Thyroid Cancer is an uncommon cancer but is increasing in incidence.
In the last 30 years the incidence has increased from 2.2 to 10.6 per 100.000 population. It can occur at any age and may present in children and young adults. It is more common in women.
The Thyroid is a gland consisting of two lobes and is wrapped around the trachea in the lower neck. It is an endocrine gland and produces thyroid hormone which controls all aspects of metabolism.
Development of a cancer in the thyroid does not usually affect the metabolism of the patient.
What Are the Causes of Thyroid Cancer?
The only known cause is ionising radiation such as X rays. This is responsible for only a tiny fraction of thyroid cancers and may occur in patients who have received radiation treatment for another cancer early in childhood.
These cancers are treated in the same way and respond as well as spontaneously occurring cancers.
For most thyroid cancers there is no obvious cause.
What Are the Symptoms of Thyroid Cancer?Most thyroid cancers present with a painless swelling in the front of the lower neck.As they tend to grow very slowly they do not usually cause any problems with breathing or swallowing until they are quite large. Sometimes the first sign is a lump in the side of the neck.This is due to the spread of the cancer from the thyroid gland to a lymph gland in the neck.
What Are the Treatments for Thyroid Cancer?
Many people have small lumps or nodules in their thyroid and the majority are benign and it is important not to over diagnose or over treat these. An ultra-sound of the neck is the most used imaging study and this examines the thyroid gland and the neck nodes. If the ultra-sound is suspicious for malignancy then a Fine Needle Aspiration is done to examine the cells.
If cancer is confirmed or seems very likely, and treatment with surgery is planned then a CT scan may help guide the surgery.
The most common type of cancer is called Papillary and the next is Follicular.
The mainstay of treatment is surgical. If the cancer is small with no adverse features then removal of one lobe is sufficient.
If the tumour is larger or if there are lymph nodes and additional treatment is required, then the whole thyroid is removed. The additional treatment is Radioactive Iodine [I 131]
This is given to ablate residual normal thyroid tissue and to eradicate any residual thyroid cancer tissue. This could be around the thyroid, in small lymph nodes in the neck or rarely in the lungs or bones. The radioactive iodine is given as a capsule and is called an “unsealed isotope”. It targets the thyroid cancer cells very specifically and apart from a little uptake in the salivary glands it is not absorbed by any other cells in the body.
It can give a very high dose of radiation directly into the cancer cells without injuring other cells. In particular this treatment does not affect fertility which is important as many thyroid cancer patients are young women of child-bearing age. It has therefore been possible to cure patients, even if the papillary cancer has spread to their lungs.
Patients are admitted to hospital for 2-3 days for this treatment. In some patients, mostly older patients the tumour does not take up enough radioactive iodine to be effective and then the tumour can be treated with External Beam Radiation like other cancers in the Head and Neck area.
Patients who have had a total thyroidectomy will need to be on replacement thyroid hormone. This is taken as a once a day tablet and is exactly the same as the thyroid hormone produced by the thyroid gland. Conventional cytotoxic chemotherapy has not been helpful in thyroid cancer but newer drugs such as Tyrosine Kinase inhibitors are beginning to find a place.
Overall the cure rate is high in the region of 85-90%. This is reassuring in a tumour which affects young people. Although young people tend to have more lymph node involvement they do better. Nodal disease does not carry the same prognostic effect as it does with other tumours. Thyroid cancer is not generally linked with other types of cancer.
What Are the Side Effects?
The surgical scar usually heals very rapidly and tends to fade as time passes.Sometime the parathyroid glands are affected and patients may need to take calcium for a while.
Radioactive iodine can potentially cause a dry mouth, but this is usually after repeated doses for widespread disease.
The best person to discuss radiation therapy is a Radiation Oncologist. You can ask your Surgeon or General Practitioner for a referral to a Radiation Oncologist for a discussion about whether radiation therapy is a suitable treatment for you.
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