Thyroid cancer: whos at risk?
No one knows the exact causes of thyroid cancer. Doctors can seldom explain why one person gets this disease and another does not. However, it is clear that thyroid cancer is not contagious. No one can catch cancer from another person.
Research has shown that people with certain risk factors are more likely than others to develop thyroid cancer. A risk factor is anything that increases a persons chance of developing a disease.
The following risk factors are associated with an increased chance of developing thyroid cancer:
No one knows the exact causes of
thyroid cancer.
Thyroid cancer is not contagious.
No one can catch cancer from
another person.
Radiation: People exposed to high levels of radiation are much more likely than others to develop papillary or follicular thyroid cancer.
One important source of radiation exposure is treatment with x-rays. Between the 1920s and the 1950s, doctors used high-dose x-rays to treat children who had enlarged tonsils, acne, and other problems affecting the head and neck. Later, scientists found that some people who had received this kind of treatment developed thyroid cancer.
(Routine diagnostic x-rays-such as dental x-rays or chest x-rays-use very small doses of radiation. Their benefits nearly always outweigh their risks. However, repeated exposure could be harmful, so it is a good idea for people to talk with their dentist and doctor about the need for each x-ray and to ask about the use of shields to protect other parts of the body.)
Another source of radiation is radioactive fallout. This includes fallout from atomic weapons testing (such as the testing in the United States and elsewhere in the world, mainly in the 1950s and 1960s), nuclear power plant accidents (such as the Chornobyl [also called Chernobyl] accident in 1986), and releases from atomic weapons production plants (such as the Hanford facility in Washington state in the late 1940s). Such radioactive fallout contains radioactive iodine (I-131). People who were exposed to one or more sources of I-131, especially if they were children at the time of their exposure, may have an increased risk for thyroid diseases.
People who are concerned about their exposure to radiation from medical treatments or radioactive fallout may wish to ask the Cancer Information Service at 1-800-4-CANCER about additional sources of information.
Family history: Medullary thyroid cancer can be caused by a change, or alteration, in a gene called RET. The altered RET gene can be passed from parent to child. Nearly everyone with the altered RET gene will develop medullary thyroid cancer. A blood test can detect an altered RET gene. If the abnormal gene is found in a person with medullary thyroid cancer, the doctor may suggest that family members be tested. For those found to carry the altered RET gene, the doctor may recommend frequent lab tests or surgery to remove the thyroid before cancer develops. When medullary thyroid cancer runs in a family, the doctor may call this familial medullary thyroid cancer or multiple endocrine neoplasia (MEN) syndrome. People with the MEN syndrome tend to develop certain other types of cancer.
A small number of people with a family history of goiter or certain precancerous polyps in the colon are at risk for developing papillary thyroid cancer.
Being female: In the United States, women are two to three times more likely than men to develop thyroid cancer.
Age.: Most patients with thyroid cancer are more than 40 years old. People with anaplastic thyroid cancer are usually more than 65 years old.
Race: In the United States, white people are more likely than African Americans to be diagnosed with thyroid cancer.
Not enough iodine in the diet. The thyroid needs iodine to make thyroid hormone. In the United States, iodine is added to salt to protect people from thyroid problems. Thyroid cancer seems to be less common in the United States than in countries where iodine is not part of the diet.
Most people who have known risk factors do not get thyroid cancer. On the other hand, many who do get the disease have none of these risk factors. People who think they may be at risk for thyroid cancer should discuss this concern with their doctor. The doctor may suggest ways to reduce the risk and can plan an appropriate schedule for checkups.
Symptoms
Early thyroid cancer often does not cause symptoms. But as the cancer grows, symptoms may include:
A lump, or nodule, in the front of the neck near the Adams apple;
Hoarseness or difficulty speaking in a normal voice;
Swollen lymph nodes, especially in the neck;
Difficulty swallowing or breathing; or
Pain in the throat or neck.
These symptoms are not sure signs of thyroid cancer. An infection, a benign goiter, or another problem also could cause these symptoms. Anyone with these symptoms should see a doctor as soon as possible. Only a doctor can diagnose and treat the problem.
Diagnosis
If a person has symptoms that suggest thyroid cancer, the doctor may perform a physical exam and ask about the patients personal and family medical history. The doctor also may order laboratory tests and imaging tests to produce pictures of the thyroid and other areas.
