The earliest clinical use of radioiodine in the treatment of thyroid cancer was reported by Hamilton in 1940. Since those early days dramatic responses and cures have been documented even in disseminated tumors, establishing iodine as the most effective non-surgical treatment for thyroid cancer . Most adult patients with tumors greater than 1 cm will be treated with an ablation dose (usually 3-3.7 GBq, 81-100mCi) of 131I while those with adverse prognostic factors or metastatic disease will need to receive several doses of radioiodine. The safety of 131I is well documented . Acute toxicity is mild - side effects include nausea, sialoadenitis, neck discomfort, and transient hematological depression. Late complications such as pulmonary fibrosis, myelodysplasia, leukemia, and second malignancies are rare. The risk of leukemia and possibly second cancers increases with high cumulative dose of 131I .
Differentiated thyroid cancer is not uncommon in women of childbearing years or in young men, and can also affect children, particularly those previously exposed to radiotherapy to the head and neck. For this group of patients prognosis is excellent with a long-term survival of over 90% . In recent years the possibility of long-term gonadal damage from radioactive iodine has become increasingly appreciated and the subject of several reports.
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