Thyroid cancer is a disease in which malignant (cancer) cells form in the tissues of the thyroid gland. The thyroid is a gland located at the base of the neck, and it produces hormones that help regulate heart rate, blood pressure, body temperature, and weight. There are four main types of thyroid cancer: papillary, follicular, medullary, and anaplastic.
What Causes Thyroid Cancer?
The exact cause of thyroid cancer is not known, but certain factors can increase the risk of developing the disease:
- Gender – women are 2-3 times more likely to develop thyroid cancer than men
- Age – thyroid cancer is more common in older adults, with most cases occurring in people over the age of 40
- Radiation exposure – especially in childhood, such as radiation treatment to the head and neck
- Family history – having a first-degree relative with thyroid cancer increases risk
- Diet low in iodine
- Certain genetic conditions, like multiple endocrine neoplasia
In most cases, it is not clear what causes any single person’s thyroid cancer. Doctors cannot explain why one person develops the disease and another does not.
What are the Stages of Thyroid Cancer?
The stage of thyroid cancer describes how far the cancer has spread at the time of diagnosis. Staging is based on the size of the tumor, whether it has spread to nearby lymph nodes, and whether it has metastasized to distant organs. Thyroid cancer stages include:
- Stage I: The tumor is less than 2 cm and limited to the thyroid.
- Stage II: The tumor is greater than 2 cm but less than 4 cm and limited to the thyroid.
- Stage III: The tumor is larger than 4 cm and limited to the thyroid OR any size tumor that has spread to nearby lymph nodes.
- Stage IVA: The tumor has spread beyond the thyroid to nearby tissues of the neck, such as the larynx, trachea, esophagus, or recurrent laryngeal nerve.
- Stage IVB: The tumor has spread well beyond the thyroid to distant lymph nodes, organs, bones, or other distant sites.
Stage IV thyroid cancer is divided into stages IVA and IVB to designate whether the spread is localized to nearby neck structures (IVA) or has spread to distant sites (IVB).
What is Last Stage or Stage IV Thyroid Cancer?
Last stage or stage IV thyroid cancer refers to cancer that has advanced and spread beyond the thyroid gland. This includes:
- Stage IVA: Cancer has spread locally to invade nearby structures in the neck, such as the larynx, trachea, esophagus, recurrent laryngeal nerve, or major blood vessels.
- Stage IVB: Cancer has metastasized, or spread to distant lymph nodes, organs, bones, or other faraway sites in the body beyond the neck area.
Stage IV thyroid cancer has a worse prognosis than earlier stage cancers that are confined to the thyroid gland. However, treatment can still be effective for some patients to control or slow the progression of advanced disease.
Common Sites of Spread in Stage IV Thyroid Cancer
The most common sites thyroid cancer spreads to in stage IV include:
- Lungs – The lungs are the most common site of distant spread. Thyroid cancer often metastasizes to the lungs before other distant organs.
- Bones – The bone is the second most common metastasis site, especially the pelvis and spine.
- Liver – The liver is a relatively frequent site of spread.
- Brain – Brain metastases occur in about 5-13% of patients with metastatic thyroid cancer.
- Other – Thyroid cancer may also spread to distant lymph nodes, the kidneys, breast, colon, and other organs more rarely.
Symptoms of Stage IV Thyroid Cancer
Symptoms of stage IV thyroid cancer depend on where the cancer has spread. Some common symptoms may include:
- Difficulty swallowing – if the cancer invades the esophagus or compresses the throat.
- Hoarse voice – if the recurrent laryngeal nerve is impacted.
- Cough – if the tumor compresses or invades the trachea.
- Shortness of breath – from lung metastases or fluid around the lungs (pleural effusion).
- Bone pain – from bone metastases.
- Abdominal pain – from liver or other organ involvement.
- Neurologic symptoms – such as headaches, seizures, or mental changes from brain metastases.
Symptoms will depend on the location and extent of spread. Some patients may not have any noticeable symptoms in the early stages of metastatic disease.
Diagnosis of Stage IV Thyroid Cancer
Tests to diagnose stage IV thyroid cancer may include:
- Imaging studies – CT, MRI, PET scans to detect spread to lymph nodes, lungs, liver, bones, brain, and other organs.
- Biopsy – Fine needle aspiration or surgical biopsy of suspicious areas to confirm cancer spread.
- Blood tests – Levels of thyroglobulin and thyroid stimulating hormone (TSH) are markers used to monitor for recurrence.
- Scans – Radioiodine scans if cancer cells take up iodine, bone scans for suspected bone metastases.
The patient’s symptoms and exam findings will help guide which tests are needed to assess the extent of cancer spread.
Treatment of Stage IV Thyroid Cancer
Treatment options for stage IV thyroid cancer include:
- Surgery – To remove as much of the thyroid tumor and metastasized cancer as possible. This may help reduce symptoms and tumor burden.
- Radioactive iodine (RAI) – Patients whose tumors take up iodine can receive targeted RAI therapy to destroy cancer cells.
- External beam radiation – For localized control of tumor growth causing symptoms.
- Chemotherapy – Drugs like doxorubicin, targeted therapy drugs, or immunotherapies may be used.
- Supportive care – To control pain and other symptoms and maintain quality of life.
Treatment focuses on controlling the cancer, managing symptoms, and supporting quality of life. With advanced thyroid cancer, cure may not be possible, so goals are tailored to the individual patient.
Prognosis of Stage IV Thyroid Cancer
The prognosis depends on many factors:
- Type of thyroid cancer – Some types have better outcomes than others
- Patient’s age and overall health
- Extent of spread – Widespread vs isolated metastases
- Response to treatment – How well it can be controlled
On average, about 50% of patients with stage IV papillary or follicular thyroid cancer live 5 years after diagnosis. However, prognosis is highly variable depending on the individual circumstances.
5-Year Survival Rates By Type
| Thyroid Cancer Type | 5-Year Relative Survival Rate |
|---|---|
| Papillary (Most common) | 55% |
| Follicular | 50% |
| Medullary | 50% |
| Anaplastic (Least common) | 7% |
Patients should discuss their individual prognosis with their cancer doctor, who can consider specific details about the case.
Conclusion
In summary, last stage or stage IV thyroid cancer has advanced and spread beyond the thyroid gland to other areas of the body. Common sites of spread include the lungs, bones, liver, and brain. Treatment focuses on controlling cancer growth and managing symptoms. Prognosis at this stage depends on many factors, including the type of thyroid cancer and extent of spread. With advanced disease, treatment goals emphasize quality of life. Patients should work closely with their cancer care team to understand their prognosis and treatment options.
