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Canine thyroid carcinoma in 4-year-old American bulldog: Medical oncology perspective

Article

Dr. Emily Manor provides the medical oncology perspective on this challenging oncology case.

Emily Manor, DVMLimited information is available on the benefit of systemic chemotherapy for canine thyroid carcinoma. Surgery and radiation therapy are considered effective at controlling local disease,1 but the utility of chemotherapy for systemic disease control remains largely unknown. Because of the high metastatic rate for thyroid carcinoma,2-6 systemic therapy is often used despite clear evidence of its efficacy.

After local therapy has been performed, the recommendation for systemic chemotherapy is often based on factors concerning the size of the primary tumor. The rate of metastasis is thought to increase with the size of the thyroid carcinoma; a necropsy study reported a 100% metastatic rate for tumors greater than 100 cm3, which corresponds to a tumor length of about 5 cm in each dimension.7 An additional study reported that the metastatic rate for bilateral tumors was 16 times that of unilateral tumors.8 Chemotherapy should be considered for patients with either one of these negative prognostic factors. In addition, systemic treatment is often recommended when a patient presents with gross metastatic disease or develops metastatic disease after local therapy. Finally, chemotherapy can be considered if local therapy is declined or not possible in the case of a nonresectable tumor.1

Responses (either partial or complete) to several chemotherapy agents have been reported including doxorubicin,9 cisplatin,10,11 mitoxantrone,12 actinomycin D,13 and chlorambucil.14 In most instances, doxorubicin or carboplatin are used when treating in the microscopic disease setting after local therapy. An evaluation of the oral tyrosine kinase inhibitor, toceranib (Palladia-Zoetis), in canine solid tumors reported a clinical benefit for 80% of the dogs with thyroid carcinoma.15 Toceranib shows promise for patients with extensive metastatic disease.

Chemotherapy has not, however, been shown to extend survival compared with local treatment alone.16 Thyroid carcinoma is typically a slowly progressive cancer, and even patients with metastatic disease can experience relatively long survival times (often 12 to 18 months after the detection of pulmonary metastatic disease). The decision to pursue chemotherapy should be made only after review of individual patient prognostic factors and thorough discussion with the owner.

References

1. Withrow SJ, Vail DM, Page RL. Tumors of the endocrine system. In: Withrow and MacEwan's small animal clinical oncology. 4th ed. St. Louis, Missouri: Elsevier;2007.

2. Brearley MJ, Hayes AM, Murphy S. Hypofractionated radiation therapy for invasive thyroid carcinoma in dogs: a retrospective analysis of survival. J Small Anim Pract 1999;40:206-210.

3. Harari J, Patterson JS, Rosenthal RC. Clinical and pathologic features of thyroid tumors in 26 dogs. J Am Vet Med Assoc 1986;188:1160-1164.

4. Carver JR, Kapatkin A, Patnaik AK. A comparison of medullary thyroid carcinoma and thyroid adenocarcinoma in dogs: a restrospective study of 38 cases. Vet Surg 1995;24:315-319.

5. Marks SL, Koblik PD, Hornof WJ, et al. 99mTc-pertechnetate imaging of thyroid tumors in dogs: 29 cases (1980-1992).  J Am Vet Med Assoc 1994;204:756-760.

6. Haley PJ, Hahn FF, Muggenburg BA, et al. Thyroid neoplasms in a colony of beagle dogs. Vet Pathol 1989;26:438-441.

7. Leav I, Schiller AL, Rijnberk A, et al. Adenomas and carcinomas of the canine and feline thyroid. Am J Pathol 1976;83:61-122.

8. Thon AP, Marks SL, Feldman ES, et al. Prognostic factors and patterns of treatment failure in dogs with unresectable differentiated thyroid carcinomas treated with megavoltage irradiation. J Am Vet Med Assoc 2000;216:1775-1779.

9. Ogilvie GK, Reynolds HA, Richardson RC, et al. Phase II evaluation of doxorubicin for treatment of various canine neoplasms. J Am Vet Met Assoc 1989;195:1580-1583.

10. Knapp DW, Richardson RC, Bonney PL, et al. Cisplatin therapy in 41 dogs with malignant tumors. J Vet Intern Med 1988;2:41-46.

11. Fineman LS, Hamilton TA, de Gortari A, et al. Cisplatin chemotherapy for treatment of thyroid carcinoma in dogs: 13 cases. J Am Anim Hosp Assoc 1998;34:109-112.

12. Ogilvie GK, Obradovich JE, Elmslie RE, et al. Efficacy of mitoxantrone against various neoplasms in dogs. J Am Vet Med Assoc 1991;198:1618-1621.

13. Hammer AS, Couto CG, Ayl RD, et al. Treatment of tumor-bearing dogs with actinomycin D. J Vet Intern Med 1994;8:236-239.

14. Leach TN, Childress MO, Greene SN, et al. Prospective trial of metronomic chlorambucil chemotherapy in dogs with naturally occurring cancer. Vet Comp Oncol 2012;10:102-112.

15. London C, Mathie T, Stingle N, et al. Preliminary evidence for biologic activity of toceranib phosphate (Palladia) in solid tumors. Vet Comp Oncol 2012;10:194-205.

16. Nadeau ME, Kitchell BE. Evaluation of the use of chemotherapy and other prognostic variables for surgically excised canine thyroid carcinoma with and without metastasis. Can Vet J 2011;52:994-998.

 

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