Children normally do not get thyroid cancer. It is usually older people who get thyroid cancer. If children in one area are getting a lot of thyroid cancer, epidemiologists ask whether there was radioactive iodine poisoning in the area. The Fukushima disaster in March 2011 was in effect such radioactive iodine poisoning in this region of Japan.
An area extending about 20 kilometers from the nuclear plant has been declared an exclusion zone. It is not surprising that now there are reports of thyroid cancers in the area of Fukushima. The most recent statistics released in August 2015 showed that 137 of those children monitored in the Fukushima area came down with thyroid cancer while the year before there were only 112 such cases (25 cases less). Elsewhere, the disease occurs in only about one or two of every million children per year. Overall the amount of thyroid cancers in the Fukushima area is 20 to 50 times of what would normally be expected in a population.
Experience from Chernobyl nuclear accident
We learnt from the Chernobyl nuclear accident in April 1986 that the latency period (time elapsed between exposure to radiation and the first cancer observations) was about 4 years. The most dominant type of thyroid cancer was papillary carcinoma, which is a more benign type of cancer. Genetic examination of the tumors showed chromosomal rearrangements.
It is interesting to note that in Belarus, which is quite a distance from Chernobyl (Ukraine) there was a wave of thyroid cancers that stemmed from the Chernobyl disaster.
In the period of 1987-2000 there were about 4,400 radiation-induced thyroid cancers that appeared in Belarus; of these 692 cancers were among children and 3,709 cancers were among adolescents and adults.
How is thyroid cancer diagnosed?
Thyroid nodules can easily be detected by ultrasound examination. Normally in children there are no nodules in the thyroid gland, but it is out of nodules in the thyroid that thyroid cancer develops. If a thyroid nodule is detected in a child, the child needs to be referred to a specialist for further examinations and tests.
Treatment of thyroid cancer
What can be done to minimize the impact of thyroid cancer?
When the Fukushima disaster occurred, a lot of people and children were offered potassium iodide pills to take. The iodide saturates the body’s iodine receptors with non-radioactive iodine so that radioactive iodine from inhaled air would not enter the thyroid and lead to mutations of the thyroid tissue. We know from the atom bomb in Nagasaki that this type of prevention has helped to prevent the development of some thyroid cancers. Unfortunately not everyone after the Fukushima disaster took these iodide pills or they stopped taking them after a while, which allowed radioactive iodine to enter the thyroid glands of those exposed to the substance.
An unprecedented ongoing screening program of almost the entire children population in the Fukushima area is diagnosing thyroid follicles early. This has helped the medical teams to diagnose the thyroid cancers early and continue to follow these children. In the case of thyroid cancer treatment could be administered early before the cancer metastasized. If hypothyroidism occurs, this is treated right away with thyroid medication.
Long-term follow up after Hiroshima and Nagasaki
Previous experience with patients affected by the atom bombs in Hiroshima and Nagasaki, Japan in 1945 has shown interesting findings 55 to 58 years later. A total of 4091 (1352 men and 2739 women) people were followed. 14.6% of them had solid thyroid nodules; 2.2% of them had malignant thyroid tumors; 4.9% of them had benign thyroid nodules, and 7.7% had thyroid cysts.
Thyroid antibodies in the blood were also determined: 28.2% had positive thyroid antibodies, 3.2% had antithyroid antibody-positive hypothyroidism and 1.2% had Graves disease (=hyperthyroidism with enlarged thyroid). There was a significant linear dose-response curve between exposure to radiation and the amount of solid nodules, malignant tumors, benign nodules and cysts that had developed over the years in the 4091 men and women.
These types of long-term follow-ups help to know how important it is to follow all of the exposed individuals from the Fukushima disaster in a similar fashion.
A massive screening program is going on in children who were exposed to radioactive iodine in the Fukushima region. Nodules in the thyroid that are precursors to thyroid cancer are being evaluated. As a result early biopsies and, if necessary, resection of suspicious thyroid gland areas can be done before thyroid cancer or metastases develop. Physicians now build on the experience of prior nuclear disasters like the atom bombs in Hiroshima and Nagasaki and the nuclear accident in Chernobyl. Apart from radioactive iodine there were other nuclear isotopes that were released in these nuclear incidences. They may have been responsible for other malignancies that have developed in children, men and women in these areas.