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What is Medullary Thyroid Cancer?
Medullary thyroid cancer (MTC), also known as medullary thyroid carcinoma, is a relatively rare but distinct type of thyroid cancer that arises from the parafollicular cells (C cells) of the thyroid gland. These cells are responsible for producing the hormone calcitonin, which helps regulate calcium levels in the blood. Unlike other thyroid cancers, MTC is often associated with genetic mutations and can be part of inherited syndromes.
Types of Medullary Thyroid Cancer
Accounting for approximately 2-4% of all thyroid cancers, MTC can be sporadic or hereditary, with distinct clinical and genetic features.
Sporadic MTC
This type occurs randomly and accounts for about 75-80% of all MTC cases. It typically affects older adults without a family history of the disease and usually presents as a single tumor in one lobe of the thyroid. Mutations in the RET proto-oncogene, specifically in the somatic cells, are a common feature in sporadic cases.
Hereditary MTC
Hereditary forms account for the remaining 20-25% and are caused by a genetic mutation that is passed down from a parent to a child. There are two main types of hereditary MTC:
- Multiple endocrine neoplasia type 2 (MEN2) : This is a group of disorders that affect several endocrine glands, including the thyroid, adrenal glands, and parathyroid glands. There are two types of MEN2:
- MEN2A: This is the most common type of MEN 2. In addition to MTC, people with MEN 2A may also develop pheochromocytomas (tumors of the adrenal glands) and parathyroid hyperplasia (overgrowth of the parathyroid glands).
- MEN2B: This is a less common type of MEN 2. In addition to MTC, people with MEN 2B may also develop pheochromocytomas, marfanoid habitus (a tall, thin body type with long limbs), and mucosal neuromas (small tumors of the nerves in the lips, tongue, and eyelids).
- Familial medullary thyroid carcinoma (FMTC): This is a condition in which people have a genetic mutation that increases their risk of developing MTC, but they do not develop any other features of MEN 2.
Symptoms of Medullary Thyroid Cancer
Early-stage MTC is often asymptomatic. As the disease progresses, symptoms may include:
- Neck mass or lump: The most common initial symptom is a palpable lump in the neck, which may grow over time.
- Hoarseness or voice changes: As the tumor grows, it can affect the nearby nerves, leading to voice changes or hoarseness.
- Difficulty swallowing or breathing: A large tumor may compress the esophagus or trachea, causing difficulty in swallowing or breathing.
- Diarrhea and flushing: Elevated calcitonin levels can cause symptoms like diarrhea and facial flushing.
Diagnosis of Medullary Thyroid Cancer
Accurate diagnosis of MTC involves a combination of clinical evaluation, imaging, and laboratory tests. The following are the major diagnostic procedures for MTC:
- Physical examination: Initial assessment typically involves a thorough neck examination to detect any palpable lumps or abnormalities.
- Blood tests: Elevated levels of calcitonin and carcinoembryonic antigen (CEA) in the blood can be indicative of MTC.
- Ultrasound: Neck ultrasound is often the first imaging test used to evaluate the thyroid gland and surrounding lymph nodes.
- Fine Needle Aspiration (FNA) Biopsy: If a nodule is detected, an FNA biopsy is performed to obtain tissue samples for microscopic analysis of the cells.
- Genetic testing: Since MTC can be sporadic or hereditary, genetic testing for mutations in the RET proto-oncogene is crucial. The outcome of a thorough medical history (that is, if you have a family history of MTC or MEN2A syndromes) usually necessitates genetic testing.
- Additional imaging: CT scans, MRIs, and PET scans may be used to assess the extent of the disease and detect metastases.
Stages of Medullary Thyroid Cancer
Doctors use the American Joint Committee on Cancer (AJCC) TNM staging system to classify medullary thyroid cancer (MTC). This system helps doctors determine the extent of the cancer and plan the best course of treatment. This system considers three key factors:
- Tumor size (T): This describes the size and extent of the primary tumor in the thyroid gland.
- Lymph node involvement (N): This indicates whether the cancer has spread to nearby lymph nodes.
- Distant metastasis (M): This determines if the cancer has spread to distant organs beyond the thyroid gland and lymph nodes.
