Most common types of thyroid cancer are “sporadic” or isolated, and not inherited. However, an uncommon type of thyroid cancer, medullary, can be familial, or run in families. When medullary cancer is inherited as a familial disease, it can be detected by a genetic blood test. Unless the disease is inherited, your children will not be affected.
Papillary thyroid cancer is the most common type of thyroid cancer. It is prevalent in women 30-40 years old and general thyroid occurrence in children. This cancer spreads to cervical lymph nodes and occurs in 70-80% of thyroid cancer patients.
Follicular thyroid cancer spreads to the lungs and bones through the bloodstream. It is more prominent in older populations and occurs in 10-15% of thyroid cancer patients.
Anaplastic thyroid cancer occurs in less than 5% of thyroid cancer patients. It is the most aggressive form of thyroid cancer and treatment is rarely effective.
Because its response to treatment is excellent, thyroid cancer grows very slowly and its spread to distant sites like lungs is uncommon. For example, the 20-year survival of the most common type, papillary thyroid cancer, is almost 95%.
The estimated number of new thyroid cancer patients for 2007 is 33,550 (incidence rate). This number is due to a continuing upward trend in the number of newly diagnosed thyroid cancer patients of 2% each year for more than 15 years! This represents an alarming and rapid percentage increase for any form of cancer, especially since most all other cancers are either stable or declining in their incidence rates. Fortunately, virtually the entire rate of increasing thyroid cancer patients annually is due to newly diagnosed papillary cancer (rather than other types of more aggressive thyroid cancer). The exact cause (or causes) is not clear; but, this rise in the incidence of papillary thyroid cancer has been attributed to better and earlier diagnostic imaging with ultrasound. However, other background environmental causes are difficult to exclude and there are continuing efforts to analyze this incidence trend.
The great majority of patients with thyroid cancer have a disease that can be successfully treated. In order to ensure your chances for successful treatment, it is important to receive treatment and follow-up care from those with a great deal of experience in the diagnosis and treatment of thyroid cancer. This is usually an endocrinologist, a doctor who specializes in hormone-related disorders.
You may be thinking, shouldn’t I be seeing an oncologist. The answer is not usually. The endocrinologist is the physician who deals primarily with the diagnosis, treatment, and follow-up of most patients with thyroid cancer. When standard therapy fails to control the progression of thyroid cancer and chemotherapy is being considered, then consultation with an oncologist is appropriate.
What treatment will I require?
Treatment depends on the type and extent of cancer. Treatment options include surgery, radioactive iodine, external radiation (see below), and chemotherapy. All patients require thyroid surgery and many receive radioiodine after surgery. External radiation is sometimes necessary when tumors cannot be removed surgically or eliminated by radioactive iodine.
What kind of surgery?
Removal of part or all of the thyroid gland (thyroidectomy) is the first step in management. Affected lymph nodes are also removed. A surgeon who has experience with thyroid cancer is the best choice for performing your surgery.
Will I require radiation? What type?
Conventional radiation therapy, the type that is generally used for cancer is not used very often to treat thyroid cancer. It is reserved to treat thyroid cancer that cannot be removed surgically or eliminated with radioactive iodine. Fortunately, it is only required to treat a small minority of thyroid cancer cases. This type of radiation treatment is often referred to as external radiation therapy because the source of the radiation comes from outside the body.
Most often patients with thyroid cancer who require radiation treatment receive radioactive iodine. This type of radiation works internally once it enters your body. It is administered by either swallowing a capsule or drinking a radioactive liquid; containing a radioactive form of iodine.
Radioactive Iodine Therapy
What is the purpose of radioactive iodine therapy?
Radioactive iodine eliminates the small amount of normal thyroid tissue that is typically left after thyroid cancer surgery. It is also given to destroy thyroid cancer in your neck that could not be removed by your surgeon, in addition to cancer that is outside of your neck that was not operated on. The purpose of the therapy is to treat remaining cancer and thereby reduce the chances for cancer recurrence. Although radioactive iodine is effective for many cases of thyroid cancer, it does not work for all cases and types of thyroid cancers.
