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The Risk Factors for Medullary Thyroid Cancer



Medullary thyroid carcinoma may be one of the less common kinds of thyroid cancer, accounting for only 4% of the total thyroid cases in the United States. However, that still translates to 1,000 cases diagnosed every year. With most cases only diagnosed by Stage IV and a 28% survival rate at that stage, it is important to know more about this cancer, especially its only known risk factor: genetics.

An Unwanted Inheritance

Unlike other cancers, which are related to smoking or environmental factors, genetics is so far the only known risk factor for medullary thyroid cancer. And unfortunately, only 25% of cases are said to be associated with this risk factor. There are also no identified links to age.

For the remaining 75%, which fall under the sporadic or isolated medullary thyroid cancer category, current research has not yet uncovered any causes or additional risk factors. As Dr. Manisha H. Shah, a medical oncologist at the Ohio State University Comprehensive Cancer Center, said in a April 2015 interview with Medscape: “Basically, we don’t really know why they occur.”

Due to this risk factor, those who are diagnosed with medullary thyroid cancer and their immediate family are advised to get genetic testing right away. It comes in the form of a simple blood test that scans for the rearranged during transfection (RET) proto-oncogene mutation. This paradigm for targeted therapy was pioneered by the M.D. Anderson Cancer Center in 2009; today, test is available in many major medical centers, such as Providence Saint John’s Health Center in California.

Once the mutation is detected, doctors can now make various predictions. These include the likelihood of developing the cancer, the age of onset, and the aggressiveness of the disease.

In the same interview, Dr. Shah explains: “It’s very clear that if you have the gene, you’re going to get the cancer. It’s only a matter of at what age and how aggressive the cancer will be.”

On Diagnosis and Treatment

Since there is no other known risk factor for medullary thyroid cancer, keeping an eye out for this disease is the name of the game. While many cases are asymptomatic, one of the few manifestations of this ailment is a lump in the neck that does not disappear after an extended period of time. Another symptom is chronic diarrhea or flushing, which is triggered by the hormones produced by cancerous mass.

Meanwhile those who have the mutated gene, but have not yet developed the cancer, are evaluated and may be advised to get a prophylactic thyroidectomy. In layman’s terms, this is a surgical procedure designed to remove all or part of a thyroid gland, preventing the mutation from developing into cancer.

And for those who do have medullary thyroid cancer, two tyrosine kinase inhibitors (TKIs) are used to treat the disease: vandetanib and cabozantinib. While both treatments are deemed effective, they lose effectiveness after two years. Various treatments are still undergoing clinical trials.

With various improvements in recent years concerning diagnosis, plus other treatments in the pipeline, it is not far-fetched to say that a better way to handle medullary thyroid cancer will be available in the future.