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Thyroid cancer is a rare disease in most countries and the risk usually
being twice as high in women as for men. The prognosis for thyroid cancer
is good with an overall 10-year relative survival rate of approximately
90% and age at diagnosis, sex, stage, and histopathology are all factors
of prognostic value (25,26).
The small number of thyroid cancers limits the possibility to study the risk of subsequent cancers. Record linkage studies of thyroid cancer patients, without knowledge of given therapy, have shown increased risks for a subsequent cancer of the female breast, colon, urinary tract, thyroid gland, and connective tissue (27,28). Brincker et al. (29) followed 194 patients with an 131I treated thyroid cancer and found 2 myeloid leukemias compared to 0.097 expected (Table 1). Edmonds and Smith (30) followed 258 thyroid cancer patients treated with 131I and found increased risks of breast cancer, bladder cancer, and leukemia (Table 1). In a German study of 298 patients an increased overall risk of 1.94 (95% CI 1.35-2.70) and elevated risks of bladder cancer and leukemia were found (Table 1) (31). A Swedish follow-up study of 1,955 thyroid cancer patients, 834 given 131I therapy, showed an increased risk of cancer in the salivary glands (n=3), female genital organs (n=18), kidney (n=7), and adrenal glands (n=2) among those 131I exposed (Table 1) (32). No increased risk of bladder cancer or leukemia was found and no increased risk with administered amount of 131I or time since exposure was noted arguing against a radiation effect. For those 1,121 thyroid cancer patients not given 131I, an increased risk of a subsequent cancer in the adrenal glands (n=5) was found. |
