Radioiodine for Thyroid Carcinoma

2014/09 Clinical Features and Treatment Outcomes of 41 Dogs with Sublingual Ectopic Thyroid Neoplasia Broome M.R., Peterson M.E. and Walker J.R. J Vet Intern Med, 2014. 28(5): p.1560-8. BACKGROUND: Thyroid neoplasia is common in dogs, but there are few reports of dogs with ectopic, sublingual thyroid tumors. OBJECTIVES: To describe clinical features and outcomes of dogs with ectopic, sublingual thyroid neoplasia. ANIMALS: Five hundred and forty-four dogs with thyroid neoplasia. METHODS: This retrospective study reviewed the medical records of dogs referred for thyroid neoplasia between 1995 and 2013. Data extracted included signalment, extent of thyroid disease (eutopic or ectopic; metastasis), serum thyroxine (T4 ) concentration, treatment, and survival. RESULTS: Of 544 dogs with thyroid neoplasia, 41 (7.5%) dogs had ectopic sublingual thyroid tumors. The clinical features of these 41 dogs were similar to the cohort group of 503 dogs with eutopic or ectopic mediastinal thyroid tumors, but dogs with sublingual tumors were younger and less likely to have metastatic disease (15% versus 30%, P < .05). Of the 41 dogs, 28 received treatment: 21 with surgery (which included partial hyoidectomy in 13), 7 with radioiodine alone, and 13 with surgery followed by administration of radioiodine. Overall median survival was 562 days (range, 1-1,850 days). CONCLUSIONS AND CLINICAL IMPORTANCE: When compared with eutopic thyroid carcinomas, ectopic sublingual thyroid tumors generally have a less aggressive biologic behavior. Many dogs have prolonged survival, even without treatment, although death because of local tumor invasiveness or metastasis can develop in some dogs. Surgical thyroidectomy, including partial hyoidectomy, is generally effective for control of local disease. Administration of radioiodine, alone or in combination with surgical treatment, is recommended for multifocal disease or metastasis.

2006/08 Sodium iodide I-131 treatment of dogs with nonresectable thyroid tumors: 39 cases (1990-2003) J Am Vet Med Assoc. August 2006;229(4):542-8. Jane M Turrel, Margaret C McEntee, Blaise P Burke, Rodney L Page Abstract OBJECTIVE: To determine outcome for dogs with nonresectable thyroid carcinomas treated with sodium iodide I-131 and identify factors associated with outcome. DESIGN: Retrospective case series. Animals-39 dogs. PROCEDURES: A definitive or presumptive diagnosis of thyroid tumor was made on the basis of cytologic or histologic examination, abnormal accumulation of sodium pertechnetate Tc 99m during scintigraphy, or both, and dogs were treated with sodium iodide I-131. Dogs with cervical thyroid tumors were evaluated 3 to 6 weeks after ¹³¹I therapy, and residual tumor was resected when feasible. RESULTS: Prior to ¹³¹I therapy, 32 dogs had a solitary mass and 7 had metastases; 21 were hyperthyroid, 16 were euthyroid, and 2 were hypothyroid. Median survival time for dogs with local or regional tumors (ie, stage II or III) was significantly longer (839 days) than median survival time for dogs with metastasis (366 days). Tumor site (cervical vs ectopic), dose of sodium iodide I-131, age, body weight, treatment (¹³¹I therapy alone vs ¹³¹I therapy followed by surgery), and serum T4 concentration prior to ¹³¹I therapy were not significantly associated with survival time. Three dogs died of radioiodine-associated myelosuppression within 3 months after treatment, but no specific factor associated with development of toxicosis was identified. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that ¹³¹I therapy may result in prolonged survival times in dogs with nonresectable thyroid tumors, regardless of serum thyroxine concentration prior to treatment. Dogs undergoing¹³¹I therapy should be monitored for signs of bone marrow suppression.

2005/04 Radioiodide (¹³¹I) therapy for the treatment of canine thyroid carcinoma Aust Vet J. April 2005;83(4):208-14. A J Worth, R M Zuber, M Hocking Abstract OBJECTIVE: To assess the efficacy of radioactive iodine treatment (¹³¹I) for canine thyroid carcinoma, as both the sole therapeutic modality and as an adjunct to surgery. DESIGN: Retrospective analysis of case records from the Gladesville Veterinary Hospital Nuclear Medicine Service, Sydney, between August 1988 and December 2001. CASE DETAILS: The records of 65 dogs with thyroid carcinoma were analysed according to therapy and outcome. Forty-three dogs received radioiodide therapy, either as the sole therapeutic modality (32) or as an adjunct to surgery (11). Radioisotope therapy consisted of one to three doses of ¹³¹I with a dose range of 555 to 1850 MBq. For analysis, dogs were divided into groups according to therapy: no treatment, surgery alone, surgery with radioiodide therapy or radioiodide therapy alone. Mode of therapy, dosage of ¹³¹I, clinical staging and age were all independently analysed according to survival to compare efficacy or predictive value respectively. RESULTS: When radioiodide therapy was used as an adjunct to surgery, median survival was 34 months. Censored median survival time for dogs that received radioiodide alone was 30 months. Dogs that did not receive treatment had a median survival of only 3 months. Log rank statistical analysis indicated that mode of therapy was significantly correlated with survival but that clinical stage of disease was not. CONCLUSION: The authors conclude that ¹³¹I therapy is effective at extending survival time, both as a sole therapeutic modality and as an adjunct to surgery, in dogs with invasive canine thyroid carcinoma. Incomplete surgical resection may not prolong survival in dogs also receiving ¹³¹I therapy, however surgical resection with curative intent should be recommended as the first line of therapy for mobile thyroid carcinomas. Radioisotope therapy can be recommended for cases where surgery alone is considered unlikely to be curative because of metastatic disease or local invasion, or for cases where surgery has been attempted but complete surgical removal has not been achieved.

1995/09 Treatment Of Differentiated Thyroid Carcinoma In 7 Dogs Utilizing 131-I Vet Radiol Ultrasound. 1995 ;36(5):417-424. 46 Refs William H. Adams, Michael A. Walker, Gregory B. Daniel, Mark G. Petersen, Alfred M. Legendre Seven dogs with thyroid gland carcinoma were treated with ¹³¹I and hormone suppressive therapy either alone (3 dogs) or in combination with surgery (3 dogs) or ¹³⁷Cs teletherapy and chemotherapy (1 dog). Empirically chosen doses of 75 to 137 mCi of ¹³¹I were given orally (2 dogs) and intravenously (5 dogs). Adverse effects were limited to acute, transient bone marrow hypoplasia and pancytopenia. Nominal objective reduction in tumor volume or size and number of pulmonary metastases was observed in 4 dogs treated with ¹³¹I and thyroxine. Of these 4 dogs, 2 had stable disease for periods of 4 and 12 months while a third dog had stable disease for 27 months following two ¹³¹I treatments at 3 month intervals. The fourth dog had progressive disease. Two dogs with mediastinal metastases showed reduction in localization of ^99mTc-pertechnetate and radioiodine following 2 and 3 treatments using ¹³¹I. It appears that relatively high doses of ¹³¹I can be used safely for the treatment of canine thyroid tumors and that further investigation can be justified to define its efficacy.