Thyroid Cancer Patients Face Increased Risk of Second Cancer

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Many people who have recovered after thyroid cancer are concerned about the risks of second cancers. A number of recent research studies have shown that thyroid cancer patients do face an increased risk of developing second primary cancer.

In a large review study published in the Journal of Clinical Endocrinology and Metabolism, almost 40,000 people who had primary thyroid cancer were evaluated for a period of up to 25 years.

The members of the study group were monitored, to assess whether they developed a second primary cancer. Almost 2000 people who had thyroid cancer, diagnosed after another primary cancer, were also evaluated.

The researchers determined that thyroid cancer patients face a 30 percent greater risk of second primary cancer when compared to the general population.

It is important to note that these are not metastases (a spread) of the initial thyroid cancer, but instead, are appearance of an entirely new type of cancer.

Specific Secondary Cancer Risks 

According to the research, the increased risk of secondary cancers includes cancers of the following organs and glands:

  • salivary gland
  • pharynx
  • stomach
  • small intestine
  • colon
  • rectum
  • bone
  • soft tissue sarcoma
  • non-melanoma skin
  • female breast
  • prostate
  • kidney
  • brain
  • adrenal gland
  • non-Hodgkin's lymphoma
  • leukemia
  • parathyroid gland

The risks of these cancers were different. 

One study published in 2013 in the journal Thyroid found that increased risks of developing one of these cancers after having primary thyroid cancer.

The risk depended on the different types of cancer studied. The level of risk was also related to the size of the initial thyroid cancer, and the use and dose of radiation to treat the thyroid cancer. The most common second cancers were cancers of the salivary gland and kidney. 

Research has also shown that thyroid cancer survivors are at increased risk for developing breast cancer, when compared with the breast cancer risks in the general population.

In particular, those women who are diagnosed with thyroid cancer after the age of 50 have a much greater risk for developing a second primary breast cancer. 

The risk of developing primary thyroid cancer is also significantly elevated in those who have other types of cancer. Specifically, those at greatest risk are people who have had cancer of the salivary gland, esophagus, stomach, colon, rectum, liver, pancreas, larynx, lung, bone, soft tissue sarcoma, melanoma, non-melanoma skin, female breast, cervical, uterine, ovarian, testicular, kidney, brain, adrenal, Hodgkin's disease, non-Hodgkin's lymphoma or leukemia.

Another study has found that treating children and young adults with radioactive iodine for thyroid cancer increases their risk of second cancers, especially salivary gland cancer. 

Experts theorize that the use of radioactive iodine—itself a carcinogenic treatment—may explain the increased risk of other cancers, but they also agree that the carcinogenic effects of the therapy can't explain all of the increased risks.

There are several other theories:

  • there is a shared genetic risk factor for these various cancers
  • there is a shared environmental risk factor for the various cancers 
  • there is a shared hormonal risk factor for the various cancers
  • various potentially carcinogenic therapies cause the second cancers

More research will need to be done to test these theories and develop more definitive information. 

What You Need to Know

Keep in mind that the overall risk of getting another cancer is only slightly higher if you have had thyroid cancer, compared to the overall population. Still, because there is some risk, you will want your physician to ensure that you are screened for the more common second primary cancers such as breast, prostate, and leukemia, during your followup period after thyroid cancer treatment.

 

In addition: 

  1. Physicians who are overseeing the health of patients with primary thyroid cancer should be aware of the risk of second primary cancers in their patients.
  2. Physicians who treat other cancer patients should remain aware of the potential for thyroid cancer in their patients.
  3. Patients who have had thyroid cancer should make their physicians aware of their medical history, and personally remain aware of their own increased risk of other cancers.

Source:

Aaron P, Brown J, et al. "The Risk of Second Primary Mfalignancies up to Three Decades after the Treatment of Differentiated Thyroid Cancer." Thyroid. 2007; 93 (2): 504-515. doi: 10.1210/jc.2007-1154

Kim C, Bi X, et al. "The risk of second cancers after diagnosis of primary thyroid cancer is elevated in thyroid microcarcinomas." Thyroid. 2013 May;23(5):575-82. doi: 10.1089/thy.2011.0406. Epub 2013 Apr 18.

Sandeep, Thekkepat C. et. al. "Second Primary Cancers in Thyroid Cancer Patients: A Multinational Record Linkage Study, J Clin Endocrinol Metab 2006 91: 1819-1825; first published February 14, 2006 as doi:10.1210/jc.2005-2009

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