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Cancer Treatments
Thyroid Cancer
Thyroid cancer develops in your thyroid, a butterfly-shaped gland located at the base of your neck, just below your Adam's apple. Although your thyroid gland is small, it produces hormones that regulate every aspect of your metabolism, from your heart rate to how quickly you burn calories.
Sometimes you may develop one or more solid or fluid-filled lumps called nodules in your thyroid. Most of these are noncancerous (benign) and cause no symptoms. But a small percentage are cancerous (malignant). Serious complications are possible in thyroid cancer.
The prognosis is often excellent for thyroid cancer. The most common types of thyroid cancer can often be completely removed with surgery. But the important first step is to know the symptoms of thyroid cancer and see your doctor.
Signs and Symptoms
Most often, you won't have signs and symptoms in the early stages of thyroid cancer. But, as the cancer grows, you may experience one or more of the following thyroid cancer symptoms:
- A lump — sometimes growing rapidly — in the front of your neck, just below your Adam's apple
- Hoarseness or difficulty swallowing
- Trouble breathing
- Swollen lymph nodes, especially in your neck
- Pain in your throat or neck, sometimes spreading up to your ears
Having one or more of these symptoms doesn't mean you have thyroid cancer. Other conditions — including a benign thyroid nodule, an infection or inflammation of the thyroid gland, and a benign enlargement of the thyroid (goiter) — can cause similar problems, all of which are highly treatable.
Causes
Your thyroid gland is composed of two lobes that resemble the wings of a butterfly separated by a thin section of tissue called the isthmus. The thyroid takes up iodine from the food you eat and uses it to manufacture two main hormones, thyroxine (T-4) and triiodothyronine (T-3). These hormones maintain the rate at which your body uses fats and carbohydrates, help control your body temperature, influence your heart rate and regulate the production of protein. Your thyroid gland also produces calcitonin, a hormone that regulates the amount of calcium in your blood.
The thyroid contains two main types of cells. Follicle cells make the thyroid protein thyroglobulin and produce and store thyroxine and triiodothyronine. Other cells, called C cells (parafollicular cells), produce calcitonin. The distinction is important because each type can give rise to different types of cancer.
Papillary and follicular cancers develop in follicle cells. They account for the great majority of thyroid cancers, can usually be completely removed with surgery and generally result in an excellent prognosis. Medullary cancer, on the other hand, arises in the thyroid's C cells and is generally more aggressive and harder to treat than papillary and follicular cancers are.
What Causes Thyroid Cancer?
Healthy cells grow and divide in an orderly way. This process is controlled by DNA — the genetic material that contains the instructions for every chemical process in your body. When DNA is damaged or altered, changes occur in these instructions. One result is that cells may begin to grow out of control and eventually form a tumor — a mass of malignant cells.
In the case of thyroid cancer, DNA damage can occur from exposure to environmental contaminants such as radiation, from the aging process or, in medullary cancers, from genetic causes:
Radiation. If you've been exposed to radiation, you have a greater risk of thyroid cancer, but it may not appear for decades after exposure. Children who received high doses of radiation to treat conditions such as acne, enlarged tonsils and scalp infections between the 1920s and 1950s are at higher risk of thyroid cancer and thyroid nodules than are those who didn't receive these treatments. Also at high risk of thyroid cancer are people who have been exposed to radioactive particles from atomic weapons tests and nuclear power plant accidents such as the 1986 Chernobyl disaster in the former Soviet Union.
The greatest cancer risk comes from a component of fallout called iodine 131, a radioactive isotope of naturally occurring iodine that concentrates in the thyroid gland. Iodine 131 is especially harmful to children, whose thyroid glands are still developing.
Genetic causes. Familial medullary cancer and MEN 2 medullary thyroid cancer result from a genetic defect — a mutation of a gene that controls cell growth (oncogene) called RET. The mutation is inherited, and each child of a parent with the defect has a 50 percent chance of inheriting it as well. Before the discovery of the RET gene, people with a family history of medullary thyroid cancer were screened using tests that measure levels of calcitonin and carcinoembryonic antigen. Now, genetic testing allows doctors to discover an inherited tendency to thyroid cancer much earlier — before symptoms or abnormal blood tests ever develop.
