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Thyroid cancer has high survival rate

Treatments after surgery continue throughout life

Each year, more than 11,000 people – most of them women – are diagnosed with thyroid cancer in the United States. Treatment for thyroid cancer is generally successful, with many people living their expected lifespan physically unaffected by cancer.

The thyroid produces thyroid hormone to regulate metabolism. The four types of thyroid cancer have different outcomes, however. The most common type, papillary thyroid cancer, also is the most benign. Nearly 80 percent of people with thyroid cancer have papillary thyroid cancer. The other three types of thyroid cancer, follicular, medullary and anaplastic, are significantly less common and generally more severe.

Some thyroid cancer has a genetic link, said Aron Adkins, M.D., an endocrinologist at Marshfield Clinic Eau Claire Center. An endocrinologist is a physician who specializes in treating people with diseases that affect glands. Glands – such as the pancreas and thyroid – produce hormones that control development, metabolism and other factors. Together, the group of glands is the endocrine system.

People who were exposed to radiation, such as that used to treat cancer in childhood, are at greater risk for thyroid cancer as adults, he continued. “This is not diagnostic X-ray or visits to the dentist that we’re talking about,” he explained. Most thyroid cancer is spontaneous, meaning there is not a genetic link or a known cause.

Cancer often is found during a physical exam of the thyroid, a small, butterfly shaped gland on the front of the neck. A physician can feel a nodule on one of the lobes – the part that makes up the butterfly’s wings – during an exam. A person may also have a hard time swallowing or may find a nodule on themselves, Dr. Adkins said.

Some people have no symptoms with thyroid cancer and their cancer is discovered incidentally, through an ultrasound of a carotid artery, for example.

Because thyroid nodules are relatively common, a needle biopsy is used to confirm cancer. Nodules do not become cancer, said Alan McKenzie, M.D., an endocrinologist at Marshfield Clinic Marshfield Center. “They either are cancerous, or they are not,” he said.

For most people with thyroid cancer, treatment has two phases. First, the thyroid is completely removed. “We remove the thyroid completely for two reasons,” said Steven Standiford, M.D., a surgical oncologist at Marshfield Clinic Marshfield Center. “First, a fair number of thyroid cancers have more than one part of the gland. We may only be able to feel a nodule on one side, but often when we remove the thyroid, we find cancer elsewhere.”

The second reason surgeons remove the thyroid completely is that the second phase of treatment, radioactive iodine, attacks thyroid tissue in the body and would attack the thyroid left behind. Thyroid cells and thyroid cancer cells are the only tissues in the body that absorb iodine, making radioactive iodine a “smart bomb” treatment for thyroid cancer, Dr. Standiford said. “Any thyroid tissue left – and some is almost always left – is attacked by the radioactive iodine, as are any thyroid cancer cells that may be around. If there is a large amount of thyroid tissue remaining, there is less of the radioactive iodine to go where it is really needed – to attack the cancer cells. Other tissues throughout the body are left unaffected.”

It is important to remove thyroid tissue because thyroglobulin, a tumor marker that can be used to monitor a person after cancer, also is made by normal thyroid tissue. “If we remove the thyroid, and kill what is left, then we know if thyroglobulin appears later, it is related to cancer and we can treat it quickly,” Dr. Adkins said.

Treatment is often successful. A young person with papillary thyroid cancer can expect to live as long after surgery as she or he would have lived without cancer, Dr. Standiford said. “Sometimes, we will find cancer later in a lymph node in the neck,” he said. “Even with that, if it is removed, expected lifespan is the same as without ever having had cancer.”

Other types of thyroid cancer are less benign. In fact, anaplastic thyroid cancer is one of the most aggressive cancers known, Dr. Adkins said. Medullary thyroid cancer often is genetically linked, and children with the gene for the cancer may undergo a thyroidectomy at a very young age, Dr. McKenzie said.

People take a replacement hormone after surgery to regulate metabolism. “It’s generally thought that the body does not know the difference between synthetic thyroid hormone and the real thing,” Dr. Adkins said. “This is actually the easiest endocrine gland function to replace because it is a long-acting hormone and levels do not change much from day to day.”

This hormone is different from hormone replacement therapy women may take after menopause and it does not have the same risks associated with it.

The pituitary gland controls the amount of hormone the thyroid gland produces by secreting thyroid stimulating hormone. Because thyroid cancer is stimulated by thyroid stimulating hormone, more replacement thyroid hormone is given than the body would naturally call for to suppress thyroid stimulating hormone. “We want to suppress thyroid stimulating hormone for the rest of a person’s life,” Dr. Adkins said.

One risk of surgery is accidentally removing the parathyroids, four tiny glands that control calcium absorption. “If at all possible, we preserve the parathyroids during surgery to avoid complications later,” Dr. McKenzie said. In fact, just one parathyroid likely could control calcium levels if necessary, but physicians prefer to save all four if possible.

Once a person has had his or her thyroid removed, regular follow-up is required. An endocrinologist looks for any cancer that recurs, monitors bone density and makes sure thyroid hormone levels are appropriate.

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