Understanding thyroid cancer: risk factors, symptoms, treatment and outcomes

Thyroid cancer accounts for around 1% of all cancer cases in the UK, with approximately 3,900 people diagnosed each year. It refers to cancer that starts in the thyroid gland, a butterfly-shaped organ that sits below your voice box (larynx), with one lobe on either side of your windpipe (trachea). It produces hormones that help regulate your metabolism and how much calcium is available in your blood. 

Here we’ll look at the different types of thyroid cancer, symptoms, treatment and outcomes. 

Types of thyroid cancer

Your thyroid gland contains two types of cells: follicular and parafollicular. Your follicular cells make thyroid hormone, which regulates your metabolism, and your parafollicular cells make another hormone called calcitonin, which helps control calcium levels in your blood. Thyroid cancer can start in either of these two types of cells. 

Most types of thyroid cancer start in the follicular cells; this includes papillary thyroid cancer, follicular thyroid cancer and oncocytic (hurthle cell) thyroid cancer. Less commonly, thyroid cancer starts in the parafollicular cells — this is called medullary thyroid cancer.

Thyroid cancer can also be categorised according to its differentiation state — this refers to how closely the cancer cells resemble typical thyroid cells. Anaplastic thyroid cancer, the fifth type of thyroid cancer, is undifferentiated, meaning its cells do not resemble typical thyroid cells. It is rare but aggressive.

Differentiated thyroid cancer refers to cancer cells that closely resemble typical thyroid cells. Around 90% of thyroid cancer cases are differentiated. In a minority of cases, thyroid cancer is poorly differentiated, where the cancer cells look less like typical thyroid cells.

Stages of thyroid cancer

Thyroid cancer can be categorised according to how far it has progressed, ranging from stage 1 to 4.

At stage 1, the cancer is limited to within the thyroid gland. At stage 2, the cancer has begun to grow beyond the thyroid gland into the surrounding muscle. At stage 3, the cancer has spread from the thyroid gland into your lymph nodes (small glands containing white blood cells that help fight infection). 

At stage 4, the cancer has spread well beyond your thyroid gland into other organs, such as your lungs and/or brain. 

Who is at risk of thyroid cancer?

Age and genetics

Thyroid cancer is two to three times more common in women and usually occurs in people in their late thirties or aged over 70. Your genetics can also play a role, particularly in medullary thyroid cancer. 

If you have the gene fault (mutation) for medullary thyroid cancer, it is recommended that you undergo a thyroidectomy before cancer develops. In children screened, this surgery may occur as early as before their first birthday. 

There is also a presumed genetic link with papillary thyroid cancer where it has been shown that you are six times more likely to develop it if you have a first-degree relative (ie parent, sibling or child) who has been diagnosed with papillary thyroid cancer. 

Weight

Being overweight increases your risk of developing thyroid cancer by 23% for every five-unit increase in your body mass index (BMI). The speed at which you gain weight also affects your risk, with rapid weight gain increasing your risk more than gradual weight gain. Conversely, losing excess weight has a protective effect. 

Type 2 diabetes or insulin resistance also increases your risk of thyroid cancer.

Radiation

Exposure to radiation can increase your risk of thyroid cancer, particularly papillary thyroid cancer.

In the UK, exposure to CT scans (which use ionising radiation) in early childhood, or radiotherapy during treatment for childhood cancer increases your risk of thyroid cancer, usually with a 10-year lag between radiation exposure and the onset of thyroid cancer. 

Environment 

Over the last 30 years, rates of thyroid cancer have doubled in men and tripled in women, with rates continuing to rise. Although this is in part due to higher rates of diagnosis due to more and better quality scanning for other conditions, it is also thought to be due to exposure to higher levels of carcinogens (cancer-causing agents) in the environment. 

Symptoms of thyroid cancer

The most common symptom first noticed is a lump that you can see or feel in your neck. You may also notice changes in your voice, feel a lump in your throat when swallowing and/or become breathless more easily. 

In most cases of thyroid cancer, thyroid hormone levels are within the normal range. 

When to see a doctor

As with most cancers, the sooner it is detected, the greater the chances of successful treatment. Consequently, if you notice a lump in your neck or a change in your voice or swallowing that doesn’t start to improve after around two weeks, see your GP.

Often, a lump in the thyroid is a non-cancerous nodule; however, around one in 20 thyroid nodules are cancerous. 

Diagnosing thyroid cancer

Your doctor will recommend an ultrasound scan of your neck to detect a lump or if a lump is obvious, to more closely examine its nature and size. 

Your lump will be graded from one to five, with five denoting the highest likelihood of cancer. 

If your lump is graded three or higher, a tissue sample (biopsy) will need to be collected by inserting a fine needle into your lump (fine needle aspiration). You will receive a local anaesthetic first to numb the area of your neck from which the biopsy is collected. 

Treating thyroid cancer

Surgery

The most common treatment for thyroid cancer is surgery to remove part or all of your thyroid gland. A balance must be struck between ensuring all of the cancer is removed and minimising damage to the tissue and surrounding structures. 

