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The cancer increasing most rapidly among women worldwide, is that of the thyroid1. In Singapore, thyroid cancer has also been on the rise, and is the eighth most common cancer among women here.
We speak to Medical Oncologist Dr. Toh Chee Keong to understand why thyroid cancer occurs, how it’s detected and treated, and how patients can prevent a relapse.
The thyroid, a small but crucial gland just above your collarbone, produces hormones that regulate your body’s metabolic rate.
As a result, many parts of your body, including your heart, muscles, digestive system, brain and bones, depend on the thyroid functioning well. For example, the thyroid controls the pace at which your heart beats and you burn calories.
A study on thyroid cancer cases in Singapore over 1974 to 20132 revealed that thyroid cancer affected more women than men, at a ratio of three to one. Most of these cases were diagnosed when the patients were in their 50s. The study also found that there were more cases of thyroid cancer among Malays and Chinese as compared to Indians.
Though it remains unclear as to what causes thyroid cancer, factors associated with an increased risk include exposure to radiation (especially in childhood), higher Body Mass Index (BMI), and aspects of the female reproductive system.
Similarly, the reasons for the rise of the cancer are inconclusive, but possibly could include the increased rate of screening, and the greater detection of smaller cancers due to improved technology.
Thyroid cancer often occurs without symptoms, and could be picked up when a doctor notices a small swelling, also known as a nodule, around your thyroid during a check-up.
When there are symptoms, these commonly take the form of a lump or swelling in your neck from larger nodules. These could lead to other signs, such as changes to your voice or hoarseness, difficulties swallowing, breathlessness or a cough.
Your doctor would confirm the cancer by conducting a biopsy of tissue extracted from the nodule either by a fine-needle or through surgery if needed.
There are four main types of thyroid cancer: papillary, follicular, medullary and anaplastic. The same study reported that papillary thyroid cancer, a slow-growing form which can sometimes spread to the lymph nodes, was the type most commonly diagnosed, at around 38% of all cases.
The good news is that, once detected, thyroid cancer is highly treatable. Though its incidence has increased, the mortality rate has remained constant, at around 2%. The most common recourse is surgery to remove part or all of the thyroid.
If necessary, this is followed by radiation therapy or radioactive iodine therapy.
“For thyroid cancer, chemotherapy is not really effective as it’s applied to the whole body and the cancer tends to be localised. In addition, the more common thyroid cancer cells are not sensitive to chemotherapy. Radiation is to focus [on the thyroid area],” explained Dr. Toh.
However, treatment may include chemotherapy or immunotherapy if the thyroid cancer is anaplastic – the least common and most serious type.
Though surgery is usually effective, this may have to be complemented by several courses of action to ensure that the cancer does not return.
Medication
Following treatment, most patients take medication indefinitely, which will help to replace the hormone thyroxine that their thyroid can no longer produce, or which it produces less of.
The higher the chance of relapse, the greater the dosage of medication that patients need to take. This is because thyroxine stimulating hormones (TSH), which direct your thyroid to produce thyroxine, stimulate the growth of thyroid cancer cells.
Hence, increasing the level of thyroxine via more medication, helps to suppress the cancer-prompting TSH. Doctors check that the prescribed dosage of medication is sufficient through blood tests that monitor TSH levels.
Radioactive Iodine Therapy
Radioactive Iodine Therapy may be recommended for patients with a higher risk of relapse. As the thyroid cells are the only cells in your body which can absorb iodine, the therapy, which involves taking a pill, destroys any remaining thyroid cells using radioactive iodine and helps prevent a relapse.
Healthy lifestyle
Given that a high BMI is one of the associated risk factors for thyroid cancer, adopting a healthy lifestyle can also guard against a relapse.
“Exercise regularly, eat a balanced diet, and try to reduce stress,” advised Dr. Toh.
As thyroid cancer is becoming more and more frequently discovered, especially among women, it’s advisable to monitor the health of your thyroid. Should you discover any growth or swelling around your neck, have your doctor examine it to determine if there’s any cause for concern.
[2] JH Shulin, J Aizhen, SM Kuo, WB Tan, KY Ngiam, R Parameswaran. 2018. Rising incidence of thyroid cancer in Singapore not solely due to micropapillary subtype. Ann Royal Coll of Surg Engl;100(4): 295—300.
