Noteworthy Numbers: Thyroid Cancer

TON - March 2017, Vol 10, No 2 - Noteworthy Numbers

The thyroid is a butterfly-shaped endocrine gland that produces hormones essential in maintaining normal heart rate, blood pressure, body temperature, and metabolism. Thyroid cancer represents only 3.8% of new cancer cases annually in the United States, but occurs approximately 3 times as often in women as in men.1,2 The following information about thyroid cancer may prove helpful.

There are 4 types of thyroid cancer: papillary, seen in 70% to 80% of patients; follicular, including Hürthle cell cancer, seen in 10% to 15%; medullary, seen in 5% to 10%; and anaplastic, the least likely to respond to treatment, which affects <2%.1 In the United States, an estimated 64,300 new cases of thyroid cancer were diagnosed in 2016 (49,350 in women, and 14,950 in men) and approximately 1980 deaths occurred because of the disease (1070 in women, and 910 in men).2

Thyroid cancer is commonly diagnosed in patients with a family history of the disease, or in those exposed to radiation of the thyroid.3 It becomes more common with age: the papillary type can occur at any age, but is most often diagnosed between ages 30 and 60 years; most cases of follicular and medullary cancers are diagnosed between ages 40 and 60 years; and anaplastic thyroid cancer usually occurs after age 65 years.1

Several issues regarding the diagnosis and treatment of thyroid cancer are being debated. The US Preventive Services Task Force issued a draft statement in December 2016 recommending against routine screening of asymptomatic patients. In response, ThyCa: Thyroid Cancer Survivors’ Association listed 9 statements on its website in defense of palpation—including that it is quick, uses no special equipment, and incurs no additional cost. Further analysis of nodules larger than 1 cm to 1.5 cm was recommended.4 The International Agency for Research on Cancer reported “an epidemic of thyroid cancer overdiagnosis” from 1987 to 2007, and estimated that current overdiagnosis in women accounts for 70% to 80% of cases in the United States.5

Researchers at Duke University studied the number of lymph nodes requiring assessment to “truly be certain of the risk of occult disease,” and concluded that in a patient with a 1-cm to 2-cm tumor, the removal of 6 lymph nodes that tested negative would yield 90% confidence that the cancer had not metastasized. Increased size of the tumor would require removal of more lymph nodes; 9 nodes for a 2-cm to 4-cm tumor, and 18 nodes for a tumor >4 cm.6

References
1. Brady B. Incidences and types of thyroid cancer. EndocrineWeb. Updated July 6, 2016. www.endocrineweb.com/guides/thyroid-cancer/incidence-types-thyroid-cancer. Accessed February 2, 2017.
2. American Cancer Society. Cancer facts and figures 2016. www.cancer.org/research/cancer-facts-statistics/all-cancer-facts-figures/cancer-facts-figures-2016.html. Accessed February 2, 2017.
3. American Cancer Society. Thyroid cancer risk factors. Updated April 15, 2016. www.cancer.org/cancer/thyroid-cancer/causes-risks-prevention/risk-factors.html. Accessed February 2, 2017.
4. ThyCa: Thyroid Cancer Survivors’ Association. Thyroid screening: ThyCa’s comments on the USPSTF draft recommendations. http://thyca.org/news/USPSTFcomments012017. Accessed February 2, 2017.
5. Jenkins K. Thyroid cancer overdiagnosis in half a million patients. August 18, 2016. www.medscape.com/viewarticle/867598. Accessed February 2, 2017.
6. Horvath K. Setting limits: lymph node removal & thyroid cancer. January 2017. http://endocrinenews.endocrine.org/setting-limits-lymph-node-removal-thyroid-cancer. Accessed February 2, 2017.

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Last modified: March 14, 2017