There are multiple different options for the treatment of thyroid cancers that can be used alone or in combination:
- Active Surveillance
- TSH suppression therapy
Active Surveillance for Low Risk Thyroid Cancer
Thyroid nodules smaller than 1cm and thyroid cancers that are small (<1 cm in size), show no evidence of lymph node involvement, and are not located on the back surface of the gland (near the recurrent laryngeal nerve) are considered “low risk thyroid cancers” and may be eligible to undergo active surveillance. Active surveillance is when doctors closely monitor a patient’s thyroid condition or cancer over time without giving any treatment. Doctors will intervene with treatment if there is evidence that the cancer has grown, or if the patient’s condition begins to change. Another term for active surveillance is “watchful waiting.” With active surveillance, some patients may be able to avoid surgery, as their cancer may remain small and never grow to a concerning size. Studies have shown that this is a very reasonable option for thyroid nodules smaller than 1cm, and even for those nodules that appear to be cancerous based on ultrasound features or are biopsy-proven papillary thyroid cancer.
For nodules greater than 1cm with worrisome characteristics on ultrasound and biopsy results suggestive of cancer, surgery is the preferred treatment choice. Occasionally, in select cases with large, symptomatic nodules greater than 4 cm, surgery may be chosen without the need for a biopsy to confirm thyroid cancer. The extent of surgery will depend on multiple factors, including the size of the tumour, the histologic type, the location, and the involvement of regional lymph nodes or local structures.
Possible surgeries might include:
Hemithyroidectomy: This is the removal of only one of the thyroid lobes. A Hemithyroidectomy can be considered for some small cancers (< 4 cm) with no evidence of a tumour in the remaining lobe and no evidence of regional lymph node involvement on imaging studies. The remaining lobe should be followed closely with routine ultrasounds after surgery. It is important to note that this procedure is only chosen for low-risk thyroid cancers with no signs of invasion to other tissues. The goals of this procedure are to preserve healthy thyroid tissue and to avoid the need for lifelong thyroid hormone replacement therapy.
Total thyroidectomy: This is the removal of the entire thyroid gland. This is performed in larger tumours (> 4 cm), when there are nodules in both lobes, or if part of the treatment will include giving radioactive iodine (RAI).
Central compartment lymph node neck dissection: This is a type of neck dissection, which involves removing the central compartment lymph nodes, including the lymph nodes next to the trachea and in front of the larynx. This might be recommended if a patient has known cancer in the thyroid gland or enlarged lymph nodes in the area.
Lateral compartment lymph node neck dissection: This is a type of neck dissection, which involves removing lymph nodes from the sides of the neck. This would be done if there is known cancer spread to that area.
Revision thyroid surgery: This is an additional surgery, or re-operation, in the thyroid bed or at the lymph node sites, which could be required if there is evidence that the cancer has recurred, or come back. Recurrence can be picked up on follow-up imaging studies or blood tests.
TSH suppression therapy
Following a total thyroidectomy, patients will need to undergo lifelong thyroid hormone replacement. TSH (Thyroid Stimulating Hormone) is a hormone produced by the brain to stimulate the growth of thyroid tissue and the production of thyroid hormone. When the thyroid gland is removed, the body is unable to produce thyroid hormone naturally. The brain will therefore start producing more TSH to try to increase the production of thyroid hormone. However, elevated TSH can also stimulate the growth of remnant thyroid tissue, which could increase the risk of recurrent thyroid cancer.
After surgery, TSH suppression therapy may be used to decrease a patient’s future risk of disease recurrence. In this type of therapy, patients are given a much larger dose of thyroid hormone (levothyroxine) than is necessary to fulfil their body’s needs. Giving this “larger-than-needed” dose signals the brain to stop producing TSH (as there is already more than enough thyroid hormone in the body), and therefore prevents the growth of additional thyroid tissue. When combined with surgery and RAI (when needed), this treatment has been shown to lower the risk of thyroid cancer recurrence. The side effects of this treatment include a fast and irregular heartbeat and a loss of bone density, which leads to an increased risk of fractures. Doctors will evaluate a patient’s TSH levels, along with other clinical factors, in order to determine the optimal thyroid suppression levels for each individual patient.
Radiation for thyroid cancer comes in two main forms: radioactive iodine (RAI) and external beam radiation therapy.
Radioactive iodine: The main function of iodine in the body is to be used by thyroid cells to make thyroid hormone. Thyroid cells use essentially all of the iodine in the body for hormone production. Well-differentiated thyroid cancer cells also have the ability to take in iodine, just like healthy thyroid cells. Radioactive iodine (I-131) treatment involves administering I-131 (a radioactive isotope of iodine) to a patient either as a drink or in a capsule. The radioactive iodine is then taken up by thyroid cells, both healthy and cancerous. Since it is radioactive iodine, it will damage the thyroid cells and prevent them from growing. This radioactive iodine will affect all thyroid cells, no matter where in the body they are located, but will not damage normal tissue. This treatment is only given to patients who have previously undergone a total thyroidectomy, because these patients should not have any remaining healthy thyroid tissue. This means that that any existing thyroid tissue is likely to be cancerous. In these cases, radioactive iodine is useful because the I-131 will damage the cancerous thyroid cells and prevent them from growing, without affecting any other cells in the body.
External beam radiation therapy: While it remains the standard of care in many cancers of the head and neck, external beam radiation is not often recommended for thyroid cancer. For well-differentiated thyroid cancers, radioactive iodine is preferred because it is a more targeted form of radiation that attacks only thyroid cells and has fewer side effects than external beam radiation.
External beam radiation therapy might be considered in the following circumstances:
- Patients who are over the age of 55 and have T4 disease (gross extra-thyroidal extension).
- Patients who have an aggressive cancer that cannot be completely resected and is not sensitive to radioactive iodine (either in the neck, in the thyroid bed or recurrent disease).
- Patients who have a distant metastasis that is causing significant symptoms and cannot be surgically resected (spine, brain, thorax).
Chemotherapy & Biologic Medications
Currently, very little research has been done on the use of chemotherapy as a treatment for well differentiated thyroid cancer. For patients who have persistent disease despite conventional treatments (surgery, TSH suppressive therapy, and RAI), additional treatment options include watchful observation (discussed above) and systemic chemotherapy. The goal of chemotherapy is to stabilise, or slow, the progression of metastatic disease. In other words, it attempts to prevent the disease from spreading throughout the body. Chemotherapy is considered a disease modifying drug because it is expected to stop disease progression, but it is not expected to improve disease prognosis or provide a cure. Chemotherapeutic drugs can have significant toxic effects that might vary according to the specific chemotherapeutic agent used and the administered dose. Therefore, it is important to limit the use of systemic treatments to only those patients who are at significant risk for morbidity or mortality due to advanced disease.
If recurrent disease is evident after standard treatment, other local treatment therapies can be offered. These other treatments may be able to improve a patient’s quality of life when their disease is symptomatic. If the disease continues to progress despite all previously mentioned therapeutic options, chemotherapeutic drugs may be offered to select patients through clinical trials.
For more information about new therapies for thyroid cancer speak to your medical practitioner.