Risk factors
Although the exact cause of many cases of thyroid cancer isn't known, certain factors increase your risk:
Exposure to radiation. This includes radiation you may have received as a treatment for acne or other childhood diseases as well as radiation from nuclear fallout. If you're concerned about possible radiation exposure, talk to your doctor. Or contact the National Cancer Institute's Cancer Information Service at (800) 4-CANCER , or (800) 422-6237 , for more information.
Family history. Having a parent with MEN 2A, MEN 2B or familial medullary cancer means you have a 50 percent chance of having the genetic mutation that causes these diseases. If you have one of these types of cancer yourself, your children have a 50 percent chance of developing cancer. Your doctor or a genetic counselor can give you more information and answer any questions you may have regarding genetic screening and treatment. Certain inherited conditions. Your risk of papillary thyroid cancer increases if you have Gardner's syndrome or familial adenomatous polyposis — genetic disorders in which large numbers of precancerous polyps develop throughout your colon and upper intestine. Untreated, Gardner's syndrome and familial adenomatous polyposis usually lead to colon cancer. Having Cowden disease, a rare, inherited disorder that causes lesions on your face, hands and feet, and inside your mouth, also increases your risk of developing thyroid cancer and breast cancer. Your sex. For reasons that aren't clear, women are two to three times as likely as men to develop thyroid cancer.
Reproductive history. Women whose last pregnancy occurs at age 30 or later appear to be at higher risk of thyroid cancer than are women who have children earlier in life.
Age. Papillary and follicular thyroid cancers can develop at any age but are more common in young adulthood. Sporadic medullary thyroid cancer usually occurs in adults. MEN 2 and familial medullary cancer also occur in adults but can affect children and infants as well.
Race. White Americans are more likely to develop thyroid cancer than black Americans are.
When to Seek Medical Advice
See your doctor if you develop any of the symptoms of thyroid cancer, including a lump in your neck near your Adam's apple, hoarseness, or trouble swallowing or breathing. And don't hesitate to talk to your doctor if you think you may be at risk of thyroid problems or are worried about radiation treatments you received in childhood.
Screening and Diagnosis
Although it's possible that you may see or feel a lump (nodule) in your thyroid yourself — usually just to the lower right or left of your Adam's apple — it's more likely that your doctor will discover a lump during a routine medical exam. You're usually asked to swallow while your doctor examines your thyroid because the thyroid moves up and down during swallowing, making nodules easier to feel.
Sometimes a thyroid nodule is detected as an incidental finding when you have an imaging test to evaluate another condition in your head or neck. Nodules detected this way are usually too small to be found during a physical exam.
To aid in diagnosis, you may have one or more of the following tests:
Ultrasound scan. This imaging technique uses high-frequency sound waves to outline the neck anatomy and detect abnormal growths. While very good at identifying whether a growth or nodule is present, ultrasound scans can't tell for sure whether it's malignant or benign. Ultrasound is safe, with virtually no complications associated with its use.
Fine-needle aspiration (FNA) biopsy. This test is generally considered the most sensitive for distinguishing between benign and malignant thyroid nodules.
During the procedure, your doctor places a thin needle through your skin and into a nodule and removes a sample of cells. Several passes are usually needed to obtain tissue from different parts of the nodule. If you have more than one nodule, your doctor is likely to take samples from as many as possible. Often, your doctor will use ultrasound to help guide the placement of the needle. The samples are then sent to a laboratory and analyzed under a microscope.
Only a small percentage of biopsied nodules are malignant. This diagnosis is based on the characteristics of individual cells and patterns in clusters of cells that are different from normal thyroid tissue. In some cases, a pathologist can determine specific types of cancer from an FNA biopsy sample.
Blood tests. If your doctor suspects medullary cancer, you may have tests that check for high levels of calcitonin in your blood. Other tests can provide information about the function of your thyroid gland. For example, you may have a test that measures thyroid-stimulating hormone (TSH), a hormone made by the pituitary gland that regulates thyroid hormones.
Treatment
Thyroid cancer treatment generally includes one or more of the following:
Surgery
Surgery is the main type of treatment for thyroid cancer. Most surgeons use a procedure called near-total thyroidectomy — an operation that removes practically the entire thyroid with the exception of small rims of tissue around the parathyroid glands to reduce the risk of parathyroid damage. If you have enlarged lymph nodes as a result of thyroid cancer, your operation may be extended to remove the affected lymph nodes.
