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More thyroid cancers are diagnosed every year—in the U.S., the occurrence of thyroid cancer has tripled in the last 30 years. According to the U.S. Centers for Disease Control and Prevention, about 33,000 women and 12,000 men are diagnosed with thyroid cancer each year, and about 905 men and 1,100 women die from the disease annually.
While many of these cancers are small and less advanced, we’re also seeing more large, advanced thyroid tumors that require treatment.
Some of this increase in diagnoses may be due to better early detection and advancements in diagnostic technologies such as ultrasound and needle biopsy. But researchers are investigating the root causes of these cancers—and whether viruses known to cause cancer, such as human papillomavirus (HPV), could be to blame.
Thyroid cancer is the most common endocrine cancer, and it can disrupt the function of the thyroid—a butterfly-shaped gland in the neck that secretes metabolism-regulating hormones into the bloodstream. These hormones help control breathing, heart rate, the nervous system, menstrual cycles, body temperature, and more.
Overall, thyroid cancer is highly treatable. About 98% of patients with thyroid cancer survive more than five years after diagnosis. However, if we can pinpoint and prevent the cause, we can spare more patients from the symptoms and associated side effects of treatment.
Exploring causes of thyroid cancer.
The exact cause of thyroid cancer is not yet known. In thyroid tissues and tumors, researchers have found the DNA of some viruses, including herpes, two hepatitis viruses, human T cell lymphoma virus, and HPV. These viruses have not been confirmed to be associated with the onset or progression of thyroid cancer.
However, HPV is associated with other types of cancer.
There are more than 200 forms of HPV, some of which are spread through sexual contact. While low-risk HPVs can cause warts around the genitals, high-risk HPVs causeabout 3% of cancers in women and 2% of cancers in men, including those of the cervix, anus, genitals, and throat. Oropharyngeal (throat) cancers are the most common HPV-related cancers in the U.S. Getting the HPV vaccine can prevent HPV infection and can reduce the risk of developing cancers associated with the virus.
While HPV particles are found in 3-5% of patients with benign thyroid nodules, thyroid dysfunction or thyroid cancer, HPV has not been proven to cause dysfunction or cancer in the thyroid gland. However, research in animal models suggests it’s worth continuing to search for a possible association.
Known causes of thyroid cancer.
Research has revealed several risk factors for developing thyroid cancer, such as:
- Genetic conditions inherited from your family.
- Smoking tobacco, obesity, and using ethanol.
- Environmental exposure to hazards such as nonmedical radiation.
The Chernobyl nuclear disaster in 1986 released a significant amount of radioactive material, about 4,000 cases of thyroid cancer were diagnosed in children under age 18 in nearby eastern European countries—a rate far higher than normal. However, exposure to modern medical radiation used for imaging such as X-rays or CT scans has not been shown to significantly increase the risk of thyroid cancer.
Developing the best treatment for thyroid conditions starts with knowing what type of cancer—if any—is present in the gland. That’s why we work closely with pathologists to help understand each patient’s individual circumstances.
Diagnosing thyroid conditions and cancers.
Most patients with thyroid cancer first see their primary care provider due to symptoms such as:
- A lump or swelling that can be felt through the skin at the front of the neck
- Difficulty breathing or swallowing
- Pain in the neck and throat
- Swollen lymph nodes in the neck
- Voice changes such as hoarseness
An endocrinologist can help determine the cause of their symptoms. Some patients have thyroid dysfunction but not cancer. An overactive thyroid gland, called hyperthyroidism or Graves’ disease, can cause symptoms like nervousness, weight loss, heart palpitations, and trouble swallowing.
Hypothyroidism, in which the thyroid does not make enough hormones, cause symptoms such as fatigue, weakness, and inability to concentrate. A thyroid function test can help understand the source of these symptoms and indicate treatment.
About 60-70% of the patients who are referred to us have a common condition called a thyroid nodule. Most of these are small, benign, and will never cause any symptoms. We can perform an ultrasound to take sound-wave images of the thyroid gland and nodules so we can examine the thyroid without surgery.
