What is thyroid cancer?

Coming up next week is National Thyroid Cancer Awareness Week, mandated by Republic Act 10786 which sets the fourth week of September as the time dedicated to inform the public of this condition. Thyroid cancer is the most prevalent endocrine-related cancer in the Philippines.

The thyroid is a small butterfly-shaped gland just above your collarbone in the front of the neck. It makes thyroid hormone, a substance that controls your metabolism.

Any enlargement of the thyroid is called a goiter. The whole thyroid can be enlarged, or just a small part which can be a cyst that is filled with fluid, or a nodule if it is a solid mass. Thyroid nodules are common and can go undetected until they grow large enough to be visible or felt in the neck, or they may be found incidentally when another test is done like a CT scan or X-ray of the head and neck or the chest, done for other reasons.

Most thyroid cancers don't cause any signs or symptoms early in the disease. Concerning signs and symptoms include rapid growth of thyroid nodules; changes to your voice, including increasing hoarseness; difficulty swallowing; and swollen lymph nodes on the side of the neck.

Risk factors for thyroid cancer include:

•Exposure of the head and neck to radiation in childhood

•Genetic mutations, such as medullary thyroid carcinoma, which can run in families

•Iodine deficiency may make patients with goiter be more susceptible to some types of thyroid cancer

•Significantly more females than males are diagnosed with thyroid cancer

Most thyroid nodules are usually benign masses and not cancer. But once a thyroid nodule is discovered it should be evaluated to check that it is not cancer. A neck ultrasound is the best test to evaluate a thyroid nodule. The size and appearance of these nodules are described and a scoring system is used to assess the possibility of the presence of cancer.

If the nodule is highly suspicious for cancer, a biopsy, called a fine-needle aspiration biopsy (FNAB), should be done. This is performed with the guidance of ultrasound, using a needle and syringe similar to that used when blood is drawn from your arm for laboratory tests. It is an out-patient procedure that takes about 30 to 60 minutes and patients can go home right after with a small bandage on the neck. Biopsy results are typically available in a few days.

If thyroid cancer is found, complete removal of the thyroid or a total thyroidectomy is recommended for high-risk patients, and this includes Filipinos, due to the high risk of spread and recurrence. This cancer can metastasize to the brain, bones, lymph nodes and lungs. Fortunately, most thyroid cancers (papillary and follicular thyroid cancer) are slow to grow and slow to spread, but there is a type that can be highly aggressive, called anaplastic thyroid cancer.

Unlike some cancers that require several courses of chemotherapy, most types of thyroid cancer are treated with radioactive iodine (RAI) which is given as a single dose in a capsule, and this may be all that is needed to destroy any remaining thyroid tissue.

Patients who have their whole thyroid removed are considered hypothyroid and have to take thyroid hormone (levothyroxine) replacement for life. In thyroid cancer the dose is higher than those being treated for other causes of hypothyroidism. This is to help prevent the recurrence and spread of thyroid cancer. Regular blood tests are done every three to six months for dose adjustment and to detect recurrence.

Thyroid hormone should be taken regularly, first thing in the morning on an empty stomach. One way to remember is to place the medication next to your bed and to take it upon waking. Take it only with water and wait at least 30 minutes before taking any other food or medication.

If you think you have a goiter, consult your doctor to get the correct diagnosis. With early detection and timely treatment, most thyroid cancers are highly curable, with five-year survival rates at 98.3 to 99.9 percent in those without distant spread.