This information has been prepared to help you understand more about thyroid cancer. Many people feel understandably shocked and upset when they are told they have thyroid cancer. This information is intended to help you understand the diagnosis and treatment of this type of cancer. We cannot advise you about the best treatment for you. You need to discuss this with your doctors. However, we hope this information will answer some of your questions and help you think about the questions you want to ask your doctors or other health carers.
The thyroid is a butterfly-shaped gland in the front of the neck. It is found below the voice box (larynx or Adam’s apple) and is made up of two halves, called lobes, which lie on either side of the windpipe (trachea). The lobes are connected in the middle by a small band of thyroid tissue known as the isthmus.
The thyroid gland is part of the endocrine system, which consists of a collection of glands responsible for producing the body’s hormones. The thyroid gland makes hormones that help control the speed of the body’s processes, such as heart rate, blood pressure, body temperature and weight – this is known as your metabolic rate.
The three hormones released by the thyroid are:
- Thyroxine (T4): One of the hormones that regulates the body’s metabolism. T4 is converted into another hormone, called T3.
- Tri-iodothyronine (T3): The second type of hormone that controls metabolism. The thyroid produces only small amounts of T3 – the majority of this hormone is created when the body converts T4 into T3. T3 is the active form of the thyroid hormone.
- Calcitonin: A hormone that plays a role in regulating calcium levels in the body.
The thyroid uses iodine (which is present in foods or mineral supplements) to create T4 and T3.
The thyroid gland is made up of two main types of cells, which give rise to different types of thyroid cancer:
- follicular cells make a protein called thyroglobulin, and produce and store T3 and T4
- parafollicular cells (C-cells) produce calcitonin.
Behind the thyroid glands are the parathyroid glands. These four glands produce hormones that control the amount of calcium and phosphorus in the blood.
What is thyroid cancer?
Thyroid cancer occurs when the cells of the thyroid gland grow and divide in a disorderly way.
Types of thyroid cancer
There are four main types of thyroid cancer:
Papillary thyroid cancer – this is the most common type — about 70% of all cases. It develops from the follicular cells, usually forms a tumour on one lobe. Papillary thyroid cancer tends to grow slowly.
Follicular thyroid cancer – second most common type — about 25% of thyroid cancer cases. It develops from follicular cells.
Medullary thyroid cancer – about 4% of all thyroid cancers. It develops from the C-cells. This cancer can occur sporadically, or it can be linked to an inherited faulty gene.
Anaplastic thyroid cancer – rare form of thyroid cancer — about 1% of cases. It may develop from undiagnosed papillary or follicular thyroid cancer. This cancer usually grows quickly and affects elderly people
How common is it?
There are about 650 new cases of thyroid cancer diagnosed in NSW each year. It accounts for 0.8% of all male cancers and 3.3% of all female cancers.
The median age for males to be diagnosed with thyroid cancer is 50; the age for females is 49.
From 1996 to 2005, the incidence rates of thyroid cancer in NSW rose 40% in males and 84% in females. Medical researchers are investigating why incidence rates of thyroid cancer appear to have increased.
There are several risk factors for developing thyroid cancer. The presence of one or more risk factors does not necessarily mean that you will develop cancer.
- Exposure to radiation – A small number of thyroid cancer cases are due to having radiotherapy treatment as a child, or living in an area with high levels of radiation in the environment.
- Family history – Some people inherit a faulty gene called the RET gene that predispose them to developing thyroid cancer.
- Sex – Women are about three times more likely to develop thyroid cancer than men.
- Benign thyroid diseases – Having a thyroid condition, such as thyroid nodules (adenomas), an enlarged thyroid (goitre) or inflammation of the thyroid (thyroiditis), may increase your chance of developing thyroid cancer. However, having an under- or over-active thyroid (hypothyroidism or hyperthyroidism) does not increase your risk.
- Iodine levels – The thyroid uses iodine to make thyroid hormones. Certain foods contain iodine, such as iodised salt, dairy products, seafood and eggs. Some studies have found a link between iodine intake and thyroid cancer, but this is not yet fully understood.
Thyroid cancer usually develops slowly, without many obvious symptoms. Some thyroid cancers are found incidentally when people have their thyroid removed for other reasons.