Cancer is less likely to return or spread after thyroidectomy than after less complete operations, and in experienced hands, the risks of the surgery are low. The greatest risk associated with the operation is unintended nerve injury. Such injury could cause permanent damage to your voice, but this occurs rarely. Another potential risk is damage to the parathyroid glands, resulting in low calcium levels.
In some cases, the type of cancer can't be diagnosed until the affected tissue is examined. Sometimes, this can be done during surgery using a technique called frozen section, which takes less than 10 minutes to complete and which is performed while you're still anesthetized. When this procedure isn't available, surgeons are likely to remove the lobe of the thyroid that contains the nodule (lobectomy) and send it to a pathologist, who examines it under a microscope. If the nodule is malignant, the next step is near-total thyroidectomy.
Thyroid hormone therapy
After any type of surgery for thyroid cancer, you'll need to take the thyroid hormone medication levothyroxine (Levothroid, Synthroid, others) for life. This has two benefits: It supplies the missing hormone your thyroid would normally produce, and it suppresses the pituitary's production of TSH, which signals your thyroid to manufacture hormones. High TSH levels could conceivably stimulate any remaining cancer cells to grow.
You'll likely have blood tests to check your thyroid hormone levels every few months until your doctor finds the proper dosage for you. Too much hormone can cause unintended weight loss, palpitations, tremors, osteoporosis and frequent bowel movements. Too little may lead to weight gain, sensitivity to cold, and dry skin and hair.
Radioactive iodine (radioiodine) follow-up screening and therapy
After surgery, radioiodine may be used in small doses for a follow-up test called a thyroid scan. During the test, a radioactive isotope is injected into the vein on the inside of your elbow. You then lie on a table while a special camera produces an image of your thyroid on a computer screen. The scan can detect any remaining normal thyroid tissue. A thyroid scan also may detect thyroid cancer cells that have spread and that could not be identified at the time of surgery or on other imaging, both in the neck and in other parts of your body.
If any normal tissue remains, moderate doses of radioiodine can be used to eliminate the normal tissue (remnant ablation). Larger doses can be used to destroy any cancerous cells that have spread beyond the thyroid gland. Because radioiodine is taken up primarily by thyroid tissue — including thyroid cancer cells — other parts of your body are less affected. Normal thyroid tissue must be removed first because it absorbs more iodine than do cancer cells, and its presence would make the treatment against cancer cells less effective.
With radioiodine therapy, you take a capsule containing iodine 131. Before you undergo radioiodine therapy, you need high blood levels of TSH in order for cancer cells to take up radioactive iodine. For that reason, you normally discontinue taking thyroid hormones for up to two weeks before therapy or your doctor may recommend a synthetic version of a hormone that artificially elevates blood levels of TSH.
Radioactive iodine therapy is typically administered about six weeks after surgery, generally as an outpatient procedure. Higher doses of this treatment may require hospitalization for two or three days.
You may have a sore throat, nausea and vomiting immediately after radioiodine treatment. You may also have a dry mouth or pain in your cheeks and neck because your salivary glands may absorb some of the radioactive iodine. And because iodine 131 can affect the thyroid gland of a developing fetus or infant, you shouldn't have radioiodine therapy if you're pregnant or breastfeeding.
Radioiodine treatments aren't an option for people with medullary cancer because thyroid C cells don't absorb iodine.
External beam radiation
Like radioiodine therapy, external beam radiation uses radioactivity to destroy cancer cells. But in this case, the rays come from a source outside your body — a high-energy X-ray machine called a linear accelerator. The cancer cells are targeted with a high dose of radiation for a few minutes at a time, usually five days a week, over the course of six to eight weeks. The goal is to destroy the cancer cells while minimizing damage to healthy tissue. You're likely to feel very tired later in the course of treatment, and your skin may become red and tender in the treated area, as if you had a bad sunburn. You may also feel hoarse or have trouble swallowing.
Chemotherapy
Chemotherapy, the use of drugs to kill cancer cells that have spread to other parts of the body, may be used in some cases, such as for medullary thyroid cancer, which doesn't respond to radioiodine therapy. Not every person with medullary thyroid cancer responds to chemotherapy, but in some cases a combination of cancer drugs may shrink tumors or slow their growth.
Chemotherapy may also be used for anaplastic thyroid cancer, the most aggressive and fastest growing type of thyroid cancer. Anaplastic cancer often can't be helped by surgery by the time it's diagnosed. Radiation or chemotherapy may shrink tumors slightly and make you more comfortable.