Sodium iodide I 131 treatment of dogs with nonresectable thyroid tumors: 39 cases (1990-2003).
OBJECTIVE
To determine outcome for dogs with nonresectable thyroid carcinomas treated with sodium iodide I 131 and identify factors associated with outcome.


METHODS
Retrospective case series. Animals-39 dogs.


METHODS
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
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 undergoing 131I therapy should be monitored for signs of bone marrow suppression.
Turrel
Jane M
JM
Veterinary Oncology Specialties, 1072 Valencia Way, Pacifica, CA 94044, USA.
McEntee
Margaret C
MC
Burke
Blaise P
BP
Page
Rodney L
RL
D000818:Animals; D004283:Dog Diseases / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D004285:Dogs; D005260:Female; D007457:Iodine Radioisotopes / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D009362:Neoplasm Metastasis; D011877:Radionuclide Imaging / Q000379:methods / Q000662:veterinary; D012189:Retrospective Studies; D013670:Sodium Pertechnetate Tc 99m; D016019:Survival Analysis; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery / Q000662:veterinary*; D013974:Thyroxine / Q000097:blood; D016896:Treatment Outcome
D007457:Iodine Radioisotopes; D013670:Sodium Pertechnetate Tc 99m; D013974:Thyroxine