Stage III thyroid cancer is greater than 4 cm in diameter and is limited to the thyroid or may have minimal spread outside the thyroid. Lymph nodes near the trachea may be affected. Stage III thyroid cancer that has spread to adjacent cervical tissue or nearby blood vessels has a worse prognosis than cancer confined to the thyroid. However, lymph node metastases do not worsen the prognosis for patients younger than 45 years.
Stage III thyroid cancer is also referred to as locally advanced disease.
The following is a general overview of treatment for stage III thyroid cancer. Cancer treatment may consist of a combination of surgery, radioactive iodine treatment, and radiation therapy. Combining two or more of these treatment techniques has become an important approach for increasing a patient’s chance of cure and prolonging survival.
In some cases, participation in a clinical trial utilizing new approaches to treating thyroid cancer may provide the most promising treatment. Treatments that may be available through clinical trials are discussed in the section titled Strategies to Improve Treatment.
Circumstances unique to each patient’s situation influence which treatment or treatments are utilized. The potential benefits of multi-modality care, participation in a clinical trial, or standard treatment must be carefully balanced with the potential risks. The information on this website is intended to help educate patients about their treatment options and to facilitate a mutual or shared decision-making process with their treating cancer physician.
Patients with locally advanced thyroid cancer have a higher risk of cancer recurrence. Typically, cancer recurs because there are small amounts of cancer that have spread outside the thyroid gland and were not removed by surgery. These cancer cells cannot be detected with any of the currently available tests.
To help reduce the risk of cancer recurrence, patients with stage III thyroid cancer typically receive a combination of treatments in an attempt to eliminate as much cancer as possible.
Surgery for stage III thyroid cancer typically consists of removing the entire thyroid—a procedure called a total thyroidectomy—plus removal of affected lymph nodes. Researchers from Italy have reported that including aggressive surgery in the initial treatment of patients with locally advanced thyroid cancer improves survival. 
Total thyroidectomy is associated with a side effect called hypoparathyroidism, which is a low level of a hormone that is normally released from the thyroid called parathyroid hormone. Parathyroid hormone is important for maintaining calcium levels in the blood. Without a functioning thyroid, blood calcium levels become abnormally low, causing a variety of symptoms that typically include weakness and muscle cramps and tingling, burning, and numbness in the hands. This condition is called hypoparathyroidism.
Iodine is a natural substance that the thyroid uses to make thyroid hormone. The radioactive form of iodine is collected by the thyroid gland in the same way as non-radioactive iodine. Since the thyroid gland is the only area of the body that uses iodine, the radiation does not concentrate in any other areas of the body. The radioactive iodine that is not taken up by thyroid cells is eliminated from the body, primarily in urine. It is therefore a safe and effective way to test and treat thyroid conditions.
Research indicates that treatment with radioactive iodine improves survival for patients with thyroid cancer that has spread to nearby lymph nodes or to distant locations in the body. 
The development of more effective cancer treatments requires that new and innovative therapies be evaluated with cancer patients. Clinical trials are studies that evaluate the effectiveness of new drugs or treatment strategies. Future progress in the treatment of stage III thyroid cancer will result from the continued evaluation of new treatments in clinical trials.
Patients may gain access to better treatments by participating in a clinical trial. Participation in a clinical trial also contributes to the cancer community’s understanding of optimal cancer care and may lead to better standard treatments. Patients who are interested in participating in a clinical trial should discuss the risks and benefits of clinical trials with their physician. Areas of active investigation aimed at improving the treatment of stage III thyroid cancer include the following:
Radiation therapy uses high-energy rays to damage cells so that they are unable to grow and divide. Without the ability to replenish themselves, the cancer cells die. Similar to surgery, radiation therapy is a local treatment used to eliminate cancer cells in the area where the rays are focused, but cannot kill cancer cells that have already spread throughout the body.
External beam radiation therapy (EBRT): Conventional radiation therapy that is delivered with a machine that directs several high-energy beams at the area of the cancer is called EBRT.
Results from a clinical trial indicate that patients with locally advanced thyroid cancer treated with EBRT after surgery are less likely to experience cancer recurrence in or near the original site of cancer, which is called local-regional recurrence. When researchers directly compared treatment with and without EBRT, only 8% of patients treated with EBRT experienced a recurrence of their cancer compared to more than half (51%) of patients treated with surgery alone. Approximately nine out of 10 patients treated with EBRT survived 10 years or more after treatment without their cancer progressing in the thyroid area, compared to less than four out of 10 for the patients treated with surgery alone. 
Intensity-modulated radiation therapy (IMRT): IMRT allows radiation to be delivered more precisely with the use of the following advanced techniques:
- Three-dimensional scans of the cancer help determine where the radiation should be targeted.
- A rotating device delivers radiation from every point around the cancer, rather than only a few points as with conventional radiation therapy.
- Special blocking devices—called leaves—direct the radiation away from sensitive organs and toward the cancer.
IMRT appears to reduce the chance of injury to healthy body structures that are near the cancer while delivering higher doses of radiation to the cancer. In the treatment of thyroid cancer, this means that sensitive cells in the neck area—such as the cells that line the throat—may be spared from radiation damage, reducing side effects and improving quality of life.
Preliminary findings reported by researchers in New York suggest that IMRT is an effective treatment for select cases of thyroid cancer. However, long-term research is needed to confirm these findings. IMRT may be available through a clinical trial.
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Keum KC, Suh YG, Koom WS, et al. The role of postoperative external-beam radiotherapy in the management of patients with papillary thyroid cancer invading the trachea. International Journal of Radiation Oncology Biology Physics. 2006;Mar14:[Epub ahead of print].
Rosenbluth BD, Serrano V, Happersett L, et al. Intensity-modulated radiation therapy for the treatment of nonanaplastic thyroid cancer. International Journal of Radiation Oncology Biology Physics. 2005;63(5):1419-26.