Surgery is performed under a general anaesthetic. If you have half of your thyroid removed, you will likely be able to go home the following morning. If your entire thyroid is removed (total thyroidectomy), you will usually need to stay in hospital for two nights, while your blood calcium levels are monitored.  

During your surgery, the nerves responsible for your voice will be continually monitored. This is because they travel along the undersurface of your thyroid gland on either side and thyroid tissue needs to be carefully separated away from them. Nerve monitoring ensures the function of these nerves is tracked throughout your surgery. 

In around one in every 100 thyroid removal surgeries, these nerves are damaged, causing a weak voice and weak cough after surgery. In very rare cases, one in 10,000, nerve damage causes difficulty breathing after surgery.

If your lymph nodes are removed as part of your operation, a drain will be inserted, that is, a tube through your skin to collect any tissue fluid produced by your neck. This is usually removed after two nights. 

Your surgeon will take steps to minimise scarring and before you leave hospital, will advise you on scar management for the next few months to prevent unnecessary scarring. 

Post-surgery treatment

You may need further treatment after surgery. For example, if you have papillary or follicular thyroid cancer and the cancer has spread or looks as if it might be aggressive, your specialist may recommend radioactive iodine treatment. This treatment is given orally as a capsule under supervision with a period of isolation during treatment. 

Your thyroid cells use iodine to produce thyroid hormone. Radioactive iodine will, therefore, be taken up by any thyroid cells left in your body after surgery and will help prevent any spread of cancer by killing the remaining cancer cells that weren’t previously detected.

Non-surgical treatments

If your cancer can’t be removed surgically, your doctor may recommend radiotherapy, which applies high-energy waves to the area where your cancer is located to kill the cells. 

If your thyroid cancer has not responded to other treatments and is, therefore, deemed incurable, you may receive an immunotherapy called tyrosine kinase inhibitor (TKI) treatment. This can shrink or slow the growth of your cancer to help relieve some of your symptoms. 

Your treatment options

All patients with thyroid cancer are cared for by a thyroid cancer multidisciplinary team at their local cancer hospital. This ensures a consensus can be achieved on the most suitable treatments for you and options can be presented to you before any treatment is started. 

Every decision about treatment is guided by you, with your specialist ensuring that you understand the risks and benefits of each option. 

Thyroid cancer and pregnancy

As the most at-risk age group in women for thyroid cancer is the late thirties, some women may develop thyroid cancer while pregnant. 

It is important to note that the thyroid gland can naturally become larger during pregnancy and, therefore, this symptom does not necessarily mean cancer is present. Nonetheless, any noticeable change in your thyroid gland should always be investigated. 

As in other adults, surgery is still the most common treatment in pregnant women who have thyroid cancer. This is considered safe during the first and second trimesters. Surgery in the third trimester has a risk of pre-term labour and so, if required, this decision would be made in close liaison with your obstetrician. 

If you need radioactive iodine treatment after surgery, this shouldn’t be given within six weeks of breastfeeding as lactating breast tissue also absorbs iodine — there is, therefore, a theoretical risk of increasing your risk of breast cancer.

Preparing for treatment

It is important to be in the best possible health before your treatment, particularly if you’re having surgery. You should, therefore, quit smoking, follow a healthy diet and exercise regularly.

Getting a diagnosis of thyroid cancer can be overwhelming, which is why it’s also important to write down any questions you have before you meet your specialist to discuss your treatment plan. Bringing a friend or family member with you to your appointment can help so that they can take in the information provided too.

Treatment outcomes

Cancer outcomes are measured using a five-year survival rate, that is, recording the number of people who survive for at least five years after their cancer diagnosis or starting treatment. 

This is because the most intensive period of monitoring and follow-up is during this time as your risk of cancer returning is low after five years. You should, however, remain vigilant and see your GP if you notice a new lump or symptom. 

Most types of thyroid cancer have a high five-year survival rate. The five-year survival rate for papillary thyroid cancer in women is 95% and in men is 85%; for follicular thyroid cancer, it is 90% in women and 85% in men; and for medullary thyroid cancer, it is 75% in women and 70% in men. However, for anaplastic thyroid cancer, the five-year survival rate is less than 5% for men and women. 

These survival rates are averages for each type of cancer; however, in the early stages, survival rates tend to be higher. 

Life after treatment

After treatment for thyroid cancer, it is important to follow as healthy a lifestyle as possible to reduce your risk of the cancer returning. This involves not smoking, losing excess weight, controlling health conditions such as diabetes, exercising regularly and following a healthy, balanced diet. 

You will also have regular blood tests to check for tumour markers, your thyroid hormone levels and, in some cases, your calcium levels. You may be given a medication that suppresses thyroid stimulating hormone (TSH) to further reduce the risk of your thyroid cancer returning. 

If you have had your entire thyroid gland removed, you will need to take thyroid hormone replacement tablets once a day for the rest of your life. Your thyroid hormones will also be monitored for the rest of your life to ensure your dosage is correct.