Introduction
Thyroid cancer is the 18th most common cancer in women but is much less common in men. Each year in Europe approximately 25,000 people will be diagnosed as having thyroid cancer. The number of new cases has increased over the past 25 years and varies considerably from country to country. For instance, Germany has three times more new cases of thyroid cancer each year than the UK whilst France has twice as many cases as the UK, but it is Iceland that has the highest incidence of any nation in Europe.
Back to top
The Thyroid Gland
The thyroid gland sits at the front of the throat wrapped around the trachea (windpipe) and just above the level of the shoulders. It is an ‘H’ or a butterfly-shaped gland. Normally, you cannot see or feel it but the thyroid can be generally enlarged (which is called a goitre) or develop nodules which can be felt or may be visible.
The thyroid gland is an endocrine gland secreting hormones into the bloodstream. The hormones are: thyroxine (T4), triiodothyronine (T3) and calcitonin.
T3 and T4 control the speed of the body’s metabolism. More T3 and T4 speeds up the body’s processes while less slows the metabolism down. People with too much T3 and T4 appear overactive, jumpy and usually lose weight despite a healthy appetite. Not enough T3 and T4 have the opposite effect so people become slow and put on weight.
In addition the thyroid gland produces calcitonin which has some role in controlling the body’s calcium levels, but patients whose thyroid gland has been removed do not suffer any ill effects due to a lack of calcitonin. With medullary cancer, too much calcitonin is produced.
Very close to the thyroid gland are the four parathyroid glands. They are very small and are not part of the thyroid. Their function is to control the calcium level in the blood. More parathyroid hormone raises the blood calcium leading to thirst and other symptoms. If the blood calcium falls below normal, it can cause a pins and needles sensation in the face, hands and feet, muscle spasms in the hands and sometimes fits.
Underproduction of parathyroid hormone (hypoparathyroidism), can occur after surgery to remove the thyroid gland - it is sometimes impossible not to remove or damage the blood supply to the parathyroids.
Patients with hypoparathyroidism receive treatment with calcium, vitamin D (calciferol) or alfacalcidol which is converted in the body to vitamin D.
Back to top
Thyroid Cancers
There are four different types of thyroid cancer. Two of these are differentiated (DTC) cancers which means that the cancer cells have a close resemblance in structure and function to normal thyroid cells. The differentiated thyroid cancers are:
- Papillary carcinoma - the most common, accounting for about 75-85% of all cases, occurring mainly in younger women.
- Follicular cancer - affects slightly older people but is less common than papillary carcinoma and accounts for about 10-15% of all cases; Hürthle cell cancer (less than 5% of all cases) is a particular form of follicular cancer that tends to grow more rapidly than other cancers of this type.
The two remaining types of thyroid cancer are:
- Medullary carcinoma - this is rare (less than 5% of all thyroid cancers) and sometimes hereditary.
- Anaplastic carcinoma - also uncommon, accounting for less than 5% of all cases across Europe, but there are big differences from country to country.
Most thyroid cancers can be treated effectively, especially the DTCs, although they can recur. As with all forms of cancer, early diagnosis usually means simpler treatment and better results.
Back to top
Thyroid Cancer Risk Factors
For reasons nobody understands, thyroid cancer is three times more common in women. Most tumours occur in people aged between 20 and 60. Asian people are also more prone to developing thyroid cancer.
Follicular cancers are more common where diets are low in iodine, which is an essential ingredient of T4 and T3.
Exposure to radiation is a further risk factor – patients who have been treated with radiotherapy for other conditions have an increased risk of thyroid cancer, as do people affected by nuclear fallout. Almost 2,000 cases of thyroid cancer resulted from the nuclear power station explosion at Chernobyl over 20 years ago. It released large quantities of radioactive iodine into the atmosphere which resulted in increased numbers of thyroid cancers for approximately 10 years afterwards, but is no longer a problem.
Medullary cancer, the least common of the thyroid cancers, is inherited in approximately 20% of cases. Some papillary and follicular thyroid cancers also seem to run in families, but the genetic basis for this remains unknown.
Back to top
Preventing Thyroid Cancer
Apart from a family history of thyroid cancer, most people who develop the disease have no known risk factors so prevention is not possible in most cases.
