Thyroid Cancer Metastatic
Metastatic thyroid cancer occurs when cancer cells spread from the thyroid gland to other parts of the body. While most thyroid cancers have an excellent outlook, understanding what happens when the disease spreads and the available treatment options is essential for patients facing this diagnosis.
Table of contents
- What is metastatic thyroid cancer
- Where thyroid cancer spreads
- Symptoms of metastatic disease
- How metastatic thyroid cancer is diagnosed
- Treatment options
- Outlook and survival
What is metastatic thyroid cancer
Metastatic thyroid cancer is a condition where cancer cells that began in the thyroid gland spread to other parts of the body[1]. The thyroid is a small, butterfly-shaped gland at the base of the neck that produces hormones controlling metabolism, body temperature, heart rate, and blood pressure[2].
About 30% of people with thyroid cancer will have metastatic disease, with most having spread to the lymph nodes in the neck. Only 1-4% of patients have cancer that has spread outside of the neck to other organs such as the lungs and bone at the time of diagnosis[1]. Around 4% of patients with thyroid cancer present with metastatic disease[9].
Metastatic thyroid cancer can be more challenging to treat than cancer limited to the thyroid gland and often requires a combination of therapies[4]. The disease is sometimes called distant metastasis when it spreads to organs far from the thyroid[7].
Where thyroid cancer spreads
When thyroid cancer spreads, it typically follows a pattern, moving first to nearby structures and then to more distant parts of the body. Understanding the most common sites of spread helps doctors plan appropriate treatment and monitoring strategies.
Thyroid cancer can spread to areas close to the thyroid, known as regional metastasis. These locations include muscles, blood vessels, or nerves in the neck, the voice box (larynx), the windpipe (trachea), the esophagus, the bottom part of the throat (hypopharynx), lymph nodes in the neck, and lymph nodes between the lungs[7].
When the cancer spreads to parts of the body farther from the thyroid, this is called distant metastasis. The most common sites include the lungs, bones, the brain, and the liver[7][8]. The lungs, bones, and lymph nodes are the most frequent sites of distant spread[4].
Research has shown that patients who develop spread to multiple organs have a worse outlook than those with cancer in a single organ. In one study, 93 patients had spread to single organs while 32 patients had multi-organ spread[1].
Symptoms of metastatic disease
The symptoms of metastatic thyroid cancer depend on where the cancer has spread in the body. Many patients may not experience any symptoms at all, which makes regular follow-up appointments especially important after thyroid cancer treatment[4].
If thyroid cancer spreads to the lungs, patients may experience shortness of breath, a persistent cough, difficulty breathing, or coughing up blood[4][8].
When cancer spreads to the bones, it can cause bone pain, bone fractures, or bone loss. In some cases, it may lead to compression of the spinal cord[8].
If thyroid cancer spreads to other organs such as the liver, patients may experience abdominal pain, weight loss, or overall discomfort[8]. General symptoms that may occur regardless of where the cancer has spread include tiredness, loss of appetite, nausea and vomiting, and unexpected weight loss[2].
How metastatic thyroid cancer is diagnosed
All patients with thyroid cancer undergo regular monitoring after surgery to detect any signs that the cancer has returned or spread. This surveillance involves several types of tests and imaging studies.
Blood tests are a key part of follow-up care. Doctors measure thyroid stimulating hormone (TSH) levels as well as thyroglobulin levels. Elevated thyroglobulin can indicate that thyroid cancer has returned in the surgical area, that cancer was missed in the lymph nodes during the first operation, or that cancer has spread to other parts of the body[4].
Imaging tests play an important role in finding metastatic disease. A radioactive iodine nuclear uptake scan performed after surgery can show areas where thyroid cancer has spread, as thyroid cancer cells often light up on these scans[4]. Thyroid ultrasound can detect cancer that has spread to lymph nodes in the neck[4].
Cross-sectional imaging such as CT scans or MRI scans can show metastasis in the lungs, while bone scans can reveal cancer that has spread to bones[4]. PET scans, though less commonly used for thyroid cancer compared to other cancer types, can show cancer spread anywhere in the body[4].
When suspicious areas are found, a fine-needle aspiration biopsy may be performed. This involves removing a small sample of tissue from suspicious lymph nodes or other areas to examine for the presence of cancer cells[4].
Treatment options
Treatment for metastatic thyroid cancer depends on several factors, including the type of thyroid cancer (papillary, follicular, medullary, or poorly differentiated/anaplastic), where the disease has spread, previous treatments, and the genetic characteristics of the tumor cells[4].
For cancer that has spread to lymph nodes in the neck, surgical removal is the most effective therapy. Having an experienced thyroid surgeon with expertise in neck dissections is extremely important for the best outcomes[4].
Radioactive iodine treatment is used to treat well-differentiated thyroid cancers that have spread. This includes papillary and follicular thyroid cancers. This treatment works because thyroid cancer cells often take up radioactive iodine, which then destroys the cancer cells[4][9].
When thyroid cancer spreads to the bones, this can cause pain and fractures. In these cases, surgical intervention by an experienced orthopedic surgeon may be needed. External beam radiation therapy can be used in rare situations, including when cancer spreads to the brain[4].
Kinase inhibitors are drugs that block the action of enzymes called kinases. These enzymes add phosphate groups to proteins, which can activate or deactivate various functions in cells. By blocking these enzymes, kinase inhibitors can help treat cancer by preventing uncontrolled cell growth. Some metastatic thyroid cancers contain genetic changes that can be targeted by these medications. For example, vandetanib, a tyrosine kinase inhibitor, targets the RET gene and is used to treat spread in patients with medullary thyroid cancer[4].
In some cases, particularly when cancer has spread to the lungs, doctors may recommend observation without immediate intervention. This approach is used especially if the cancer spots are not growing on repeated imaging studies[4].
The treatment plan for patients with metastatic thyroid cancer should be individualized and developed by a team of specialists working together[3].
Outlook and survival
Most patients with thyroid cancer have an excellent outlook, even if there is spread outside of the neck at the time of diagnosis. However, death from thyroid cancer, while rare, occurs mainly in patients who have spread of the cancer outside of the neck to other organs[1].
When compared with cancer that stays in the thyroid and cancer that spreads to nearby areas, the 5-year survival rates for metastatic thyroid cancer are lower. For localized thyroid cancer the rate is 99.9%, for regional spread it is 97.6%, and for metastatic thyroid cancer it is 54.7%[9].
The outlook varies depending on the type of thyroid cancer. For papillary thyroid cancer that has spread to distant parts of the body, the 5-year survival rate is 76%. For follicular thyroid cancer with distant spread, the rate is 64%[10].
Several factors affect outlook for patients with metastatic thyroid cancer. Patients with cancer spread to multiple organs have a worse outlook than those with spread to a single organ[1]. The average follow-up time in one study was 77 months, with researchers calculating overall survival and recurrence-free survival at 5 years[1].
Despite the challenges of treating metastatic disease, newer targeted therapies have shown promise. Multitargeted kinase inhibitors have demonstrated prolonged overall survival and progression-free survival in patients with metastatic differentiated and medullary thyroid cancers[9].
