Causes
There are several risk factors for developing thyroid cancer. The presence of one or more risk factors does not necessarily mean 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 one or more faulty genes that predispose them to developing thyroid cancer.
- Sex: Women are about three times more likely to develop thyroid cancer than men.
- Age: Commonly diagnosed in people over 40 years old.
- 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.
Symptoms
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 -- may increase in size or press on the trachea or oesophagus, making it difficult to breathe or swallow.
- You may 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) 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.
Diagnosis
Blood test
- Checks the amounts of thyroid hormones in your bloodstream.
- A cancerous thyroid usually continues to function normally, so a blood test may be used to rule out benign thyroid conditions.
- May help diagnose medullary thyroid cancer, which may be indicated by an elevated level of calcitonin.
- Commonly used as a follow-up test, to assess if treatment was effective.
- Sometimes followed by radioisotope scan.
Ultrasound
- A non-invasive, painless scan that uses soundwaves to build up a picture of part of the body.
- Gel is spread over the neck to conduct the soundwaves.
- 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 is a solid tumour or fluid-filled cyst.
- Can also check the lymph nodes in the neck for signs of cancer.
- Painless.
- Outpatient scan.
Biopsy
Tissue is removed for examination under a microscope. Two types:
- Fine needle aspiration -- A needle is inserted into the thyroid (or lump in your neck) and a small tissue sample is removed. An ultrasound machine 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.
Radioisotope scan
- Sometimes 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.
- 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 lie on a table under a machine called a gamma camera.
- The gamma camera will identify how much radioactive liquid is absorbed by cells. 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.
- Sometimes a biopsy is performed.
- Not used to diagnose medullary thyroid cancer.
- Painless.
- No major side effects -- levels of radioactivity after the scan are very low, so it is safe for you to interact with others soon after the scan.
CT (computerised tomography) scan
- A procedure that uses x-ray beams to take pictures of the inside of your body.
- Uses a computer to compile many pictures of areas of your body.
- Sometimes used if the thyroid is enlarged, so your doctor can make sure your trachea (windpipe) is not too compressed.
- Unlikely to be used to diagnose papillary or follicular thyroid cancer -- usually used as a follow-up test, or after surgery.
- A special dye is injected into your veins before the scan -- this makes scan pictures clearer.
- It may make you feel flushed or hot for a few minutes. Rarely, more serious reactions occur, such as breathing difficulties or low blood pressure.
- You will lie still on a table while the CT scanner, which is large and round like a doughnut, slowly moves around you.
- Painless.
- Takes 10-30 minutes.
- Outpatient scan.
MRI (magnetic resonance imaging) scan
- A scan that uses a combination of magnetism and radio waves to build up detailed cross-section pictures of the body.
- You will lie on a table in 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.
- Talk to your doctor if you have a pacemaker or other metallic object in your body, or if you're claustrophobic.
- Commonly used as a follow-up test.
- Painless.
- Usually takes an hour.
- Outpatient scan.
PET (positron emission tomography) scan
- Specialised imaging test - only available at some hospitals.
- Used to determine if cancer has spread, and commonly used as a follow-up test.
- Talk to your doctor if you are diabetic.
- You will be given a radioactive glucose solution. Active cancer cells will have an increased uptake of this solution.
- Your body is scanned.
- Painless.
- Usually takes several hours.
- Outpatient 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
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. Your outcome depends on:
- the type of thyroid cancer
- test results
- the rate and depth of tumour growth
- how well you respond to treatment
- other factors such as age, fitness and your medical history.
Treatment
The type of treatment you have depends on:
- the type of cancer you have
- the stage of the cancer
- recommendations of your medical team
- what you want.
Surgery
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.
- Often performed as a diagnostic measure (biopsy).
Total thyroidectomy
- The whole thyroid gland, including the isthmus, is removed.
- Surgeons often advise patients to have a total thyroidectomy because undetected cancer cells may exist in other parts of the thyroid gland, and this operation reduces the likelihood that further surgery will be required.
- Afterwards, you may have radioactive iodine treatment (thyroid ablation).
With either type of operation, it may be necessary for the surgeon to remove tissues from the area around your thyroid gland:
- If lymph nodes are removed, this procedure is called a neck dissection.
- Neck dissections are performed as a preventative measure, or if the lymph nodes are enlarged due to the cancer spreading (metastasising).
- In rare cases, the surgeon must remove other tissue near the thyroid.
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
The use of high-energy x-rays or electron beams to kill or damage cancer cells.
- Most commonly used to treat medullary or anaplastic thyroid cancer.
- May be given after surgery, instead of surgery, or as a treatment for advanced cancer.
- 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 the radiation beams always treat the correct areas of your body.
- Usually outpatient treatment, daily, Monday to Friday for 5-7 weeks.
- Treatment itself is painless, but you may have some other side effects.
Chemotherapy
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
Palliative treatment helps improve people’s quality of life by alleviating symptoms of cancer, without trying to cure the disease.
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.
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:
- cancer nurse coordinator - supports you throughout treatment and answers your questions
- dietitian - recommends the best diet during treatment and recovery
- 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
- 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
- radiation oncologist - plans and administers radiotherapy
- social worker - helps provide emotional support and practical assistance to patients and carers
- speech pathologist - rehabilitates patients with communication and swallowing disorders.