The primary therapy for all forms of thyroid cancer is surgery (see Thyroid Surgery brochure). The generally accepted approach at the present time is to remove the entire thyroid gland in what is called a total thyroidectomy. Some patients will have thyroid cancer present in the lymph nodes of the neck or upper chest. These lymph nodes are removed at the time of thyroid surgery or sometimes, as a later procedure. After surgery, patients need to be on thyroid hormone for the rest of their life (seeThyroid Hormone Treatment brochure). Often, thyroid cancer is cured by surgery alone, especially if the cancer is small. If the cancer is larger, if it has spread to lymph nodes or if your doctor feels that you are at high risk for recurrent cancer, radioactive iodine may be used to destroy any remaining thyroid cancer cells after the thyroid gland is removed. Please read the Thyroid Surgery brochure to learn more details about the risks and benefits of surgery, and what kind of recovery can be expected.
RADIOACTIVE IODINE THERAPY
Thyroid cells and most thyroid cancers absorb and concentrate iodine very readily. That is why radioactive iodine can be used so effectively to destroy all remaining normal and cancerous thyroid tissue after thyroidectomy (see Radioactive Iodine brochure). The procedure to destroy or ablate thyroid tissue is called a radioactive iodine ablation. This produces high concentrations of radioactive iodine in thyroid tissues damaging the DNA in the thyroid cells, eventually causing the cells to die. Since other tissues in the body do not efficiently absorb or concentrate iodine, radioactive iodine used during the ablation procedure has little or no effect on tissues outside of the thyroid. Two risks are known to happen. In some patients, the radioactive iodine can affect the glands that produce saliva and lead to a having a dry mouth. In other patients, when high dose of radioactive iodine are necessary, there may be a small risk of developing other cancers later. These risks are small but increase as the doses of radioactive iodine increase. The potential risks of treatment can be minimized by using the smallest dose possible. Balancing potential risks against the benefits of radioactive iodine therapy is an important discussion that you should have with your doctor if radioactive iodine therapy is recommended.
If your doctor recommends radioactive iodine therapy, your TSH will need to be elevated prior to the treatment. This can be done in two ways. The first is by stopping to take thyroid hormone pill (levothyroxine) for 4-6 weeks. This causes you to become hypothyroid and high levels of TSH will be produced by your body naturally. However, hypothyroidism causes fatigue that can sometimes be significant. To minimize the symptoms of hypothyroidism your doctor may prescribe T3 (Cytomel®, liothyronine) which is a short acting form of thyroid hormone that is usually taken after the levothyroxine is stopped until the final 2 weeks before treatment. Alternatively, TSH can be increased sufficiently without making you hypothyroid simply by injecting TSH into you! Recombinant human TSH (rhTSH, Thyrogen®) can be given as two injections in the several days prior to radioactive iodine treatment. The benefit of this approach is that you can stay on thyroid hormone and do not become hypothyroid. You may also be asked to go on a low iodine diet for 1 to 2 weeks prior to treatment (see Low Iodine Diet FAQ). This will leave your body iodine depleted which improves absorption of radioactive iodine, and helps maximize the treatment effect.
Once the TSH level is high enough, a pretherapy iodine scan is often done by administering a small dose of radioactive iodine. This scan determines how much thyroid tissue needs to be destroyed and allows the doctor to calculate how large a dose of therapeutic radioactive iodine needs to be administered. When used correctly, radioactive iodine therapy has proven to be safe and well-tolerated and it has even been able to cure cases of thyroid cancer that have spread to other parts of the body like the lungs.
TREATMENT OF ADVANCED THYROID CANCER
Thyroid cancer that spreads (metastasizes) to distant locations in the body occurs rarely but can be a serious problem. Surgery and radioactive iodine remain the best way to treat such cancers as long as these treatments continue to work. However, for more advanced cancers, or when radioactive iodine therapy is no longer effective, other means of treatment are needed. External beam radiation directs precisely focused X-rays to areas that need to be treated—often metastases to bones or other organs. This can kill or slow the growth of specific tumors. Cancer that has spread more widely requires additional treatment. New chemotherapy agents that have shown promise treating other advanced cancers are increasingly available for treatment of thyroid cancer. These drugs rarely cure advanced cancers that have spread widely throughout the body. However, they can often slow down or partially reverse the growth of the cancer. These treatments are usually given by an oncologist (cancer specialist) and often require care at a regional or university medical center.