Chernobyl 30th Anniversary and the Thyroid Cancer Connection

This spring marks the 30th anniversary of the Chernobyl nuclear accident and brings renewed attention to long-term health impacts of the event. 

The accident took place on April 26, 1986 in northern Ukraine near Belarus. The reactor at Chernobyl had an archaic design and lacked a containment dome. The winds carried massive amounts of radiation over a large area of northern Europe. The substances released included many types of radioactive materials, including iodine 131. 

A large increase in childhood thyroid cancer in areas near Chernobyl began 4 years after the accident. The time from exposure was shorter than the 10 years or more that had previously been assumed for developing radiation-related thyroid cancer. 

The children lived in northern Ukraine, Belarus, and western Russia at the time of the accident. In Belarus, 333 children were diagnosed between 1986 and 1994, compared to only 7 children in the 9 years before the Chernobyl accident. The main source of exposure was considered to be the children’s consumption of fresh cow’s milk containing radioactive iodine from the fallout, which fell onto the grass that the cows ate. 

Between 1990 and 2002, more than 4,000 Chernobyl-area children had been diagnosed with differentiated thyroid cancer, the type resulting from the I-131 fallout. A 2013 article from Memorial Sloan-Kettering Cancer Center estimated that 6,000 cases of thyroid cancer had been caused by the Chernobyl disaster. 

“The risk of developing thyroid cancer is especially high among children younger than 10 at the moment of radiation exposure,” wrote James John Figge, MD, in the reference book Thyroid Cancer: A Guide for Patients.

Genomic Study 

In 2013, an international study, led by James Fagin, M.D., of Memorial Sloan-Kettering Cancer Center, reported on the first comprehensive genomic analysis from patients who developed thyroid cancer after exposure to radiation from Chernobyl. The findings were reported in the Journal of Clinical Endocrinology and Metabolism. 

Most of the patients were under age 10 at the time of the Chernobyl accident and had developed thyroid cancer as adolescents or young adults. The study’s findings reveal two important things,” said Dr. Fagin In an interview for a MSKCC publication. “One, that radiation causes a particular type of genetic damage that is associated with characteristic cancer genes; and two, that those genes turn on the activities of pathways that are critical for the formation of thyroid cancer.” 

Risk Study 

In another study, an international research team led by the National Cancer Institute (NCI), part of the U.S. National Institutes of Health, found a clear dose-response relationship, in which higher absorption of radiation from the Chernobyl fallout of I-131 led to an increased risk for thyroid cancer. The risk had not appeared to diminish as of 2011. 

The study represented the first prospective examination of thyroid cancer risk in relation to the I-131 doses received by Chernobyl-area children and adolescents. Results appeared in the journal Environmental Health Perspectives on March 17, 2011. 

The researchers found that the cancer risk continued for those who had lived in the Chernobyl area at the time of the accident.  However, a previous analysis of atomic bomb survivors and medically irradiated individuals had found that cancer risk began to decline about 30 years after exposure, although it was was still elevated 40 years later.  

Therefore, the researchers believed that continued follow-up of the participants in the Chernobyl study would be needed to determine whether a decline in the risk level is likely. 

Looking Ahead—Awareness for Early Detection 

Because thyroid cancer is usually treatable when found early, ThyCa: Thyroid Cancer Survivors’ Association, Inc. invites people to help raise awareness of thyroid cancer and to ask their physician to do a neck check during a routine medical appointment. A neck check takes only a minute. 

Most thyroid nodules are benign, not cancer. Signs to discuss with the physician include a lump in the neck, lymph node swellings, fullness in the neck, voice changes that persist, or difficulty breathing or swallowing. 

ThyCa sponsors Thyroid Cancer Awareness Month, the worldwide observance, each September, as well as year-round awareness campaigns. 

Free awareness and education materials are available from ThyCa at any time, by emailing to thyca@thyca.org or by downloading publications from the Raise Awareness page. http://www.thyca.org/how-to-help/awareness/ 

For More Information

• Study Reveals Genetic Causes for Thyroid Cancer Increase after Chernobyl 
• Higher cancer risk continues after Chernobyl 
• Joshua’s Story: From Pediatric Thyroid Cancer Family Stories
• Potassium Iodide and the Thyroid Gland: Interview with Kenneth D. Burman, M.D., Endocrinologist