The thyroid gland is a butterfly-shaped gland located in front of the neck. Thyroid gland produces thyroid hormones. It is secreted into the blood and then reaches all the cells in the body. Thyroid hormone helps the brain, heart, muscles, and other organs in the body to function as they should.
What is thyroid cancer?
Thyroid cancer is the cancer arising in thyroid gland. Thyroid cancer is a very common disease. We all know at least someone with thyroid cancer.
Thyroid cancer can occur at any age, although it is most common after the age of 30, and its severity increases significantly in patients over the age of 55. Women are three times more likely to develop thyroid cancer than men. Therefore, the majority of thyroid cancer patients are women above the age of 30.
According to a 2020 ICMR study, the incidence of thyroid cancer among women in Kerala is on the rise, and thyroid cancer is most common in Kerala’s Thiruvananthapuram and Kollam districts.
What are the symptoms?
In most patients, cancer first appears as a nodule (lump) in the thyroid, which usually does not cause any other symptoms.
Often, thyroid nodules are discovered incidentally during a neck scan for other medical reasons (e.g., sore throat). Some people may notice a lump in the neck when looking in the mirror, buttoning a collar, being noticed by friends, tightening a necklace, etc.
Rarely, thyroid cancers and nodules can cause symptoms. If a nodule is large enough to compress your windpipe or esophagus, it can cause difficulty breathing and swallowing. In some cases, thyroid cancer affects the nerves that control the vocal cords, and in such patients, thyroid cancer can manifest as voice changes and shortness of breath. Rarely, thyroid cancer symptoms may include neck pain, ear pain, jaw-bone pain, and back pain.
What causes thyroid cancer?
Thyroid cancer is more common in people with a positive family history, in women, and in people over the age of 40.
Those exposed to high doses of radiation and those who received high-dose radiation exposure during childhood are at increased risk of developing cancer. Exposure to radioactivity during nuclear disasters (Chernobyl accident or Fukushima disaster in 2011) has been associated with an increased risk of developing cancer, especially in children.
However, for most people, it is not clear why this cancer develops.
How is thyroid cancer diagnosed?
Thyroid nodules are very common, and less than 10 percent of nodules have a cancer risk. Cancers in thyroid nodules usually do not cause symptoms. Blood tests usually do not help detect thyroid cancer. Thyroid blood tests, such as TSH, are usually normal even when you have cancer.
The best way to find a thyroid nodule is to make sure your doctor examines your neck as part of a routine health checkup.
Your doctor can confirm or suspect that you have cancer based on your medical history, symptoms, and your physical examination. If so, the doctor will prescribe an ultrasound scan of the neck and a Guided FNAC or needle test from the thyroid. CT scan and MRI scan may also be suggested in some cases. In most cases, the results of the scan and needle test will help your doctor confirm whether cancer is present. But in some cases, there is a possibility of receiving ambiguous reports.
Cancer can be diagnosed only after surgical removal of the nodule.
What are the different types of thyroid cancer?
Papillary thyroid cancer: Papillary cancer is the most common type of thyroid cancer. 70% to 80% of thyroid cancers are papillary cancers. Papillary cancer can occur at any age. It grows slowly and often spreads to the lymph nodes in the neck. Papillary cancer generally has a good prognosis even if it has spread to the lymph nodes.
Follicular thyroid cancer: Follicular variant of thyroid cancers accounts for 10% to 15% of cancers. Follicular cancer can spread through the blood to other organs, especially the lungs and bones. Follicular cancer cannot be detected by needle aspiration. If in doubt, the thyroid gland should be removed and examined.
Medullary thyroid cancer: Medullary cancer (MTC) accounts for about 2% of thyroid cancers. About 25% of MTCs occur in family members. In family members of an affected individual, testing for a genetic mutation in the RET proto-oncogene may lead to early diagnosis of medullary thyroid cancer and, consequently, curative surgery.
Anaplastic thyroid cancer: This variant of cancer is one of the deadliest cancers known to mankind. Anaplastic cancer is very rare, occurring in 2% of patients with thyroid cancer. Anaplastic cancer is the most severe and aggressive form of thyroid cancer. This variant is less likely to respond to treatment.