Will my hair fall out?
Hair loss is not a direct side effect of radioactive iodine therapy. Temporary, mild hair loss may occur around the time of radioactive iodine therapy. This is the result of briefly having low thyroid hormone levels around the time of therapy.
If I require radioactive iodine how much will I get?
Doctors may take pictures, known as scans, of your whole body after you take a small amount of radioactive iodine. The radioactive iodine used for diagnostic scans is not only a lower amount, but also sometimes a weaker form of radioactive iodine than what is given to treat thyroid cancer.
How will I get ready for radioactive iodine therapy? Do I have to have low thyroid hormone levels and how will that make me feel? Is there a special diet?
Your doctor will tell you how and when to stop your thyroid medication. This will make you have low thyroid hormone levels and become “hypothyroid.” Becoming hypothyroid is required to make another hormone in your body, called thyroid stimulating hormone (TSH), rise. Elevated TSH levels stimulate thyroid cancer cells to take up radioactive iodine. You may develop symptoms due to this such as fatigue, constipation, and puffiness. In addition, you may start to feel cold, have muscle cramps, “pins and needles” sensations in your hands, feel depressed, and have difficulty concentrating.
A week to two weeks before your treatment you may be asked to follow a special diet that is low in iodine. This reduces your body’s iodine stores. This will enhance the uptake of radioactive iodine even further; because, without dietary iodine, any remaining normal or thyroid cancer cells will be hungrier for iodine-- making the radioactive iodine treatment more effective. The key to a low-iodine diet is avoiding and limiting dairy products, fish, and iodized salt, which is present in luncheon meats, canned items, and packaged snacks. You will be asked to stop taking multivitamins containing iodine. Several days after your treatment you will resume a regular diet and thyroid medication.
Will I have to be hospitalized? How long will I have to be hospitalized or take precautions around other people and why?
Nuclear Regulatory Commission (NRC) rules enable some states to administer radioactive iodine treatment to most thyroid cancer patients without hospitalization. Nonetheless, many states require hospitalization for those receiving all but the lowest doses of radioactive iodine. If you are hospitalized, you will be discharged after the amount of radioactivity remaining in your body falls below a certain amount determined by the NRC and your state’s radiation safety guidelines. When you leave the hospital, there will still be some radioactivity from the treatment remaining in your body. Most of it will be gone within a few days of leaving the hospital. Virtually all of it will be gone after six weeks.
Although the NRC has no requirements after you are permitted to leave the hospital, it is prudent to keep the exposure of others to a level as low as REASONABLY achievable. Of course, what is reasonable for some families may cause hardship in others, so that common sense should guide you in deciding how closely you can follow the guidelines outlined below. Please remember that children and pregnant women may be especially sensitive to radiation and that you should pay particular attention to minimizing the time spent with them in the first week. Since radioactivity is eliminated in the urine, stool, saliva, and breast milk; exposing others to these should be avoided.
The following are standard sample guidelines to follow after treatment with radioactive iodine. The time recommended may vary under different circumstances:
For at least two days after you leave the hospital or longer if you were treated as an outpatient:
- Minimize the time spent close to people. Except for short encounters, try to maintain a distance greater than five feet from others.
- Drink plenty of fluids.
- Avoid preparing food for others.
- Avoid sharing cigarettes, toothbrushes, or kissing anyone.
- Avoid pregnant women and young children.
For the following week:
Continue to avoid pregnant women and young children.
What are the long and short-term side effects and consequences of radioactive iodine therapy? Can it cause other types of cancer?