The most common symptom is a painless lump in the neck or throat, which may increase in size or press on the trachea or oesophagus, making it difficult to breathe or swallow. You may also experience hoarseness or swollen lymph glands in your neck.
A lump is on the thyroid is called a nodule. In about 90% of cases, a nodule is a symptom of goitre (a benign enlarged thyroid gland) or another condition affecting the head or neck.
A cancerous thyroid usually continues to produce hormones, so an under- or over-active thyroid is not typically a symptom of cancer.
If you notice any of these symptoms, you should see your general practitioner (GP) as soon as possible.
If your doctor suspects you have thyroid cancer, you will have one or more of the following tests. It’s unlikely you will have all of the tests listed in this chapter. Some of these tests can also show if the cancer has spread to other parts of your body.
Your doctor may do a blood test to check the levels of hormones (such as T3 and T4) and thyroid-stimulating hormone (TSH). A cancerous thyroid usually continues to function normally, so a blood test may be used to rule out benign thyroid conditions. A blood test may help diagnose medullary thyroid cancer, which may be indicated by an elevated level of calcitonin. A blood test is also commonly used as a follow-up test, to assess if treatment was effective. Sometimes followed by radioisotope scan.
An ultrasound is a non-invasive, painless scan that uses soundwaves to build up a picture of internal organs. Gel is spread over the neck to conduct the ultrasound. A paddle-shaped device is moved over the area for a few minutes and a picture will be formed on a computer screen. The ultrasound can help the doctor determine if a lump in your thyroid is a solid tumour or fluid-filled cyst. The scan can also show if the lymph nodes in the neck are affected.
If the doctor feels a nodule or sees it during an ultrasound, you may have a biopsy. This is when some thyroid tissue is removed and sent for examination under a microscope. There are two ways of taking a biopsy:
Fine needle aspiration — A needle is inserted into the thyroid (or lump in your neck) and a small tissue sample is removed. You may be given local anaesthesia (pain relief) and an ultrasound may be used to guide the needle
Surgical biopsy — The doctor administers a local or general anaesthetic, makes a small cut into the neck and removes a piece of thyroid tissue. This type of biopsy is unusual. Sometimes tissue is biopsied during a hemi-thyroidectomy procedure.
Sometimes a sadioisotope scan is used as a diagnostic test, usually if blood tests show evidence of an overactive thyroid (hyperthyroidism). Commonly used as a follow-up test after treatment. In this test, a small amount of radioactive liquid (such as iodine or technetium) is injected into a vein in your arm. After about 20 minutes, you will be asked to lie under a machine called a gamma camera. The camera measures the amount of radioactive liquid taken up by the thyroid gland. Cells that don’t take up much radioactive fluid are called “cold” nodules, and cells that take up the fluid may be called hyperfunctioning or ‘hot’ nodules.
The presence of a cold nodule may indicate that you have a benign thyroid condition. Only about 10% of cold nodules are cancerous. Hot nodules can also indicate a benign condition (such as hyperthyroidism). It is extremely rare for a hot nodule to be cancerous. A radioisotope scan is painless and causes few side effects. After a diagnostic scan you will not be radioactive and it is safe for you to be with others. If you have the scan after radioactive iodine treatment, you will be slightly radioactive, and you will need to take some precautions to minimise the risk of exposing other people to radiation.
A CT (computerised tomography) scan uses x-ray beams to form a more detailed picture of the inside of the body. You may have a CT scan if your thyroid is enlarged, so your doctor can make sure your windpipe (trachea) is not compressed. A CT scan is unlikely to be used to diagnose papillary or follicular thyroid cancer.
Before the scan, dye may be injected into one of your veins to help create clearer pictures. This may make you feel flushed or hot for a few minutes and may also leave a strange taste in your mouth. The CT scanner is large and round like a doughnut. You will lie on a table that moves in and out of the scanner. Some people feel afraid of confined spaces (claustrophobic), but the scan usually only takes a few minutes.
The MRI (magnetic resonance imaging) scan uses both magnetism and radio waves to build up detailed cross-sectional pictures of the body. You will lie on a table that slides into a metal cylinder – a large magnet – that is open at both ends.A special dye is injected into your veins before the scan — this makes scan pictures clearer.
