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Veterinarian Technician December 2009 (Vol 30, No 12)

Canine Osteosarcoma

by Marisa Rhyne, Douglas Hepler, PhD, Holly Greene, MS, Boel Fransson, DVM, PhD, DACVS

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    Introduction

    The prognosis for most osteosarcoma patients is grave. Most have a median survival time of 4 to 12 months, with or without treatment.2-5,7 The patient's prognosis and treatment options are discussed with the owner after evaluation of the patient and a physical examination and diagnostic results have been determined by a board-certified oncologist. Discussion with the owner regarding the correct treatment modality or combination of modalities for the patient is vital for clear communication and expectations. For example, a severely obese, arthritic dog may not do well after an amputation; therefore, medical management with palliative care may be the best choice.

    Surgery—Depending on the patient, surgical amputation can be appropriate for treating appendicular osteosarcoma. The patient should be evaluated by an experienced specialist (i.e., an oncologist or surgeon) to determine whether it is a candidate for amputation. A common client concern regarding amputation is the quality of life for three-legged animals, especially large dogs. Most dogs adjust quite well and fairly quickly to having three legs. The median survival time with amputation alone is approximately 4 to 6 months.1-3,5,8 Adjuvant chemotherapy can be used to delay the progression of metastatic disease. If the patient is not a good candidate for surgery or if the owner does not want to pursue it, medical management must be implemented.

    Chemotherapy—Chemotherapeutic drugs for treating osteosarcoma are used to alter the course of the metastatic disease process (i.e., slow down the metastatic component of the disease). Commonly used chemotherapeutic drugs include platinum drugs (i.e., carboplatin or cisplatin) and doxorubicin.5

    Immunotherapy—Immunotherapy is an increasing area of research in which autogenous vaccines are under investigation.a

    Pain Management/Analgesia—Because of the painful nature of osteosarcoma, pain management is critical to patient care. Pamidronate, an aminobisphosphonate, can be used in combination with other treatment options to provide analgesia.5,11 Studies are being performed to establish its efficacy. One study has shown a decrease in pain when pamidronate is used in conjunction with NSAIDs5 (anecdotally, many oncologists think there is value in controlling bone pain). Osteosarcoma is extremely painful, and finding a drug or combination of drugs to alleviate the pain can be difficult. Analgesia options include administration of opioids, NSAIDs, tramadol, amantadine, or gabapentin as well as radiation therapy.

    Radiation Therapy—Radiation therapy can be used as a palliative or definitive treatment. In treating osteosarcoma, radiation therapy is most often used for palliation, to eliminate or reduce pain. Radiation therapy does not prolong survival7 but can improve the quality of life by reducing pain. To alleviate pain, radiation therapy not only kills tumor cells and inflammatory cells but also decreases bone destruction caused by osteoclasts.4 Oral pain medications are administered after radiation therapy.

    The radiation therapy protocol should be designed by a board-certified radiation oncologist. Many protocols exist. One protocol uses two consecutive treatments of 8 Gy/day on days 0 and 1 for a total dose of 16 Gy.4,7 Another protocol uses three spaced treatments of 10 Gy/day on days 0, 7, and 21 for a total dose of 30 Gy.4,7 The treatment field generally involves the radiographic extent of the tumor with 2- to 3-cm margins on all sides.4,7 Generally, pain relief begins approximately 2 weeks after treatment and can last 2 to 4 months.4,5,7,11 If pain returns, the radiation oncologist may recommend repeating the previous radiation protocol. Retreatment is not performed if the owner declines it or if a fracture has occurred at the affected site. Radiation therapy protocols are designed to deliver an effective dose of radiation that is unlikely to cause significant acute effects. The adverse effects vary according to the patient and area being treated. With protocols involving two or three treatments, adverse effects are rare but may involve dry desquamation or alopecia.

    The Technician's Role

    Veterinary technicians must closely monitor patients that are sedated or under general anesthesia while undergoing surgery, diagnostics, chemotherapy, or radiation therapy. Bone affected by osteosarcoma can fracture easily, which is important to remember when affected patients are waking from anesthesia. To avoid a fracture, these patients should be placed in a cage or run under technician supervision.

    Veterinary technicians may also be responsible for client communication, which can help determine the patient's needs. Changes in the patient that are noticed by the owner can indicate the recurrence of pain and a need to adjust the treatment protocol. These changes include the eating and drinking habits of the patient, lethargy, lameness, or other signs of pain. In cases of appendicular osteosarcoma, the patient can be fitted with a sling before leaving the clinic to allow mobility but reduce pressure on the affected limb. The veterinary technician should describe the appropriate home care for the pet. The owner will need to know what to watch for to assess the pet's pain level. The owner will also need to inhibit the physical activity of the pet, even though the pet may feel better and appear to be nonpainful (likely because of pain medication). The owner must know that allowing the pet to use the affected limb in a normal capacity can result in a fracture.

    Conclusion

    Osteosarcoma is a serious and painful disease, but there are options for improving patient comfort. Although amputation is the most common recommendation, it is not always accepted by owners for financial or other reasons. When owners decline amputation, other options need to be presented to improve patient comfort. The most common option is multimodal pain management with various drug combinations and palliative radiation therapy. Regardless of the treatment protocol, the veterinary technician needs to be an advocate for the patient and its comfort.

    Acknowledgements

    The author would like to thank Dr. Philip Treuil and Leah Barbee, RVT, for their help and guidance with this article.

    1. Goldschmidt M, Thrall DE. Malignant bone tumors in the dog. In: Newton CD, Nunamaker DM, eds. Textbook of Small Animal Orthopaedics. Ithaca, NY: IVIS; 1985:887-898.

    2. Withrow S, MacEwen G. Small Animal Clinical Oncology. 3rd ed. Philadelphia: Saunders; 2001.

    3. Henry CJ. Osteosarcoma in dogs. Proc World Small Anim Vet Assoc World Congr 2007.

    4. Mayer MN, Grier CK. Palliative radiation therapy for canine osteosarcoma. Can Vet J 2006;47(7):707-709.

    5. Ogilvie G, Moore A. Managing the Canine Cancer Patient: A Practical Guide to Compassionate Care. Yardley, PA: Veterinary Learning Systems; 2006:112-114, 451-468.

    6. Todd-Jenkins K. ACVIM highlight: new therapies for canine osteosarcoma. Vet Forum 2007;24(9)13-14.

    7. Ramirez O, Dodge RK, Page RL, et al. Palliative radiotherapy of appendicular osteosarcoma in 95 dogs. Vet Radiol Ultrasound 2005;40(5):517-522.

    8. Goldschmidt M, Thrall DE. Malignant bone tumors in the dog. In: Newton CD, Nunamaker DM, eds. Textbook of Small Animal Orthopaedics. Ithaca, NY: IVIS; 1985:899.

    9. Kramer MT, Latimer KS, Rakich PM. Canine Osteosarcoma. University of Georgia College of Veterinary Medicine. Accessed November 2009 at www.vet.uga.edu/vpp/clerk/Kramer/index.php.

    10. Dernell WS, Ehrhart N, Liptak JM, Withrow SJ. Canine appendicular osteosarcoma: diagnosis and palliative treatment. Compend Contin Educ Pract Vet 2004;26(3)172-183.

    11. Fan TM, de Lorimer LP, O'Dell-Anderson K, et al. Single-agent pamidronate for palliative therapy of canine appendicular osteosarcoma bone pain. J Vet Intern Med 2007;21(3):431-439.

    aImpellizeri JA. Personal communication.

    References »

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