Thyroid Cancer

What is the thyroid gland?

The thyroid is a small gland in the neck and it is made of two lobes or parts, shaped like a butterfly. The thyroid cannot usually be felt in the neck if it is normal.

The thyroid gland contains follicular cells which produce the two main hormones, thyroxine (T4) and triiodothyronine (T3), which are needed to keep the body functioning at its normal rate. These hormones affect the heart rate, body temperature and energy level. The thyroid gland also contains C cells which make calcitonin, a hormone that helps control the level of calcium in the blood.

What is cancer?

Cancer is a disease of the cells in the body. The body is made up from millions of tiny cells. There are many different types of cell in the body, and there are many different types of cancer which arise from different types of cell. What all types of cancer have in common is that the cancer cells are abnormal and multiply 'out of control'.

A malignant tumour is a 'lump' or 'growth' of tissue made up from cancer cells which continue to multiply. Malignant tumours invade into nearby tissues and organs which can cause damage.

Malignant tumours may also spread to other parts of the body. This happens if some cells break off from the first (primary) tumour and are carried in the bloodstream or lymph channels to other parts of the body. These small groups of cells may then multiply to form 'secondary' tumours (metastases) in one or more parts of the body. These secondary tumours may then grow, invade and damage nearby tissues, and spread again.

Some cancers are more serious than others, some are more easily treated than others (particularly if diagnosed at an early stage), some have a better outlook (prognosis) than others.

So, cancer is not just one condition. In each case it is important to know exactly what type of cancer has developed, how large it has become, and whether it has spread. This will enable you to get reliable information on treatment options and outlook. See separate leaflet called 'Cancer - What are Cancer and Tumours?' for further details about cancer in general.

What is thyroid cancer?

There are four main types of thyroid cancer:

• Papillary. This is the most common type of thyroid cancer.
• Follicular. This is a less common type of thyroid cancer, usually found in older people. Both papillary and follicular thyroid cancers are sometimes called differentiated thyroid cancer. They are slow growing and are often treated in the same way.
• Medullary. This is a rare type of thyroid cancer that can run in families. For this reason, members of your family may be checked at regular intervals to ensure they are not showing any signs of the cancer. This grows from the C cells in the thyroid gland.
• Anaplastic. This is also a rare type of thyroid cancer. It occurs more commonly in older people and grows quickly. Unlike other types of thyroid cancer, it can be difficult to treat.

The other types of cancer that can develop in the thyroid gland are lymphoma and Hurthle cell cancer. These will not be discussed in this article.

Papillary and follicular thyroid cancers account for 80-90% of all thyroid cancers. Both types begin in the follicular cells of the thyroid. Most papillary and follicular thyroid cancers tend to grow slowly. If they are detected early, most can be treated successfully.

What causes thyroid cancer?

A cancerous tumour starts from one abnormal cell. The exact reason why a cell becomes cancerous is unclear. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply 'out of control'. (See separate leaflet called 'Cancer - What Causes Cancer' for more details.)

Thyroid cancer is uncommon. Around 1,750 people develop it each year in the UK. Women are more commonly affected than men. Although most people develop thyroid cancer when they are middle-aged or older, papillary cancer of the thyroid can affect younger women, most commonly between 35 and 40 years.

Many people develop thyroid cancer for no apparent reason. However, certain risk factors increase the chance that thyroid cancer may develop. These include:

• Thyroid diseases. People who have some non-cancerous (benign) thyroid diseases are more likely to develop thyroid cancer, for example a goitre (enlarged thyroid), thyroid nodules (adenomas) or inflammation of the thyroid (thyroiditis). Note: having hypothyroidism or hyperthyroidism does not increase your risk of developing thyroid cancer.
• Previous radiation. Thyroid cancer is more common in people who had radiotherapy treatment to the neck area at a young age.
• Family history. Medullary thyroid cancer can be caused by inheriting abnormal genes. Around one in four people who develop medullary thyroid cancer have an abnormal gene.
• Low iodine levels. However, it is very rare for people in the UK to have low iodine levels but they can sometimes be caused by radiation exposure in the past.

What are the symptoms of thyroid cancer?

Cancer of the thyroid usually develops very slowly and initially does not cause any symptoms. The most common sign is a small lump in the neck which is painless.

Other symptoms which may develop as the cancer grows include:

• Hoarseness or difficulty in speaking in a normal voice.
• Swollen lymph glands in the neck.
• Difficulty swallowing or breathing as the cancer presses on the oesophagus (gullet) or windpipe.
• Pain in the throat or neck.

Note: most lumps in the thyroid gland are not due to cancer. Only about 1 in 20 thyroid lumps are due to cancer.

How is thyroid cancer diagnosed and assessed?

Tests to confirm the diagnosis

An ultrasound may also be used to assess the size and position of the cancer. This is a safe and painless test which uses sound waves to create images of organs and structures inside your body.

A biopsy is usually performed to confirm the cancer and also to find out the type of thyroid cancer you have. A small needle is passed gently into the swelling in your neck. Sometimes the doctor will use an ultrasound scanner to help guide the needle to the right area. The cells are examined under a microscope. The cells look different, depending on the type of cancer you have.

Another test that is sometimes performed is a thyroid radioisotope scan. This test involves having an injection of a small amount of a slightly radioactive liquid (technetium or iodine) and then a scan is performed. Cancer cells do not usually absorb the radioactive liquid as well as normal thyroid cells, so any areas of cancer in the thyroid may be seen.