Some people find lying in the narrow metal cylinder noisy and confining. Let your health care team know if you are uncomfortable or claustrophobic during the scan. People who have a pacemaker, joint replacement or certain other metallic objects in their body cannot have an MRI due to the potentially damaging effect of the magnet. The MRI scan is painless. It usually takes an hour.
PET (positron emission tomography) scan
The PET (positron emission tomography) scan may be used after a thyroidectomy to work out if the cancer has come back. It’s only used occasionally, if the doctor thinks the cancer needs to be viewed in a different way.
Before the scan, you will be asked not to eat or drink for a period of time (fast). During this scan you will be injected with a small amount of radioactive glucose solution. It takes 30-90 minutes for the solution to flow throughout your body.
Your body will then be scanned for concentrated levels of radioactive glucose. Cancer cells show up brighter on the scan because they take up more of the glucose solution than normal cells. The PET scan is usually done on an outpatient basis, however it takes several hours to prepare for and have the scan.
Staging thyroid cancer
If the results of diagnostic tests detect thyroid cancer, your doctor will assign a stage to describe its size and how far it has spread. Staging the cancer helps your health care team decide what treatment is best for you.
Most cancers follow a general, international staging system called TNM, however some types of thyroid cancer are staged according to a numeric system. This system ranges from stage 1 (small, localised cancer) to stage 4 (cancer that has spread to remote parts of the body). The way thyroid cancer is staged depends on several factors, such as the type of thyroid cancer, your age and your general health.
If you are confused about thyroid cancer staging, ask your doctor or nurse to give you more information. You can also call the Cancer Council Helpline on 13 11 20 for more information.
Prognosis means the expected outcome of a disease. The common types of thyroid cancer (such as papillary and follicular cancer) have a very good long term prognosis, especially if the cancer is confined to the thyroid and has not spread (metastasised). You will need to discuss your prognosis with your doctor, but it is not possible for any doctor to give you a 100% accurate prediction on the course of the illness.
The type of thyroid cancer you have, test results, the rate of tumour growth, how well you respond to treatment are all important factors in assessing your prognosis. Your doctor will also consider your age, fitness and medical history.
Which health professionals will I see?
You will be cared for by a range of health professionals who specialise in different aspects of your treatment. These may include:
- endocrinologist – specialises in diagnosing and treating disorders of the endocrine system.
- endocrine surgeon – operates on the thyroid gland, parathyroid glands, adrenal glands and the endocrine pancreas.
- ENT surgeon – specialises in treating the ears, nose and throat, and checks your vocal cords before and after surgery.
- head and neck surgeon – operates on cancer in the head and neck region
- medical oncologist – plans and administers chemotherapy.
- radiation oncologist – plans and administers radiotherapy.
- cancer nurse coordinator – supports you throughout treatment and answers your questions.
- nuclear medicine specialist – coordinates the delivery of radioactive iodine treatment and nuclear scans.
- psychologists and counsellors – help you manage your feelings and cope with changes to your life as a result of cancer or its treatments
- dietitian – recommends the best diet during treatment and recovery
- speech pathologist – rehabilitates patients with communication and swallowing disorders.
- social worker – helps provide emotional support and practical assistance to patients and carers.
Treatment for thyroid cancer usually includes surgery, thyroid hormone replacement therapy and radioactive iodine treatment. Some people also need external radiotherapy or chemotherapy.
Most people receive a combination of treatments. The type of treatments your doctor recommends will depend on the type and stage of thyroid cancer that you have. Discuss any preferences or concerns about treatment with your medical team.
Most patients have surgery to treat thyroid cancer. There are two main types of thyroid surgery:
Partial or hemi-thyroidectomy – only the affected lobe or section of the thyroid is removed. This procedure is often performed if the biopsy is inconclusive and the doctor needs to look at more tissue to determine if you have cancer.
Total thyroidectomy – The whole thyroid gland, including the isthmus, is removed. When the biopsy confirms the cells are cancer, surgeons often suggest patients have a total thyroidectomy to remove undetected cancer cells in other parts of the thyroid gland. A few lymph nodes may also be removed at this time. Afterwards, you may have radioactive iodine treatment (thyroid ablation).
