Surgical removal is the treatment of choice in cases where the tumor has not deeply invaded other local structures such as major blood vessels and nerves making the procedure too risky.
Thyroid carcinomas appear to be poorly to moderately sensitive to chemotherapy alone.
External beam radiation has been shown to have good results for locally invasive tumors; however this treatment is not readily available for veterinary use.
Thyroid ablation using radioactive iodine (131I) is an effective therapy in parts of the tumor capable of taking up iodine.
In order to ascertain whether this treatment will improve your dog’s prognosis, a nuclear scan is first done. The dog is injected with the radioactive material, which is similar in structure to the 131I, and then scanned to see if the carcinoma takes up an appropriate amount. If this is the case, then it is concluded that the 131I is likely to be effective in destroying the tumor, regardless of its position. A recent study at our hospital has shown that the average survival time with this treatment alone is about 30 months whereas the average survival time with no treatment at all is about 3 months.
It seems that the only real disadvantage of this treatment is that your dog may be slightly radioactive for a few days after treatment and so must be kept in strict isolation. After this period the dog can go home to its normal environment, but we advise that owners not have prolonged contact with the dog for another week or so and discourage the dog from sleeping on the bed or sitting on someone’s lap for a prolonged period of time.
Dogs often need to be on thyroid replacement hormone for the rest of their lives.