Thyroid cancer

Introduction and incidence

The thyroid gland is a gland located in the lower front of the neck, and consists of 2 lobes connected by a thin layer of tissue (isthmus). The thyroid gland uses iodine to produce hormones, which affect the body's metabolic rate and the level of calcium in the blood. There are several types of this cancer, and the main 4 are papillary, follicular (these 2 have the best prognosis and are also called differentiated thyroid cancer), medullary and anaplastic. Anaplastic carcinoma is aggressive and has a poor prognosis, but fortunately it is very rare. Thyroid cancer is generally much more common in women than in men, and according to data from the Croatian Cancer Registry from 2017, it accounted for 5% of all new cancer cases in women.

​Risk factors

Some of the risk factors for thyroid cancer are age (most often between the ages of 25 and 65), female gender, exposure to radiation to the neck at a young age, a family history of thyroid cancer, and certain genetic syndromes (multiple endocrine dysplasia types 2A and 2B, familial medullary thyroid carcinoma). If a patient is diagnosed with an inherited genetic syndrome, family members at risk will also be referred for testing. You can read more about risk factors for cancer in a separate article.

​Signs and symptoms

Early thyroid cancer usually does not cause symptoms and is often discovered by chance, for example during a routine examination. As the tumor grows, a lump in the neck, difficulty breathing, difficulty or pain in swallowing, and hoarseness may occur.

Figure 1. Thyroid scintigraphy with radioactive iodine I-131 (so-called body scan). The purpose of the scan is to confirm that the tumor tissue is accumulating iodine (black accumulations in the image), so that the full therapeutic dose of radioactive iodine can then be administered. (Source: Wikipedia)

Diagnosis

The basis is a detailed examination of the patient (especially palpation of the neck) and taking a thorough medical history. It should be noted that thyroid nodules are common, and the vast majority of them are not malignant. A basic examination of the thyroid gland is performed with an ultrasound of the neck, and if any of the nodules look suspicious, the doctor will perform a puncture of the nodule, after which a diagnosis of thyroid cancer is established or ruled out by analysis under a microscope. Thyroid hormones, antibodies to thyroid tissue, and tumor markers - thyroglobulin (Tg) for papillary and follicular carcinoma and calcitonin for medullary carcinoma - can be analyzed from the blood. You can read more about cancer diagnostics in a separate article.

Treatment

Thyroid cancer is treated depending on the type of tumor and the stage of the disease. Surgical treatment plays a major role and is often the first method of treatment. It may involve the removal of only one lobe affected by the tumor (lobectomy) or the removal of the entire thyroid gland (total thyroidectomy). After surgery, especially of the entire thyroid gland, patients usually have to take thyroid hormones in pill form for life. Hormone regulation is very important because if there is too much stimulation of the thyroid gland to produce hormones, this can also stimulate tumor cells to grow. Radiotherapy is used in 2 main ways. The first is standard external beam radiotherapy, which is used in some patients after surgery if a high risk of disease recurrence is determined or the tumor has not been completely removed, or instead of surgery when surgery is not possible for any reason. The second option is the administration of radioactive iodine I-131, which is used in many patients with papillary and follicular thyroid cancer after surgery, and can also be used in patients with metastatic thyroid cancer. This is a precise type of therapy that uses the thyroid gland's ability to accumulate iodine, so other healthy tissues are spared from radiation. Radioactive iodine scintigraphy (test application of I-131) is performed before (and after) the mentioned therapy, in order to confirm that the tumor tissue accumulates iodine (Figure 1). Chemotherapy is sometimes used, mainly for advanced medullary and anaplastic carcinomas that cannot be treated with radioactive iodine. More recently, targeted therapy has appeared, including sorafenib and lenvatinib (papillary and follicular cancer), vandetanib and cabozantinib (medullary cancer), and dabrafenib and trametinib (anaplastic cancer with BRAF mutation present). The application of immunotherapy is also being researched.

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