by Eduardo Gonzales, MD
Q.Is thyroid cancer really more common among Filipinos than among other races? A female co-worker was recently diagnosed with papillary cancer of the thyroid. She had her thyroid gland surgically removed and she will undergo radioactive iodine treatment. What are her chances of overcoming this cancer? What does the thyroid gland do? What are the symptoms of thyroid cancer?
A. The thyroid gland is the largest of the endocrine glands. It is located on the neck, just below the larynx (voice box) where the Adam’s apple is. It produces substances called hormones that control many of the body’s metabolic processes including energy use and growth.
Thyroid cancer (i.e., cancer that originates from the thyroid gland) is the most common cancer that affects endocrine glands, yet worldwide, it is rather rare, accounting for less than 1% of all cancers. But among Filipinos—and this should answer your first question—either those living in the Philippines or abroad, thyroid cancer has a relatively high incidence rate. In our country, thyroid cancer is the 7th leading form of cancer, with an estimated 2,500 new cases per year. It is the most common type of cancer among Filipino women between 15 to 24 years old. Thyroid cancer is three times more common in females than in males. It can occur at any age, but its incidence increases with age.
Studies that have been conducted to explain why Filipinos are more prone to cancer than other ethnic groups or nationalities suggest that a combination of genes, and diet and lifestyle factors could be the reason. More Filipinos carry a genetic mutation that makes them more susceptible to the disease. Likewise, among Filipinos there is ahigher prevalence of goiter and thyroid nodules and lower consumption of carotenoids.
The behavior and natural course of thyroid cancer depends on whether it is differentiated or undifferentiated. Undifferentiated thyroid cancers (i.e., where the cells are very immature and primitive looking) are highly invasive while differentiated ones are slow growing.
Fortunately, more than 90% of thyroid cancers are differentiated. Of these, seven out of 10 are either papillary (the type your co-worker has) or mixed papillary-follicular in type. The rest are follicular.
Papillary thyroid cancers are very slow growing so that in many instances, the disease remains undetected during the patient’s lifetime. In fact, papillary cancer of the thyroid gland is an incidental finding in up to 35% of adults at autopsy.
Follicular thyroid cancer is more aggressive than its papillary counterpart. But with proper treatment, the outlook for patients with this type of cancer is still very good.
In over 95% of cases, the principal sign of thyroid cancer is a nodule or lump, usually hard and painless, in the thyroid gland. Not all thyroid nodules, though, are cancerous. In fact, more than 80% of them are benign. The probability of the nodule being cancerous is higher if it is solitary (i.e., there is only one); accompanied by hoarseness; or, occurs in a child or young adult.
Surgery is the treatment of choice for thyroid cancer. In some instances, as in the case of your co-worker, radioactive iodine is given after surgery. Rarely, chemotherapy and/or radiotherapy are also administered.
The outlook for differentiated thyroid cancer is excellent. The 10-year survival rate of those who are treated when the cancer is still confined to the thyroid especially if the tumor is less than or equal to one cm. in size is a high 98%. Even when the cancer has already spread to other organs when initially detected, the five and 10-year survival rates are still 80% and 61%, respectively.
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