Radioiodine Complications

Acute complications of therapy with I-131 are mostly nonsevere and usually short-lived. The more usual symptoms include sialoadenitis, radiation thyroiditis, neck edema, nausea, and gastritis (95). The salivary glands concentrate iodine and sialoadenitis may occur in about 30% of patients treated with radioiodine (96). It is characterized by pain, tenderness, and swelling of the salivary glands. Some patients suffer from reduced salivary gland function for more than one year after therapy with I-131. The use of lemon juice or lemon candies and abundant water ingestion reduces the incidence and severity of sia-loadenitis and reduces absorbed radiation dose to the salivary glands. Recently, a study indicated that an early start of sucking lemon candy may provoke an increase in salivary gland damage suggesting that lemon candy should not be given until 24 hours after therapy with I-131 (97). The use of amifostine may reduce significantly the damage to salivary glands, mainly when high doses are administered (98). Radiation thyroiditis and neck edema (99), when symptomatic, are usually treated with nonsteroidal anti-inflammatory drugs, or with steroids in the rare patient with more severe symptoms. Abundant liquid ingestion should always be encouraged; this augments the urinary flow output and decreases the radiation burden to the urinary bladder and the whole body. Gastrointestinal symptoms may be treated with antiemetics (nausea) and antacids (gastritis). Thyroid storm due to the release of large amounts of thyroid hormones occurs rarely in patients with extensive follicular metastases, usually within 10 days after treatment (76). Rarely, patients with brain metastases may develop edema and hemorrhage. Late effects include transitory decreased white blood cells, oligospermia, and transient ovarian failure. Infertility is rare except after high doses. There is no evidence of increased risk of congenital abnormalities (100). Patients with diffuse pulmonary metastases may rarely develop pulmonary fibrosis after radioiodine treatment.

Over the long-term, radioiodine therapy may be associated with development of secondary malignancies, such as acute myelocytic leukemia, usually occurring between 2 and 10 years after therapy. The risk increases in patients above the age of 50 who have received a dose of 37 GBq (1 Ci) of I-131 or more and is greater when this dose had been given over a short period of time (6 to 12 weeks). The risk is considerably lower when the total blood dose per treatment is less than 2 Gy (101). Increased prevalence of cancers of the urinary bladder, salivary gland, colon, and female breast has also been reported in patients, but with little agreement on the degree of absolute risk (101,102). Cumulated activities of more than 37 GBq (1 Ci) can also result in myelode-pression with a decrease in blood cell components, the risk increasing with the administered activity.

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