Patients with a family history of any form of thyroid cancer should always be alert to the possibility that they too might be affected and seek advice at the earliest sign of any suspicious symptoms.
Back to top
Symptoms of Thyroid Cancer
- a painless lump in the front of the neck which gradually increases in size
- a painless lymph node in the side of the neck
- difficulty in swallowing
- difficulty in breathing - both due to pressure effects of an enlarged thyroid gland on the oesophagus (gullet) and trachea (windpipe)
- hoarseness of the voice
Symptoms of an overactive or underactive thyroid gland are not usually present in thyroid cancer. An overactive thyroid causes people to be very active, lose weight despite a good appetite, and feel hot when other people are feeling cold.
An underactive thyroid gland causes people to be sluggish, sleepy all the time, have no energy, put on weight, and to develop a thicker coarser skin, gaining hair in some areas, but losing it in others.
Back to top
Diagnosing Thyroid Cancer
Any of these symptoms will require further tests to determine the cause and this can usually be done as an outpatient. Many of these symptoms may be due to other illnesses and may also be caused by other thyroid gland problems that are nothing to do with thyroid cancer.
Lumps in the thyroid gland can be tested by taking a sample through a needle (a fine needle aspirate). This produces a small amount of fluid (aspirate), which can then be examined under the microscope for cancer cells.
An ultrasound scan can distinguish between solid lumps and fluid-filled cysts, but not between benign and cancerous solid lumps.
Radioactive isotope scans are also sometimes used. Cancer cells absorb less radioactive iodine than normal thyroid cells so cancers often show up as “cold spots”, but so do cysts and benign nodules so this is not the best test to make a diagnosis.
For many patients a final diagnosis of thyroid cancer will only be obtained at surgery to remove a lump in the thyroid gland.
There is no valid screening method for thyroid cancer using blood tests.
Back to top
Treating Thyroid Cancer
Thyroid cancers must be treated using surgery, usually removing the thyroid gland altogether, and so removing the cancer.
Radiotherapy is used following surgery. In follicular and papillary cancers radioactive iodine and external beam radiation can be used. In medullary and anaplastic cancers external beam radiotherapy is used.
Chemotherapy, drug treatment, is not normally used in thyroid cancer, except for some anaplastic tumours.
Differentiated Thyroid Cancers: Papillary and Follicular Thyroid Cancer
Treatment for the two types of differentiated thyroid cancers – papillary and follicular thyroid cancers are very similar.
Both carcinomas are usually treated using surgery, removing the thyroid gland completely.
Papillary and follicular thyroid cancer cells absorb iodine and so can also be treated after surgery using a radioactive isotope of iodine, I-131. This kills any cancer cells that have spread away from the thyroid gland. It is usually given 4-6 weeks after surgery and can be repeated if necessary. It is important to stress that radioactive iodine is not an alternative to surgery, but a very useful additional treatment.
Medullary Thyroid Cancer
Patients with medullary thyroid cancer are treated surgically with complete removal of the thyroid gland (total thyroidectomy), with removal of all the lymph nodes and fatty tissues in the central part of the neck, and on the tumour side of the neck. External beam radiotherapy is also used to treat any remaining or relapsing areas of cancer.
Anaplastic Thyroid Cancer
For patients diagnosed at an earlier stage, a total thyroidectomy is the best treatment. For all others, external beam radiation provides the most benefit, in some instances combined with chemotherapy treatments.
Back to top
Surgery
Removal of the thyroid gland is called ‘total thyroidectomy', in which the whole gland is removed. Thyroid surgery is safe but after the whole gland is removed, replacement hormone tablets are needed to prevent the symptoms of an underactive thyroid. The exact amount will be determined following monitoring blood tests. There is the possibility that a nerve which goes to the larynx (voicebox) can be affected by surgery, resulting in a hoarse or weak voice, although this is rarely permanent. In 1-4% of cases hypoparathyroidism may occur as a consequence of total thyroidectomy.
Radioactive Iodine Therapy
Radioactive iodine is used in addition to surgery in treating the papillary and follicular forms of thyroid cancer. A radioactive isotope of iodine known as Iodine131 or I-131 is given as a capsule or as a liquid. The thyroid gland is the only organ in the body that absorbs iodine, and so radioactive iodine can be used to destroy (or ablate) thyroid tissue including thyroid cancer cells in papillary and follicular thyroid cancers. Radioiodine must be given 4-6 weeks after surgery to hypothyroid patients not taking any substitution therapy with T4. The recent introduction of recombinant TSH makes it possible to treat some patients, depending on their risk factors, without making them hypothyroid for weeks.
