Thyroid cancer occurs in the cells of the thyroid, which is a butterfly-shaped gland located at the base of the neck. The thyroid produces hormones that regulate the heart rate, body temperature and weight.
There are many types of thyroid cancer. Some grow very slowly and others can be very aggressive. Most thyroid cancer cases can be cured with treatment.
This is the most common kind of thyroid cancer, accounting for about 75% of cases. Papillary thyroid cancers are usually slow growing, but they tend to spread to the lymph nodes in the neck. Most of these cancers can be treated successfully.
There are many subtypes of papillary thyroid cancer. Some less common subtypes of this cancer (follicular variant, tall cell, insular, diffuse sclerosing) tend to be more aggressive and may grow and spread more quickly.
Follicular thyroid cancer is the second most common type of thyroid cancer which accounts for about 15% of cases. This cancer type tends to spread via the bloodstream to other parts of the body such as the lungs and bones.
Medullary thyroid cancer is much less common, accounting for about 5% of thyroid cancers. These cancers arise from the parafollicular C cells in the thyroid. These cells are usually responsible for producing a hormone called calcitonin, which helps to control the level of calcium in the body. Although the outcome of treatment for medullary thyroid cancer is not as good as for papillary and follicular thyroid cancers, many patients can still be treated successfully.
Anaplastic thyroid cancer is the rarest and accounts for about 2% of thyroid cancers. These cancers tend to be very aggressive and grow very quickly and spread rapidly to other parts of the body.
Thyroid cancer is more common in women than men. In Singapore, it is the 8th most common cancer diagnosed in women. Thyroid cancer is commonly diagnosed at a younger age than most other cancers, with most cases occurring in patients below the age of 60 years.
Thyroid cancer typically does not cause any signs or symptoms early in the disease. As thyroid cancer grows, it may cause:
Make an appointment with your doctor if you experience any signs or symptoms that worry you.
There is no known way to prevent thyroid cancer, but the following factors may reduce risk:
It is not clear what causes thyroid cancer, but factors that may increase the risk of thyroid cancers include:
Tests and procedures used to diagnose thyroid cancer include:
Treatment for thyroid cancer depends on several factors, such as staging of the cancer, other existing health conditions the patients may have and their personal preferences.
Thyroid cancer is usually treated with surgical removal of the thyroid. Some patients may require more than one type of treatment, such as surgery in combination with chemotherapy or radiation therapy.
This is the preferred primary treatment option for patients who are fit for surgery.
Radioactive iodine treatment is often used after surgery to eliminate any remaining cancerous thyroid cells and target secondary tumour sites (in the event the cancer has spread to other parts of the body). This treatment may also be used to treat thyroid cancer that recurs after treatment.
Radioactive iodine is usually administered orally, either in a capsule or liquid form. It is primarily taken up by the thyroid cells and cancer cells, reducing the risk of harming healthy cells. The radioactionpatient will pass most of the radioactive iodine out in their urine within a few days, but the treatment will continue to be effective between one to three months.
Radiation therapy uses targeted rays to kill cancer cells. This treatment option is used in cases where surgery cannot be performed or radioactive iodine treatment has been ineffective. It can also be used to slow the growth of cancer that has spread to the bones.
After surgery to remove the thyroid, patients will need to take thyroid hormone medication for life. This is usually an oral medication that is taken once daily. This medication serves a dual purpose – it replaces thyroxine which would have been produced by the thyroid and it helps to significantly reduce the growth of cancer cells by suppressing the hormones that stimulate the thyroid.
Targeted therapy uses drugs that attack specific features of the thyroid cancer, for e.g., certain genetic mutations or the blood vessels that supply the cancer, in order to stop the growth and spread of the cancer cells. These treatments are offered when the thyroid cancer has spread to other parts of the body and are no longer responding to radioactive iodine treatment.
Before surgery, your surgeon will perform comprehensive medical assessments including blood tests and scans to see if you are suitable for surgery and advise on the risks involved. Your treatment recommendation is often based on consensus by a group of medical specialists' opinions (the tumour board), who come together to discuss the benefits and limitations of every treatment strategy.
Before surgery, the anaesthesia team will assess your fitness for surgery and advise you on various aspects of general anaesthesia and pain control after surgery.
Specialist nurses will also provide pre-surgery counselling so that you know what to expect.
After surgery, you will be given regular outpatient appointments to see your team of doctors. During these appointments, you may have blood tests and scans to check if the cancer recurs.
It is important to follow your doctor's advice, keep to your clinic visits and do the recommended scans and tests, so that timely treatment can be administered if the cancer recurs or other problems occur.
Thyroid cancer is diagnosed through physical examinations, blood tests to check thyroid function, fine-needle aspiration cytology (FNAC) to test cells from a thyroid nodule, ultrasound scans to image the thyroid and CT scans to determine if the cancer has spread.
The risk factors for thyroid cancer include being female, a family history of thyroid cancer, exposure to high levels of radiation and inherited genetic conditions like familial medullary thyroid cancer and multiple endocrine neoplasia.
Treatments for thyroid cancer typically involve surgery (either a full thyroidectomy or partial removal), radioactive iodine therapy, radiation therapy and thyroid hormone medication. In advanced cases, targeted therapies may be used.
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