Assessing the extent and spread

If you are found to have a thyroid cancer, then other tests are likely to be advised. These may include one or more of: a CT or MRI scan, blood tests, a thyroid radioisotope scan and sometimes other tests. (See separate leaflets which describe most of these tests in more detail.)

Finding out the type of the cancer helps doctors to advise on the best treatment options. It also gives a reasonable indication of outlook (prognosis). (See separate leaflet called 'Cancer - Staging and Grading Cancer' for more details.)

What are the treatment options for thyroid cancer?

Treatment options which may be considered include surgery, radioactive iodine and radiotherapy. More than one type of treatment may be given. Most types of thyroid cancer can usually be treated very successfully and many people with thyroid cancer are cured.

You should have a full discussion with a specialist who knows your case. They will be able to give the pros and cons, likely success rate, possible side-effects, and other details about the various possible treatment options for your type of cancer.

You should also discuss with your specialist the aims of treatment. For example:

• In some cases, the treatment aims to cure the cancer. Some thyroid cancers can be cured, particularly if they are treated in the early stages of the disease. (Doctors tend to use the word 'remission' rather than the word 'cured'. Remission means there is no evidence of cancer following treatment. If you are 'in remission', you may be cured. However, in some cases a cancer returns months or years later. This is why doctors are sometimes reluctant to use the word cured.)
• In some cases, the treatment aims to control the cancer. If a cure is not realistic, with treatment it is often possible to limit the growth or spread of the cancer so that it progresses less rapidly. This may keep you free of symptoms for some time.
• In some cases, treatment aims to ease symptoms. For example, if a cancer is advanced then you may require treatments such as painkillers or other treatments to help keep you free of pain or other symptoms. Some treatments may be used to reduce the size of a cancer which may ease symptoms such as pain.

Surgery

An operation to remove all (or sometimes part) of the thyroid gland is the most common treatment. Sometimes the surgeon also removes some, or all, of the lymph nodes close to the thyroid gland, to see whether the cancer has spread into them. This can help to reduce the risk of the cancer coming back after surgery. If the cancer is at an early stage and not spread then surgery alone may be curative.

After your operation, it is likely you will need to take thyroid hormones to replace those normally produced by the thyroid gland.

Radioactive iodine treatment

Many people are given radioactive iodine treatment after their thyroid surgery. Radioactive iodine treatment uses radioactive iodine (I-131) to destroy thyroid cancer cells anywhere in the body. This treatment is usually is given as liquid or capsules. The thyroid cancer cells absorb the iodine and receive a very high dose of radiation, which will help to destroy them. As other cells in the body do not absorb iodine, they are not affected by the radioactive iodine. Most radiation is gone from your body in a few days.

If you have medullary thyroid cancer or anaplastic thyroid cancer then it is unlikely you will receive radioactive iodine treatment as these types of thyroid cancer rarely respond to it.

Radiotherapy

Radiotherapy is a treatment which uses high energy beams of radiation which are focused on cancerous tissue. This kills cancer cells, or stops cancer cells from multiplying. (See separate leaflet called 'Radiotherapy' for more details.) Radiotherapy may be advised if you have thyroid cancer that does not respond to radioactive iodine treatment.

Chemotherapy

Chemotherapy is a treatment of cancer by using anti-cancer drugs which kill cancer cells, or stop them from multiplying. See separate leaflet called 'Chemotherapy' for more details.

Chemotherapy is rarely used to treat cancer of the thyroid but may be used if the cancer returns or has spread to other parts of the body.

Follow up after treatment

After your treatment for thyroid cancer, you will be followed up by your specialist and have regular checkup and tests.

You may have a blood test for thyroglobulin performed at regular intervals. Thyroglobulin is a protein that is usually only made by the healthy thyroid gland, but it can also be produced by papillary or follicular thyroid cancer cells. Measuring thyroglobulin levels is a way of detecting any remaining papillary or follicular cancer cells.

In addition, you may also have radioactive iodine scans from time to time, to ensure there are no thyroid cancer cells in your body.

What is the prognosis (outlook)?

The outlook for people with thyroid cancer is very good. People with papillary or follicular thyroid cancer have an excellent chance of cure with treatment.

The treatment of cancer is a developing area of medicine. New treatments continue to be developed and the information on outlook above is very general. The specialist who knows your case can give more accurate information about your particular outlook, and how well your type and stage of cancer is likely to respond to treatment.

Further help and information

Macmillan Cancer Support

3 Bath Place, Rivington Street, London, EC2A 3JR
Tel: 0808 800 1234 Web: www.cancerbackup.org.uk
Cancerbackup has merged with Macmillan. They provide information and support to anyone affected by cancer.

British Thyroid Foundation

Tel: 01423 709 707 and 01423 709 448 Web: www.btf-thyroid.org
The British Thyroid Foundation (BTF) provides support and information to people with thyroid cancer.

Butterfly Thyroid Cancer Trust

Tel:01207 545469 Web:www.butterfly.org.uk
Butterfly Thyroid Cancer Trust (formerly Butterfly North East) is the first registered charity in the UK dedicated solely to the support of patients with Thyroid Cancer.

Cancer Research UK

Their website www.cancerhelp.org.uk provides facts about cancer including treatment choices.

Other support groups

See www.patient.co.uk/selfhelp.asp for a list of self help and support groups for cancer patients.