Thyroid Cancer

What is thyroid cancer?

Thyroid cancer develops in the thyroid gland, a butterfly-shaped organ located at the base of the neck. The thyroid gland is part of the endocrine system, which is a system of glands that produce hormones which regulate bodily functions, including hormones to regulate body temperature, metabolism, and heart rate.

Thyroid cancer occurs when abnormal cells within the thyroid gland begin to grow uncontrollably resulting in the formation of a malignant tumor. Most thyroid cancers grow at a slow rate and have a favorable prognosis. Thyroid cancer has a high survival rate, particularly when diagnosed and treated in its early stages.

Who is affected by thyroid cancer?

Women are three times more likely than men to get thyroid cancer. It is usually diagnosed in women aged 40 - 60 years old, and in men who are 60 - 80 years old. The disease can also affect younger people and children.

Are there different types of thyroid cancer?

Thyroid cancer is classified on the type of cells from which it grows:

• Papillary: Most cases (approximately 85%) of thyroid cancer are papillary. It is a slow growing form of the disease which can spread to the lymph nodes but responds well to treatment. It is usually curable.
• Follicular: A less common type of thyroid cancer, which is more likely to spread to other organs and the bones. If it has spread, it is more difficult to treat.
• Medullary: A much rarer type of thyroid cancer which is usually found in people with a family history of the disease. Doctors believe it may be caused by a faulty gene.
• Anaplastic: Another much rarer type of thyroid cancer which is aggressive and hard to treat. It grows quickly and often spreads to other parts of the body.

If thyroid cancer is diagnosed, your doctor will stage it to find out whether it has spread. Thyroid cancer usually spreads to the lymph nodes and nearby tissues first, then to other organs, distant lymph nodes and the bones.

What are the signs and symptoms of thyroid cancer?

You or your doctor may notice a lump in your neck. This is called a thyroid nodule – usually, these nodules are not cancerous but should always be assessed by a doctor.

Other symptoms of thyroid cancer include:

• Hoarseness or loss of voice
• Difficulty breathing or swallowing
• Swollen lymph nodes in the neck.

If the thyroid cancer has spread (metastasized) to other parts of the body, symptoms might include:

• Loss of appetite
• Nausea/vomiting
• Tiredness
• Unexplained weight loss.

What causes thyroid cancer?

Doctors don’t know exactly what causes thyroid cancer, but they believe certain factors may increase the risk of it developing:

• A family history of thyroid cancer or other thyroid diseases
• A mutation of the genes that cause certain endocrine diseases
• Being overweight
• Abnormal levels of iodine in the body
• Previous exposure to radiation (for treatment of cancers of the head and neck).

How is thyroid cancer diagnosed?

After performing a physical examination, your doctor may perform the following tests:

• Blood tests: To check for hormone levels and to see if the thyroid is working properly.
• Ultrasound: A non-invasive imaging technique, using high-frequency sound waves to create detailed images of the thyroid gland, which can aid in assessing the size, structure, and any abnormalities of the thyroid.
• Biopsy: Using a needle, a small sample of cells are taken from the thyroid gland and tested for cancer cells.
• Radioiodine scan: A pill containing radioactive iodine (radioiodine) is swallowed, which is absorbed by the thyroid gland. A device is used which measures the amount of radioiodine in the thyroid gland – areas with less radiation are tested further to see if cancer is present.
• Imaging scans: CT (computed tomography) and PET (positron emission tomography) scans can detect thyroid cancer and show whether it has spread.

How is thyroid cancer treated?

The treatment given for thyroid cancer will depend on the size of the tumor and whether it has spread. Treatment may include:

• Surgery: The primary treatment for thyroid cancer, a surgeon will remove some or all of the gland (depending on its size and location). The nearby lymph nodes may also be removed if the cancer has spread.
• Radioiodine therapy: Using a higher dose of radioactive iodine (compared to the diagnostic test), a pill is swallowed, and the radioiodine shrinks the diseased thyroid gland and kills the cancer cells.
• Radiation therapy: Radiation delivers strong beams of energy to the cancer cells and kills them. Radiation may be delivered internally or externally.

If the thyroid cancer is advanced or has returned (recurrent), additional treatments may be given:

• Chemotherapy: Medication is given intravenously or orally which kills cancer cells and its growth.
• Hormone therapy: Medication blocks the release of hormones which can cause cancer to spread or return.
• Protein-kinase inhibitors: Medication is given which kills the cancerous cells and stops the cancer from growing.
• Immunotherapy: A type of cancer treatment which uses the body’s own immune system to fight and kill cancer cells.

To learn more about the treatment of thyroid cancer, click here.

The earlier thyroid cancer is diagnosed, the less chance it has of spreading to other parts of the body. Thyroid cancer may return, but it is a slow-growing form of the disease so often takes many years. Following treatment for thyroid cancer, thyroid hormones need to be taken long-term to allow the body to function.

Can thyroid cancer be prevented?

As the exact cause of thyroid cancer isn’t known, it isn’t possible to prevent it. However, if you are known to be at risk (see above), taking certain steps may help to reduce the likelihood of it developing:

• Preventive surgery: Called prophylactic surgery, this is offered to people who have taken a genetic test which has confirmed that they have a gene mutation which increases their risk of developing medullary thyroid cancer.
• Potassium iodide: If you have been exposed to radiation, taking potassium iodide can lower the risk of developing thyroid cancer. The potassium iodide must be taken within 24 hours of exposure. It works by stopping the thyroid gland from absorbing radioiodine.