Several treatments with iodine may be needed. The first one will get rid of any normal thyroid tissue which takes up iodine even more readily than do cancer cells. Subsequent doses will then be taken up by thyroid cancer cells wherever they are and therefore spread to other places (metastases) can also be treated in this way. Medullary and anaplastic thyroid cancers do not take up iodine and this treatment is not suitable for these tumours.
For some days after treatment with radioactive iodine, patients are temporarily radioactive, so precautions need to be taken to avoid exposing other people, particularly children and pregnant women, to radiation. There are regulations in all countries which specify what precautions should be taken to ensure that the exposure of others is as low as is reasonably achievable.
There are other short term side effects of radioactive iodine treatment which include some tenderness of the neck, sometimes nausea, a dry mouth, changes in taste and swelling of the salivary glands. Normally the latter can be overcome by drinking plenty of fluids and sucking sweets or chewing gum.
Low-dose treatments are all that are usually required. This will have no effect on either female or male fertility, but all patients are advised to avoid conception for 6 months.
Men who receive large doses of radioactive iodine, usually for the treatment of cancer that has spread to other body areas, may have a low sperm count and can sometimes become infertile as a result. Large doses of radioactive iodine also affect women’s ovaries causing irregular periods for some months after treatment.
Radioactive iodine treatment is safe and has been successfully used to treat thyroid cancer for over 50 years.
External Beam Radiation
External beam radiation uses high-energy rays generated from machines outside the body to destroy cancer cells and is used to treat medullary and anaplastic cancers. External beam radiation is not normally used to treat follicular or papillary carcinomas of the thyroid except in specific circumstances. External beam radiotherapy and surgery are used in combination for some patients.
External beam radiation usually involves treatments given in small doses several days a week for a few weeks. The treatment itself is entirely painless but there is usually some reaction in surrounding tissues, including the skin, which results in changes to the skin and sometimes difficulty in swallowing, hoarseness of the voice and fatigue. Providing the treatment in small doses allows non-cancer cells time to recover in between treatments.
Back to top
Looking after Yourself
Radioactive iodine, given as a capsule or as a liquid, is used in addition to surgery in treating the papillary and follicular forms of thyroid cancer.
For some days after treatment with radioactive iodine patients are temporarily radioactive, so precautions need to be taken to avoid exposing other people, particularly children and pregnant women, to radiation.
There are regulations in all countries, which specify what precautions should be taken to ensure that the exposure of others is as low as is reasonably achievable.
Other short term side effects of radioactive iodine treatment include some tenderness of the neck, which can be treated with painkillers if need be, sometimes feeling sick which rarely requires medication, a dry mouth, changes in taste and swelling of the salivary glands.
Normally the dry mouth and changes in taste can be overcome by drinking plenty of fluids and sucking sweets or chewing gum.
Whatever the problem, do not assume that nothing can be done about it – ask your doctor or nurse: do not just grin and bear it.
Back to top
Questions for your Doctor
Most patients with thyroid cancer are treated by endocrinologists or specialist thyroid surgeons, who will refer patients to radiotherapy or nuclear medicine specialists when necessary.
Before making up your mind about the best treatment option for you, you will need information about your cancer, the treatments available in your area and what this will entail, what to expect from the treatment, what side effects you might experience and how these may change over time as well as what your doctors believe would be most effective in combating your cancer.
For different patients the answers will be different, so it is important to discuss all these issues with your doctor so that you make the right choice for you.
You will have your own questions but some issues you might want to raise are:
- What does the treatment involve?
- What are the benefits I might get?
- How good are my chances of getting those benefits?
- Could having treatment make me feel worse? If so in what way?
- Are there alternative treatments?
- What are the risks of the treatment?
- Are the risks minor or serious? How likely are they to happen?
- What care will I need after treatment?
- What happens if something goes wrong?
- What may happen if I don’t have the treatment?
Back to top
Conclusion
There is no one solution to the management of thyroid cancer, but for clinical and personal reasons particular treatments will suit some patients better than others so patients need comprehensive information so that they can make the right decision for them.
Back to top