With either type of operation, the surgeon may remove nearby lymph nodes. This is called a neck dissection. It is performed as a preventive measure or if the lymph nodes are enlarged due to the cancer spreading (metastasising).
In very rare cases, the surgeon removes other tissue (for example, the thymus gland and vascular tissues) near the thyroid that has been affected by the cancer.
Thyroid hormone replacement therapy
For many people, the most significant long-term impact of a total thyroidectomy is the fact that it is necessary to take a thyroid hormone replacement for the rest of their life. If your thyroid is removed, you will no longer produce the hormones that maintain your metabolism and keep your body functioning at a normal, healthy rate. Some people who have a partial or hemi-thyroidectomy will also be prescribed T4 to prevent cancer cells from reappearing. You must replace thyroxine (T4) by taking an oral hormone tablet everyday. This hormone tablet:
- prevents the symptoms of hypothyroidism, which can include weight gain, constipation, brittle and dry hair and skin, sluggishness and fatigue
- supplies the body with the missing T4 hormone that your thyroid would normally produce
- suppresses the pituitary gland’s production of thyroid-stimulating hormone (TSH). High levels of TSH may cause cancer cells to grow.
- should not have any side effects, as long as you are on the correct dosage.
Some people receive radioactive iodine treatment about 6 weeks after surgery. During the gap between surgery and further treatment, you may not take hormone replacement medication. Tell your doctor if you are feeling very unwell, as your treatment schedule may be adjusted.
Radioactive iodine treatment
This is a type of internal radiotherapy treatment. You can’t have this treatment if you’re pregnant or breastfeeding.
You will be given a radioactive iodine substance, usually in tablet form. You may also be given a man-made recombinant human thyroid- stimulating hormone (rhTSH) to help your cells take up the radioactive iodine substance. The radioactive substance targets thyroid cancer cells because thyroid cells absorb iodine more than other cells in the body. When it is absorbed, the radiation destroys the cells.
The two types of radioactive iodine treatment are:
Radioactive iodine ablation (thyroid ablation) — radioactive iodine administered after a thyroid operation. The radioactive iodine will destroy any normal or cancerous tissue that remains after surgery.
Radioactive iodine therapy — treatment that is intended to destroy thyroid cancer cells in the body after the first ablation. This therapy is given if tests show that cancer cells are still in your body.
You will need a sufficient amount of TSH in your body for your treatment to be successful. This means that before treatment, you will either have to stop taking any thyroid hormone replacements for two to four weeks or take a man-made recombinant human thyroid-stimulating hormone (rhTSH). You will also have to start eating a low or no iodine diet before treatment. Your health care team will give you advice about which foods to avoid, including seafood, iodised table salt, some dairy products, and foods with certain colourings.
External radiotherapy is the use of high-energy x-rays or electron beams to kill or damage cancer cells. Radiotherapy may be given after surgery, or as an additional treatment to radioactive iodine treatment if the cancer has spread to lymph nodes in the neck. It is commonly used to treat medullary or anaplastic thyroid cancer because radioactive iodine treatment is usually less effective for these types of cancers.
Before your treatments begin, your doctors will schedule a planning (simulation) session and take x-rays to determine the precise area to be treated.
You may have to wear a mask during treatment so the radiation beams always treat the correct areas of your body.
This is usually an outpatient treatment, daily, Monday to Friday for 5-7 weeks. Treatment itself is painless, but you may have some other side effects.
Chemotherapy is the treatment of cancer with anti-cancer (cytotoxic) drugs. The aim of chemotherapy is to kill cancer cells while doing the least possible damage to healthy cells.
Chemotherapy is only very occasionally used in the management of thyroid cancer. It may be given for advanced cancer that has spread (metastasised) to other parts of the body.
Drugs are usually given by injection into a vein (intravenously). You will probably have several sessions of chemotherapy over a few weeks, however your medical team will determine your treatment schedule.
Palliative treatment helps improve people’s quality of life by alleviating symptoms of cancer, without trying to cure the disease. It is particularly important for people with advanced cancer, however, it can be used at any stage of cancer.
Often treatment is concerned with pain relief and stopping the spread of cancer, but it can also involve the management of other physical and emotional symptoms. Treatment may include radiotherapy, chemotherapy or other medication.