Thyroid cancer is a rare cancer. There are 4000 new cases per year in France (for 40 000 breast cancers). It concerns women at 75%. Its incidence is increasing in all countries.
In Canada, in 2010, thyroid cancer was diagnosed in approximately 1,000 men and 4,100 women. This cancer is the 5 the largest cancer female (4.9% of cases), but only 0.3% of cancer deaths in women. The diagnosis usually occurs in people aged 25 to 65 years.
This cancer is often detected at an early stage. The treatment is then very effective with a cure in 90% of the cases. Improved screening techniques could also explain why the diagnosis is more frequent. Indeed, one can now detect small tumors formerly invisible.
Risk factors for thyroid cancer
Thyroid cancer is favored by exposure of the thyroid to radiation, either because of radiotherapy treatments in the head, neck or upper chest, especially during childhood, either in because of radioactive fallout in areas where nuclear tests have been carried out after a nuclear accident such as Chernobyl. The cancer may appear several years after the exposure.
The increase of thyroid cancers.
Sometimes there is a family history of thyroid cancer or a genetic syndrome (such as adenomatous familial polyposis). A gene mutation promoting medullary thyroid cancer has been identified.
Thyroid cancer can develop on a goiter or thyroid nodule (about 5% of nodules are cancerous).
Several types of cancer
The thyroid gland has three types of cells: follicular (which secretes thyroid hormones), parafollicular cells around them and secretes calcitonin (involved in calcium metabolism), as well as non-specialized cells (supporting tissues or blood vessels). .
Cancers develop from follicular cells in more than 90% of cases; according to the appearance of cancer cells, we speak of either papillary cancers (in 8 out of 10 cases) or vesicular cancers. These cancers evolve slowly and are sensitive to radioiodine treatments.
More rarely (10% of cases), medullary cancer – develops from parafollicular cells or from non-mature cells, these tumors being called undifferentiated or anaplastic. Spinal and anaplastic cancers evolve more rapidly and are more difficult to treat.
When to consult?
At the beginning of the disease, thyroid cancer usually does not cause any signs or symptoms. It can be discovered then “by chance” during the palpation of the neck or cervical ultrasound performed for another cause.
It can also be discovered when monitoring a goiter or a benign nodule.
As it develops, any of the following symptoms may occur, but in the vast majority of cases they are related to benign thyroid abnormalities (95% of the thyroid masses are benign nodules) or to other more commonplace pathologies:
- More or less painful discomfort in the neck or throat;
- Palpable mass or visible at the front of the neck or on the sides and corresponding then to lymphadenopathy (hypertrophy of the lymph nodes;
- Change of voice, which becomes more hoarse;
- Difficulty swallowing or breathing
- More or less painful discomfort in the neck or throat;
- Modification of a nodule or a goiter known.
How to diagnose thyroid cancer?
In most cases, the situation is that of the discovery of a thyroid nodule which must be known whether or not causes thyroid dysfunction and its benign or malignant nature.
The ultrasound confirms whether a nodule is present, the number, the size and the location. She checks for the presence or absence of lymphadenopathy
Cytopuncture (non-painful needle aspiration) removes cells for examination and may provide arguments for or against a malignant tumor
These examinations can be supplemented by a thyroid scan, a CT scan or an MRI.
When a thyroid cancer is suspected, it is often the surgical procedure with histological examination of the tumor that allows or not to confirm it.
Can we prevent thyroid cancer?
There is no real prevention, but people who have been treated by irradiation at the head and neck or those living in areas where nuclear tests have been conducted should be given regular, simple monitoring. (palpation of the thyroid region).
The few who are at very high risk for thyroid cancer because of a genetic mutation can discuss with their doctor the interest of a possible preventive thyroidectomy, in order to remove the thyroid gland. We must then weigh the advantages and disadvantages of this option.
For people living near a nuclear power plant, emergency measures to protect the thyroid gland are provided for in the event of an accident that would be accompanied by releases of nuclear waste. Potassium iodide, also known as stable iodine, is a drug that blocks the effects of radioactive iodine on the thyroid. The thyroid gland fixes iodine, whether radioactive or not. By saturating the gland with non-radioactive iodine, the risk of damage can be reduced.
The methods of distribution of this drug vary from one municipality to another and from one country to another. People who live near a plant can get information from their municipality.
Thyroid cancer treatments
The treatment depends on the type of cancer , its degree of evolution, but also the age of the person and his state of health.
It often combines several therapeutic approaches, surgery, radioactive iodine and thyroid hormones but other treatments such as external radiotherapy or medical treatment are possible.
The choice of treatment is discussed during a multidisciplinary consultation – surgeon, endocrinologist, anesthetist, radiotherapist, and oncologist – and the decision taken after information and discussion with the patient.
Any treatment is accompanied before and after “supportive care”, pain management, psychological support, sometimes voice rehabilitation, help with administrative procedures, social support … etc.
Radioactive iodine treatment
This treatment uses high doses of a radioactive form of iodine. It is often used after surgery, to destroy leftover thyroid gland as well as possible metastases to reduce the risk of recurrence. Radioactive iodine is administered as a capsule or liquid to swallow. This treatment may cause nausea, dryness of the mouth and eyes, and an altered sense of taste and smell. Radioactive iodine is eliminated through the urine within a few days.
Radioactive iodine emits radiation that can be detected by the next day’s scintigraphy and can detect the persistence of cancer cells throughout the body. For a few days, he imposes precautions against the entourage by avoiding contact with pregnant women or young people less than fifteen years.
Radiation therapy is used either for tumors that cannot be surgically removed, or after surgery if it has not been able to remove the entire tumor, or in case of recurrence. . Radiation therapy may cause moderate fatigue, temporary irritation of the skin of the neck or mucous membranes of the mouth and pharynx.
Chemotherapy or targeted therapies are rarely used. They are proposed in case of metastases or when the tumor has not or not fully responded to treatment.
This treatment also affects healthy cells and often causes side effects, such as nausea.
Rare forms of thyroid cancer
Medullary cancers are usually treated with surgery, possibly combined with external radiotherapy and / or chemotherapy. They are not sensitive to radioactive iodine.
Anaplastic cancer, very rare, occurs most often in the elderly. Nor is it sensitive to radioactive iodine.
The rare forms or refractory forms of thyroid cancer are sent to expert centers such as the TUTHYREF network (THYroid Tumors REFRactaires) or the RENATEN network.
Regardless of the treatment, the person will be monitored for blood levels of thyroid hormones, the side effects of radiotherapy or chemotherapy and the identification of possible recurrences or appearances of metastases.