The immediate adverse effects of radioactive iodine therapy are usually minimal. Mild nausea or vomiting, which is much less common, may occur during the first few days after the treatment. Some patients develop mild pain in the front of the neck where radioactive iodine is concentrated in the thyroid tissue remaining after surgery. Mild, temporary eye inflammation has been observed. Pain and swelling of the salivary glands may also occur during the first few days after the treatment. Some patients experience a dry mouth, metallic taste, and even a loss of taste. The metallic taste usually resolves within several days. Loss of taste occasionally lasts up to several weeks. On rare occasions, the dry mouth is reported to persist. Some men develop slightly lower sperm counts after the treatment, but the counts usually return to normal. Women may experience a temporary loss of their periods, although this may be the result of becoming hypothyroid rather than a direct effect of radiation. The best way to minimize the side effects from radioactive iodine is to stay well hydrated for several days around the time of therapy. This can be accomplished by having about eight glasses of fluid a day.
In consideration of the amount of harm to a fetus or unborn baby from radioactivity given during pregnancy, you should not have the treatment if there is a possibility that you are pregnant. It is mandatory that pregnancy be ruled out at the time of diagnostic scanning and radioactive iodine therapy. Breast-feeding should be discontinued prior to planning the treatment. Waiting approximately a year before becoming pregnant is recommended. This enables your doctors to determine whether you will need more radioactive iodine, and allows your body to not only eliminate all the radioactive iodine from your body, but also stabilize your thyroid condition and recover from the short-term consequences of radiation.
Repeated treatments with large doses of radioactive iodine have been associated with a very small increase in the incidence of leukemia and other cancers. Treatment schedules are designed to minimize the risk of developing other cancers such as these.
Chemotherapy
Will I get chemotherapy?
Generally, surgery and radioiodine are sufficient for treatment of thyroid cancer. However, chemotherapy may be necessary to treat the less common aggressive forms of thyroid cancer. An example of this type of thyroid cancer is a rare form called anaplastic thyroid cancer. At present, research trials are ongoing to develop effective agents for anaplastic thyroid cancer and other aggressive forms of thyroid cancer.
Follow-up
What type of follow up will I need?
All follow-up is based on the type of thyroid cancer and is specific to the risk of recurrence of the thyroid cancer type and the extent of involvement in the body. In general, after thyroid surgery (except lymphoma and some anaplastic thyroid cancers), your doctor will devise a short-term treatment plan and also outline a preliminary, long-term treatment plan. Daily thyroid hormone therapy will be a mainstay for life when the thyroid gland has been removed. More specific therapies may be needed, such as radioactive iodine or, occasionally, repeat surgery. There are types of specific follow-up blood work (e.g., serum thyroglobulin for monitoring papillary and follicular thyroid cancers; or, serum calcitonin for medullary thyroid cancer) that may be recommended. Other tests may include neck ultrasound and radioactive iodine scanning to look for persistent or recurrent disease. Sometimes a drug called recombinant TSH will be used just before blood sampling for thyroglobulin or just before a radioactive iodine scan. Occasionally, other imaging such as CT scanning or PET scanning will be ordered.
Usually, patients are reevaluated at approximately three month intervals in the first six months and either at six or 12 months thereafter. When surgery and the short-term plan of treatment have documented a stable and safe condition, then a longer time interval may be utilized between patient visits.
When will I know if I am cured and do not have to be followed any more?
Some patients, who have undergone additional testing over 1-4 years with no evidence of residual disease and are declared “cured,” usually have very limited disease which has been totally eradicated by their surgical thyroidectomy or, less commonly, destroyed by follow-up additional treatment such as radioiodine. However, most all patients are advised follow-up and long-term surveillance. Because of the exquisite sensitivity of periodic determinations of serum thyroglobulin (papillary and follicular thyroid cancers), serum calcitonin (medullary cancer) as well as ultrasound imaging for monitoring, some previously designated “cured” patients have been documented years and even decades later with disease persistence and delayed recurrences.
Thank you section authors:
Jeffrey R. Garber, MD, FACE
Thyroid Cancer Webpage Taskforce Chair
Daniel S. Duick, MD, FACP, FACE
Hossein Gharib, MD, MACP, MACE
Thank you to Genzyme for supporting this webpage through an unrestricted educational grant
