-30 every year. Approxiately 1/3 of the 900 will die each year, or about 300 a year. A second peak in incidence occurs in the elderly, usually associated with an underlying bone pathology such as Paget's disease, medullary infarct, or prior irradiation. Unfortunately although 90% or more of those with osteosarcoma will have a limb-salvage surgery of their knee, because of infection, non-union, local recurrence and other reasons some will lose a limb after limb-sparring surgery.

Pathology

The tumor may be localized at the metaphyseal end of the long bones. Most often it affects the upper end of tibia or humerus, of lower end of femurus. The tumor is solid, hard, irregular ("fir-tree" or "sun-burst" appearance on X-ray examination) due to the tumor spicules of calcified bone radiating in right angles. Surrounding tissues are infiltrated.

Microscopically: Tumor cells are very pleomorphic (anaplastic), some are giant, numerous atypical mitoses. These cells produce osteoid describing irregular trabeculae (amorphous, eosinophilic/pink) with or without central calcification (hematoxylinophilic/blue, granular) - tumor bone. Tumor cells are included in the osteoid matrix. Cartilage may be present. Presence of immature blood vessels (sarcomatous vessels lacking endothelial cells) favors the bloodstream metastasizing. 1

Symptoms

This type of bone tumor will first appears as a lump in long bones. Muscles will start to become weaker as the affected bone part is not as strong as normal bones. Since it is a bone tumor, the feel of it is bony but muscles are not necessarily attached.

Causes

The causes of osteosarcoma are not known. Due to the rarity of osteosarcoma, it appears that a genetic predisposition exists which renders some individuals vulnerable to developing the condition. Questions remain about whether radium , or fluoride, in drinking water can act as "environmental triggers" for increasing the incidence of the disease.

Treatment

Standard therapy is a combination of limb-salvage orthopaedic surgery and a combination of high dose methotrexate with leucovorin rescue, intra-arterial cisplatin (with or without caffeine(Japan)), adriamycin, ifosfamide with mesna, BCD, etoposide, muramyl tri-peptite (MTP).

Classic treatment is Intra-arterial cisplatin with Adriamycin. Ifosfamide can be used as a adjuvant treatment if the necrosis rate is low.

3-year event free survival ranges from 50% to 75%. and 5-year survival ranges from 60% to 85+% in some studies. Overall, 60-65% treated 5-years ago(2000) will be alive today. Osteosarcoma as one of the lowest survival rates for pediatric cancer despite chemotherapy's success in osteosarcoma of 6 chemotherapies, interferon-alpha, interleukin-2, and being the prototype of solid tumors in cancer.

Treatment studies come from Children's hospital Boston, Memorial Sloan-Kettering, Children's Oncology Group, Italian Oncology Group, Japan, and MD Anderson in Texas.

Fluids are given for hydration.

Drugs like Krytril and Zofran help with nausea and vomiting.

Neupogen, epogen, Neulasta help with white blood cell counts and neutrophil counts.

Blood helps with anemia.

Prognosis

Prognosis is separted into three groups.

• Stage I osteosarcoma has a good prognosis(>90%) and just requires surgery.

• Stage IIb prognosis depends on the site of the tumor(proximal tibia, femur, pelvis, etc.) size of the tumor mass(in cm.), the degree of necrosis from neoadjuvant chemotherapy(beforeoperation chemotherapy), and pathological factors like the degree of p-glycoprotein, whether your tumor is CXCR4 positive, Her2 positive as these can lead to distant metastases to the lung. Longer time to metastases, more than 12 months or 24 months and the number of metastases and resectability of them lead to the best prognosis with metastatic osteosarcoma. It is better to have fewer metastases than longer time to metastases. Those with a longer length of time(>24months) and few nodules(2 or fewer) have the best prognosis with a 2-year survival after the metastases of 50% 5-year of 40% and 10 year 20%. If metastases are both local and regional the prognosis is different unfortunately. (see http://www.osteosarcomasupport.org/prognosis.htm) top two articles.

• Initial Presentation of stage III osteosarcoma with lung metastates depends on the resectability of the primary tumor and lung nodules, degree of necrosis of the primary tumor, and maybe the number of metastases. Overall prognosis is 30% or greater depending.

Canine Osteosarcoma

Osteosarcoma is the most common bone tumor in dogs and typically afflicts older large and giant breed dogs (for example, Greyhounds German Shepherds, and Great Danes). The most commonly affected bones are the humerus, the radius, the femur, and the tibia. Other sites include the ribs, the mandible, the spine, and the pelvis. Metastasis of tumors involving the limb bones is very common, usually to the lungs. The tumor causes a great deal of pain, and can even lead to fracture of the affected bone. Amputation of the leg is the initial treatment, although this alone will not prevent metastasis. Chemotherapy combined with amputation improves the survival time, but most dogs still die within a year. There are surgical techniques designed to save the leg, but they do not improve the prognosis. One key difference between osteosarcoma in dogs and humans is that the cancer is far more likely to spread to the lungs in dogs.

Osteosarcoma is also the most common bone tumor in the cat and most commonly affects the rear leg. The cancer is less aggressive in cats than in dogs, and therefore amputation alone can lead to a significant survival time.

Reference

• Morrison, Wallace B. (1998). Cancer in Dogs and Cats (1st ed.). Williams and Wilkins. ISBN 0-683-06105-4

External links

• Treatment Information from U.S. National Cancer Institute
• Support Group and Information for people with osteosarcoma
• Superior Survivial Seen with Osteosarcoma 2004

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