Each factor is assigned a number (0-4) based on the severity. The combination of these TNM categories is then used to assign an overall stage (I-IV) to the cancer. A lower stage indicates a less advanced cancer with a better prognosis, while a higher stage indicates a more advanced cancer.
Treatment Options for Medullary Thyroid Cancer
The management of MTC requires a multimodal approach, tailored to the patient’s specific condition. Treatment options typically include:
Surgical Treatment
The primary treatment for MTC is surgical removal of the thyroid gland (total thyroidectomy) along with affected lymph nodes (lymph node dissection). This is often followed by careful monitoring of calcitonin levels to detect any residual disease.
Although surgical treatment of MTC can effectively remove cancer, it also carries a relatively minor level of risks such as potential damage to surrounding structures and complications from anesthesia.
Post-surgical care typically includes thyroid hormone replacement therapy and regular follow-up to monitor for recurrence.
Radiation Therapy
In cases where surgery is not completely effective or feasible, external beam radiation therapy may be considered to target remaining cancer cells. This is done by delivering high-energy rays to the thyroid area. Radiation therapy can be effective in controlling localized MTC and preventing recurrence. However, this procedure may result in some side effects such as skin changes, fatigue, and effects on surrounding tissues.
Chemotherapy
Chemotherapy works by targeting rapidly dividing cells, including both cancerous and healthy cells. Traditional chemotherapy is less effective in MTC compared to other cancers but may be used in specific scenarios, such as advanced MTC that does not respond to other treatments.
Commonly used drugs include doxorubicin and cisplatin.
Chemotherapy is typically administered in cycles, with specific regimens tailored to the patient’s needs. Due to its impact on healthy cells, chemotherapy can cause a wider range of side effects. Some of these include nausea, fatigue, and increased risk of infection.
Targeted Therapy
For advanced or metastatic MTC, targeted therapies such as tyrosine kinase inhibitors (e.g., vandetanib, cabozantinib) have shown promise in controlling disease progression. These drugs specifically target genetic mutations and molecular pathways involved in cancer growth.
Prognosis of Medullary Thyroid Cancer
The prognosis of MTC varies based on several factors, including the stage at diagnosis, age, genetic profile, and response to treatment. Early-stage disease confined to the thyroid gland has a favorable outcome, with a 10-year survival rate exceeding 80-90%. Advanced disease with distant metastases has a poorer prognosis, with a 10-year survival rate around 20-40%.
Living with Medullary Thyroid Cancer
Impact of Medullary Thyroid Cancer on Quality of Life
Treatment options like surgery, radiation, and chemotherapy can take a toll on a patient’s physical health, causing fatigue, changes in appearance, and other side effects that need management.
MTC does not only affect the patient’s physical health but their mental health as well. The diagnosis and treatment of MTC can also be emotionally challenging. For some, this may lead to anxiety, depression, and stress. Mental health support is therefore vital following a diagnosis of MTC. The disease and its treatment can also affect social life and relationships. Open communication with family and friends, and participating in support groups, can help navigate these challenges.
Support Groups and Resources for Patients
It’s important for patients to have access to psychological support, whether through counseling, support groups, or mental health professionals. Support groups in particular can be especially helpful as they can either be in-person or online and provide emotional support and practical advice from others who have also had an experience with the disease.
Organizations like the American Cancer Society and the Thyroid Cancer Survivors’ Association (ThyCa) provide valuable resources and support networks for patients and their families.
ThyForLife Health also offers an anonymous global community supporting all thyroid conditions, including all types of thyroid cancer. Currently, the community is available only in the English language. To join this community, download the ThyForLife app on the Apple App Store or Google PlayStore.
Key takeaways
- Unlike the more common forms of thyroid cancer (papillary and follicular), medullary thyroid cancer accounts for approximately 2-4% of all thyroid cancers.
- Awareness and early detection, particularly in families with hereditary risk, are crucial for effective management and improved prognosis.
- Advances in genetic testing and targeted therapies are promising, improving outcomes for patients with this challenging disease.
- Many patients live long, fulfilling lives with proper treatment and management of MTC.
