About Thyroid Cancer

Newly diagnosed thyroid cancer patients find that there is a lot to learn about our unique cancer.  Often patients don't initially know the function of the thyroid gland, its location in the body, how they will get along without having this organ, or what will happen in their treatment.  All of this is quite typical for people getting this diagnosis.  

This section of this website will outline some of the facts and let you know what path your treatment will likely take.

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Who Gets Thyroid Cancer?

  • the literature varies, but it is estimated that at least half of the population has thyroid nodules
  • 95% of thyroid nodules are benign
  • 80% of those with thyroid cancer are women (CCS Stats)
  • thyroid cancer is now the #1 cancer in incidence in young Canadians (CCS 2013)

Risk Factors

  • History of thyroid cancer (pre-occuring, or in other family members)
  • Age (higher risk over 45 years old)
  • Gender (more common in women but slightly higher risk of aggressive disease in males)
  • External beam radiation (for other cancers)

For the vast majority of individual patients, the cause of thyroid cancer is unknown. 

The only known association (in a small number of cases) is direct exposure to high levels of radiation, such as for those living in the area of the Chernobyl Nuclear Reactor accident in 1986.

It is also not known why the ratio of women with thyroid cancer in relation to men with the disease is very imbalanced. 80% of patients with the disease are women (CCS 2013).  Thyroid cancer has one of the lowest death rates among cancers (less than 1% for differentiated disease).  However, men are more at risk if they do have the disease, as they make up 20% of the cases but 37% of the deaths from this particular form of cancer.

The comparative incidence rate across provinces in Canada also varies greatly.  The highest incidences, as reported by the Canadian Cancer Society (2013), are in the provinces of Ontario, Quebec and New Brunswick.  Some have hypothesized that environmental influences have played a part in the distribution of the disease.  Others purport theories of unequal access to expert diagnosticians. However, no definitive research has been undertaken to explain the geographic differences.


To View Related Research Studies Regarding Thyroid Cancer Incidence, see the following:

Yoo et al: Characteristics of Incidentally Discovered Thyroid Cancer JAMA Otolaryngol Head Neck Surg. Published online October 10, 2013. doi:10.1001/jamaoto.2013.5050 http://archotol.jamanetwork.com/article.aspx?articleid=1748769

Brito et al: TOO MUCH MEDICINE, Thyroid cancer: zealous imaging has increased detection and treatment of low risk tumours, BMJ 2013;347:f4706 doi:  August 2013 http://www.thyroidcancercanada.org/userfiles/files/Brito_Zealous_Imaging.pdf

Smith JJ et al: Cancer after thyroidectomy: a multi-institutional experience with 1,523 patients. J Am Coll Surg 2013;216:571-9. There is an up to 18% chance that pathology testing post-surgery on a goiter will indicate thyroid cancer. http://www.thyroidcancercanada.org/userfiles/files/Smith_TC_in_Goiters.pdf

Li, Nan et al: Impact of Enhanced Detection on the Increase in Thyroid Cancer Incidence in the United States: Review of Incidence Trends by Socioeconomic Status Within the Surveillance, Epidemiology, and End Results Registry, 1980–2008.  Varying access to health care (eg. FNA) does not explain the increase in incidence, ie. more cases not due to findings of 'incidentalnomas' http:www.thyroidcancercanada.org/userfiles/files/access_to_care_not_explanation_for_rise_in_TC_journal_article.pdf

Hershman, J: Socioeconomic Status and Access to Care Do Not Account for the Rising Incidence of Thyroid Cancer, Clin Thyroidol 2013;25:66–67. (Summary of the Li et al findings above).  Varying access to health care (eg. FNA) does not explain the increase in incidence, ie. more cases not due to findings of 'incidentalnomas' http://www.thyroidcancercanada.org/userfiles/files/access_to_care_not_explanation_for_rise_in_TC.pdf

Chen AY et al: Increasing incidence of differentiated thyroid cancer in the United States, 1988-2005. http://www.thyroidcancercanada.org/userfiles/files/Chen_increase_in_incidence.pdf

Enewold et al: The utilization of sensitive diagnostic procedures does not completely explain the observed increased incidence in papillary thyroid cancer over three decades, 2009 http://www.thyroidcancercanada.org/userfiles/files/Enewold_increase_in_PTC.pdf

Aschebrook-Kilfoy et al: Thyroid cancer incidence patterns in the United States by histologic type, 1992-2006 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3025182/?tool=pubmed

Levine et al: Study Underscores Importance of Physical Exams As Diagnostic Tool for Thyroid Cancer, News Release of AACE, May 3, 2013 Most cancerous nodules found in physical examination, or by patients themselves http://www.thyroidcancercanada.org/userfiles/files/Levine_incidence_study.pdf

TIME Magazine article "The Screening Dilemma", 2011 http://www.thyroidcancercanada.org/userfiles/files/TIME_Magazine_The%20Screening%20Dilemma.pdf

SELF Magazine, May 3013: "Thyroid Cancer: What Are Your Risks? If you feel a lump in your throat, you might not want to treat it. Hard to fathom, but it's true! Here's why."  A magazine article http;//www.thyroidcancercanada.org/userfiles/files/Self_magazine_does_thyroid_cancer_matter.pdf

Does the proximity to a nuclear reactor increase once chance of having TC? http://www.thyroidcancercanada.org/userfiles/files/Geographic_thyroid_cancer_USA.pdf

Canada Sees Mixed Trends in Thyroid Cancer (Study by Hall, S.) Initial tumour size corresponds with location of patient (ie. urban/suburban/rural) http://www.thyroidcancercanada.org/userfiles/files/Canada_Sees_Mixed_Trends.pdf

Davies & Welch: Increasing Incidence of Thyroid Cancer in the United States, 1973-2002. A study regarding rise in incidence (ie. contention that the rise is due to findings of "incidentalnomas") http://www.thyroidcancercanada.org/userfiles/files/Davies_Welch_Increase_in_TC_1973-2002.pdf

Kent et al: Increased incidence of differentiated thyroid carcinoma and detection of subclinical disease, CMAJ. 2007 November 20; 177(11): 1357–1361. http://www.thyroidcancercanada.org/userfiles/files/Kent_Increased_Incidence.pdf

Welch et al: Overdiagnosis in Cancer, 2010, J Natl Cancer Inst http://www.thyroidcancercanada.org/userfiles/files/Welch_Overdiagnosis%20in%20Cancer.pdf

Nilubol et al: Multivariate analysis of the relationship between male sex, disease-specific survival, and features of tumor aggressiveness in thyroid cancer of follicular cell origin. Thyroid 2013;23:695-702. Epub May 28, 2013. Study indicates that being male does not make TC more likely or agressive, but rather the authors suppose that diagnosis is made later therefore the patient has more aggressive disease. http://www.thyroidcancercanada.org/userfiles/files/Nilubol_men_with_TC.pdf

 

As well, an interesting finding is that persons of Filipino descent have a higher risk of being diagnosed with thyroid cancer than those in the general population of North America (Clark et al 2006, Haselkorn et al 2003, Rossing et al 1995). As well, those of Filipino descent have greater chance of recurrence (Kus et al 2010). As well, other USA studies (Aschebrook-Kilfoy, Enewold, Li, et al) indicate that those of Asian descent are more likely to be diagnosed with PTC and those who are of African-American origin are least likely to be diagnosed. Hispanics are more highly represented in the group who contracted medullary (MTC) or anaplastic (ATC).  Follicular (FTC) rates did not vary by ethnicity in these studies.

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