Nodules larger than 1 – 1.5 centimeters can sometimes be cancerous. In these cases, we perform a fine needle aspiration biopsy. The doctor uses a thin needle to remove a sample of cells from the nodule which are then examined under a microscope for signs of cancer. We study cancers on the molecular level because it’s important to rule out more aggressive types, which can be significantly more complicated to treat.
About 75% of thyroid cancers are a slow growing, less invasive type called papillary cancer. Usually found in only one lobe in patients 50 and younger, this type typically grows slowly and can spread to the lymph nodes. Less common types of cancer include:
- Follicular: Representing about 10% of thyroid cancers, this type of cancer grows slowly and can spread to the lymph nodes and other parts of the body.
- Hurthle cell: This cancer is rare and aggressive, and it is likely to spread to lymph nodes, the neck, and beyond.
- Medullary: This type accounts for about 3% of all thyroid cancers. It occurs when the gland’s cells that produce hormones, called C cells, become cancerous.
- Anaplastic: Making up only about 1% of thyroid cancers. This type grows fast and can be difficult to treat. It occurs most often in people over 60 and can cause sudden symptoms such as neck swelling that can lead to difficulty breathing.
Be sure to talk with your doctor if you experience symptoms because although we’re not sure what causes thyroid cancer, we believe that early treatment is better.
In recent years, literature and conversation in our field has centered on the overdiagnosis or overtreatment of thyroid cancer. This is because many patients with papillary thyroid cancer have good outcomes, leading some endocrinologists to recommend monitoring instead of surgery. Our view is that it is better to diagnose and treat thyroid cancer early. We believe earlier is better for cancer surgery, and we believe it is our imperative to understand as much as we can about an individual patient’s cancer so everyone involved can make an informed decision about treatment.
Treatment options for papillary thyroid cancer.
Based on the results of these tests, we recommend surgery for virtually all thyroid nodules that harbor cancer. Surgical options include removing the entire thyroid gland or only one of the thyroid’s two lobes. This procedure, called thyroid lobectomy, has benefits including a lower risk of and complications less frequent need for hormone replacement therapy because a portion of the gland it left intact.
Our very experienced surgeons at MedStar Washington Hospital Center perform about 800 thyroidectomies a year. This procedure usually involves removing the gland through a small incision in the neck while the patient is asleep under anesthesia. Some patients spend one night in the hospital, while others return home the same day.
Some patients may be eligible for thyroidectomy without an incision in the neck. Using an advanced procedure called transoral endoscopic thyroidectomy, we can remove the thyroid gland through the mouth, which results in no scarring and minimal side effects. Not all patients qualify for this approach, as small nodules are best suited for this procedure.
Because the thyroid gland absorbs iodine, radioactive iodine has been a targeted therapy for thyroid cancer for more than 70 years. When injected radioactive iodine is taken up by the gland, the radiation works to destroy thyroid tissue, including cancerous cells. In fact, radioactive iodine therapy is so effective it can even remove thyroid cancer cells that have spread to other parts of the body.
Some patients with metastatic thyroid cancer do not respond well to radioactive iodine treatment. For those patients, we use molecular testing to help determine the best course of treatment, which can include oral chemotherapy to help slow or stop the progression of the disease.
We also work closely with an expert radiation oncologist to help determine the best treatment for each patient. External radiation therapy can help treat metastatic cancer that has progressed to large areas such as the bones, liver, or lungs.
For this effective treatment, medication reduces the expression of thyroid hormones from the pituitary gland to prevent cancer from coming back.
Team-based treatment for the best outcomes.
At MedStar Washington Hospital Center, patients benefit from our team-based approach to thyroid cancer treatment. Every patient’s case is reviewed by thyroid surgeons and specialists in radiation oncology, nuclear medicine, and ear, nose and throat care, and oncology Together, we review develop the best care plan for each patient.
Research is underway throughout the world to help better understand the increase of thyroid cases and what causes it—including whether viruses such as HPV are to blame. In the meantime, we continue to focus our efforts on helping each patient achieve the best possible treatment outcome.