The highest incidence rates for thyroid cancer in the SEER regions occur in women, particularly in the Pacific Island and Southeast Asian populations living in California and Hawaii. Mortality rates are lower than incidence rates by a factor of about five to ten in men and eight to twenty in women. Although women have three-fold higher incidence rates than men, the gender difference for mortality is smaller, reflecting somewhat better survival rates for women than for men. Most deaths due to thyroid cancer occur in the older age groups and may occur more than ten years after diagnosis. Thyroid cancers occur in all age groups.
Many studies report an association between thyroid cancer and radiation exposure.
In the 1930s and 1940s, X-rays were often used in the treatment of skin diseases and other benign conditions such as enlarged thymus or tonsils. Increased risks have been described in Japanese atomic bomb survivors and in persons exposed to fallout from atomic testing in the Marshall Islands. Populations exposed to radioactive fallout from the nuclear processing facility in Hanford, Washington and from the vicinity of the Chernobyl nuclear plant disaster in the Ukraine are currently being studied. Goiter and other thyroid diseases, as well as diets high or low in iodine, have been suspected risk factors. Miller BA, Kolonel LN, Bernstein L, Young, Jr. JL, Swanson GM, West D, Key CR, Liff JM, Glover CS, Alexander GA, et al.