This is a rare tumor that arises from cells called the parafollicular c cells. These cells are present within the thyroid gland and secrete a number of proteins. This cancer is attributed to inherited genetic mutations in up to 25% of patients. Medullary thyroid cancer is usually diagnosed when a patient presents with a lump in the thyroid or enlarged lymph nodes in the neck. This tumor spreads to the local lymph nodes earlier than the papillary and follicular types of cancer.
Evaluation and management of this rare type of cancer requires an experienced team of doctors, especially as this cancer may be associated with involvement of other organs of the body. These patients need evaluation and treatment for associated conditions such as pheochromocytoma (a tumour of the adrenal glands) and hyperparathyroidism (tumours in parathyroid glands).
My FNAC is reported as medullary carcinoma of thyroid can I go ahead with surgery or do I need any other test.
Apart from the routine investigations the following tests must be done
- Serum calcitonin and CEA: Baseline tests will help during follow up follow up. Serum calcitonin > 10000 pg/ml is associated with cancer spread to other parts of the body.
- 24 hour urine metanephrines and nor-metanephrines: Few patients will have hidden adrenal tumours with or without increased blood pressure. Operating on these patients without excluding these tumors can sometimes be catastrophic.
Do I need CT (computed tomography) scan
If your serum calcitonin is > 500 you will need a CT scan of the neck, thorax & abdomen to check for the spread of the disease to other parts of the body.
Do all patients with medullary thyroid cancer need genetic testing.
One in four will have genetic mutation and management of these patients is totally different from others. They are at high risk for developing other tumours. Their children may also be at increased risk for the same cancer.
What should I do if my genetic test is positive?
Positive Genetic tests are classified into three categories
- Highest risk mutation : (RET codon M918T mutation and MEN 2B)
- High risk mutation : (RET codon C634 mutation and RET codon A883F)
- Moderate risk mutation : (All mutation other than M918T, C634 & A883F)
If you are positive for the genetic mutation, you may be at increased risk for a type of adrenal gland tumour called pheochromocytoma. You will need regular clinical checkups in order to diagnose this condition as early as possible.
Around 30% of patients who are positive for the RET mutation, can develop increased calcium in the blood due to tumours in the parathyroid gland.
Both these conditions are completely curable.
My genetic test is positive. Will my children also develop this cancer?
Children of affected patients have a 50% chance of having inherited the mutation. Children of mutation positive patients need to undergo genetic testing to determine if they have inherited the mutation. In case they are found to be mutation positive, the following course of action is advised based on the exact type of mutation.
- Highest risk mutation: (RET codon M918T mutation and MEN 2B)
- Total thyroidectomy + lymph nodal dissection before one year of age
- High risk mutation: (RET codon C634 mutation and RET codon A883F)
- Total thyroidectomy + lymph nodal dissection before 5 years of age
- Medium risk mutation: (All mutation other than M918T, C634 & A883F)
- Routine follow up with ultrasound and serum calcitonin, if abnormal to go ahead with total thyroidectomy + lymph nodal dissection.
What is the best available treatment for medullary carcinoma of thyroid?
Surgery is the best treatment option, as it can cure the patient.
What is the type of surgery done for medullary thyroid cancer?
All patients with medullary thyroid cancer are treated surgically. The type of surgery depends on the extent of disease, local spread and the general health of the patient. All patients will require removal of the thyroid gland together with the lymph nodes of the central compartment of the neck (called central neck dissection). The lymph nodes from the side of the neck may need to be removed if found to be involved with the cancer (called lateral neck dissection).These procedures require an expert thyroid surgeon as complete removal of diseased tissue needs to be achieved, while at the same time concentrating on the integrity of surrounding structures such as the parathyroid glands and recurrent laryngeal nerves. The aim of an expert surgeon will also include maintaining a normal appearance of the neck, and keeping the scar as small as possible.
What is the role of medical management (tyrosine kinase inhibitors)?
Medicines like tyrosine kinase inhibitors are used when the disease has spread to other parts of the body and in very large and in-operable medullary carcinoma of thyroid.
How is advanced disease treated?
Advanced medullary thyroid cancer may extensively involve surrounding structures like the food pipe (esophagus), wind pipe (trachea) and pharynx. Production of biologically active substances by the tumour can cause symptoms like diarrhoea, flushing or breathlessness. Surgical resection of this tumour by an experienced surgeon is required in these patients. Extensive disease which has spread to distant organs requires treatment with chemotherapy or radionuclide therapy, depending on the condition of the patient.
What should I do if my disease has spread to other parts of the body?
If you have excessive tumour burden, than you will benefit from medications called tyrosine kinase inhibitors. Sorafenib and vandetinib are two medications of this group, currently available in India.
Other treatment options which can be tried are Gallium DOTATE therapy or MIBG therapy.
Follow-up of medullary thyroid cancer
Patients require regular follow up with an endocrinologist and an endocrine surgeon. Blood tests are done to look for proteins produced by these cancer cells. Levels of calcitonin and CEA (carcinoembryonic antigen) are checked every 3 to 6 months and based on these tests other investigations are done appropriately.
What is the expected cure rate and survival in patients with medullary thyroid cancer?
Patients with this rare cancer have lower cure rates than patients with papillary thyroid cancer. In patients with early stage medullary cancer, surgery results in complete cure. 10-year survival rates are 90% when all the disease is confined to the thyroid gland, 70% when the cancer has spread to cervical lymph nodes and 20% when the cancer is found in distant sites.