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January 28, 1974

Thyroid Cancer After lodine-131 Therapy

Author Affiliations

Stanford University Medical Center Stanford, Calif

JAMA. 1974;227(4):438. doi:10.1001/jama.1974.03230170054017

To the Editor.—  The patient of Kreps et al (226:774,1973) developed a papillary carcinoma of the thyroid 20 years after treatment of hyperthyroidism with iodine 131. Reports of this relationship, some of which the authors did not cite (Table) include only documented cases; almost certainly, others have gone unreported.Three factors about these patients are apparent. Six were less than 30 years of age at the time of treatment, an incidence higher than anticipated, since considerably more middle-aged and elderly patients receive radioiodine therapy. This argues strongly in favor of a conservative age limit (eg, 40 years of age) below which therapeutic radioactive iodine is prescribed only for especial reasons.The original dose of iodine 131 prescribed for six of the patients was less than 5.0 millicuries, probably insufficient to kill or sterilize the follicular cell population. The reason for the introduction of low-dose iodine 131 therapy was to eliminate