What are the treatment options?
Surgery: Surgery is the main treatment for thyroid cancers. These cancers are often cured with surgery alone, especially if the cancer is small.
Surgery can be done by removing only the cancerous part known as lobectomy / hemithyroidectomy or total thyroidectomy or complete removal of the thyroid gland.
The extent of surgery depends on factors such as the size of the tumor and whether or not the tumor has spread outside the thyroid gland. If the cancer has spread to the lymph nodes in the neck, these lymph nodes must also be removed. This surgery is called neck dissection.
Recent studies suggest that if you have a small tumor less than 1 cm in diameter, called a papillary thyroid microcarcinoma, you can be treated without surgery.
Radioactive iodine therapy (I-131 therapy): The procedure to remove remnants of the thyroid gland after surgery is called radioactive iodine ablation.
Radioactive iodine therapy is usually done after the gland is removed if the cancer is advanced stage, has spread to the lymph nodes, or if the doctor thinks the cancer is likely to come back.
The radioactive iodine used in the ablation procedure has little effect on tissues outside the thyroid. However, in some patients who receive large doses of radioactive iodine, the radioactive iodine can affect the salivary glands and cause dry mouth. If high doses of radioactive iodine are needed, there may also be a small risk of developing other cancers later in life. Although this risk is small, the risk increases with increasing doses of radioactive iodine. The risks of treatment can be minimized by using the smallest possible dose. If iodine therapy is required, your doctor will explain the necessary preparations for it.
Chemotherapy: Cancer that has spread outside the neck (metastatic) is rare, and cancers that do, or when radioactive iodine therapy is not effective, require other types of treatment. Chemotherapy drugs such as sorafenib, dabrafenib, and trametinib are used to treat these cancers. Although these drugs cannot cure cancer completely, they can slow or partially reverse the growth of cancer.
Radiation: When other treatment methods fail, external beam radiotherapy is often prescribed to improve the patient’s quality of life. It can kill or slow the growth of cancer.
What are the side effects of thyroidectomy?
- Neck wound and scar mark
- Numbness in the neck
- You will need to take thyroid hormone for the rest of your life
- Parathyroid gland damage occurs in 4% of patients and requires calcium supplements if this occurs.
- Temporary/permanent voice change (in 2% of patients)
- Transient/permanent shortness of breath (in 2% of patients)
- All surgeries can have complications – infection, bleeding, etc.
- Adverse effects of anesthesia – These will be explained to you by the anesthetist before the operation.
How are the follow-up tests?
All patients with cancer need follow-up examinations after initial treatment, as there is a risk of recurrence of cancer.
Apart from the neck examination, the doctor also prescribes ultrasound scan, blood test, iodine scan and PET scan if required.
If the thyroid is removed, you will need to take thyroid hormone (levothyroxine) for the rest of your life. The pill dosage for patients with cancer is different from that taken after normal thyroid surgery. TSH levels in the blood need to be suppressed to prevent cancer from returning. It requires higher doses of levothyroxine. The TSH level is a good indicator of whether the levothyroxine dose is correct. This requires the services of an experienced oncology doctor.
Another important blood test is measuring the level of thyroglobulin (Tg) in the blood. Rising thyroglobulin levels are a sign of cancer return. In addition to routine blood tests, the doctor may order an iodine scan to determine if cancer cells remain. These scans are more likely to be needed in high-risk patients.
How’s the treatment results or prognosis?
Treatment outcomes for papillary and follicular cancers are excellent, especially in following type of patients,
- those below 55 years of age
- early stages of cancer
- if papillary cancer has not spread outside the thyroid gland
- if the tumor does not have aggressive histology
Treatment outcomes are still better even if the patient is older than 55 years or has a large tumor or is having aggressive histology. But the possibility of recurrence of the disease is high.
Cancer that cannot be completely removed by surgery or destroyed by radioactive iodine treatment may not have the best results. However, despite the fact of living with cancer, these patients can still live a long and quality life.
The expected outcome of cancer treatment varies from person to person. It is important to talk to your doctor about it. Lifelong follow-up is necessary even after successful treatment.