The exams and tests may include the following:
Physical exam- The doctor will feel the neck, thyroid, voice box, and lymph nodes in the neck for unusual growths (nodules) or swelling.
Blood tests- The doctor may test for abnormal levels (too low or too high) of thyroid-stimulating hormone (TSH) in the blood. TSH is made by the pituitary gland in the brain. It stimulates the release of thyroid hormone. TSH also controls how fast thyroid follicular cells grow.
If medullary thyroid cancer is suspected, the doctor may check for abnormally high levels of calcium in the blood. The doctor also may order blood tests to detect an altered RET gene or to look for a high level of calcitonin.
Ultrasonography- The ultrasound device uses sound waves that people cannot hear. The waves bounce off the thyroid, and a computer uses the echoes to create a picture called a sonogram. From the picture, the doctor can see how many nodules are present, how big they are, and whether they are solid or filled with fluid.
Radionuclide scanning- The doctor may order a nuclear medicine scan that uses a very small amount of radioactive material to make thyroid nodules show up on a picture. Nodules that absorb less radioactive material than the surrounding thyroid tissue are called cold nodules. Cold nodules may be benign or malignant. Hot nodules take up more radioactive material than surrounding thyroid tissue and are usually benign.
Biopsy- The removal of tissue to look for cancer cells is called a biopsy. A biopsy can show cancer, tissue changes that may lead to cancer, and other conditions. A biopsy is the only sure way to know whether a nodule is cancerous.
The doctor may remove tissue through a needle or during surgery:
Fine-needle aspiration: For most patients, the doctor removes a sample of tissue from a thyroid nodule with a thin needle. A pathologist looks at the cells under a microscope to check for cancer. Sometimes, the doctor uses an ultrasound device to guide the needle through the nodule.
Surgical biopsy: If a diagnosis cannot be made from the fine-needle aspiration, the doctor may operate to remove the nodule. A pathologist then checks the tissue for cancer cells.
A person who needs a biopsy may want to ask the doctor the following questions:
What kind of biopsy will I have?
How long will the procedure take? Will I be awake? Will it hurt?
Will I have a scar on my neck after the biopsy?
How soon will you have the results? Who will explain them to me?
If I do have cancer, who will talk to me about treatment? When?
Staging
If the diagnosis is thyroid cancer, the doctor needs to know the stage, or extent, of the disease to plan the best treatment. Staging is a careful attempt to learn whether the cancer has spread and, if so, to what parts of the body.
The doctor may use ultrasonography, magnetic resonance imaging (MRI), or computed tomography (CT) to find out whether the cancer has spread to the lymph nodes or other areas within the neck. The doctor may use a nuclear medicine scan of the entire body, such as a radionuclide scan known as the diagnostic I-131 whole body scan, or other imaging tests to learn whether thyroid cancer has spread to distant sites.
Treatment
People with thyroid cancer often want to take an active part in making decisions about their medical care. They want to learn all they can about their disease and their treatment choices. However, the shock and stress that people may feel after a diagnosis of cancer can make it hard for them to think of everything they want to ask the doctor. It often helps to make a list of questions before an appointment. To help remember what the doctor says, patients may take notes or ask whether they may use a tape recorder. Some also want to have a family member or friend with them when they talk to the doctor-to take part in the discussion, to take notes, or just to listen.
The doctor may refer patients to doctors (oncologists) who specialize in treating cancer, or patients may ask for a referral. Specialists who treat thyroid cancer include surgeons, endocrinologists (some of whom are called thyroidologists because they specialize in thyroid diseases), medical oncologists, and radiation oncologists.
Treatment generally begins within a few weeks after the diagnosis. There will be time for patients to talk with the doctor about treatment choices, get a second opinion, and learn more about thyroid cancer.
Getting a Second Opinion
Before starting treatment, the patient might want a second opinion about the diagnosis and the treatment plan. Some insurance companies require a second opinion; others may cover a second opinion if the patient or doctor requests it. Gathering medical records and arranging to see another doctor may take a little time. In most cases, a brief delay does not make treatment less effective.
Compiled by M. Akhteruzzaman MD, New York, USA
