Case 0006: Administration of Iodine-131 to a Pregnant Patient

Hello Brachyblast readers! We would like to once again thank those who provided feedback on case 0005. Such feedback is valuable and hopefully leads to prevention of reoccurrence. In this month’s BrachyBlast we present case 0006 which was reported to NRC in 1998. Please continue to share your thoughts as we work together to encourage safe brachytherapy/radiotherapy practices.

Case 0006: Administration of Iodine-131 to a Pregnant Patient

Summary: After a patient was administered a 5.75 GBq (155.2 mCi) dosage of iodine-131 (I-131) for ablation of residual thyroid tissue and for the treatment of metastatic thyroid cancer, it was learned that she was pregnant. The patient terminated the pregnancy.

Details: It is reported that preceding the administration of the I-131 therapy dosage, the licensee's nuclear medicine technologist and the authorized user, following internal policies and procedures to determine the pregnancy status of a patient, repeatedly questioned the patient about the possibility of a pregnancy and whether she was breast-feeding. The patient stated that she was not breast-feeding and there was no possibility of pregnancy. Approximately 3-1/2 hours after the I-131 administration, the licensee received the positive results of a pregnancy test previously ordered by the patient's referring physician. The licensee had not been aware that the referring physician had ordered the pregnancy test.

On notification of the pregnancy, the licensee told the patient she was pregnant and attempted to minimize the potential exposure to the fetus by having the patient increase fluid intake, to flush the free iodine from her system. The licensee also notified the patient's referring physician of the event. Ultrasound performed after identification of the pregnancy confirmed that the patient had been approximately 13-1/2 weeks pregnant with twins, at the time of the procedure.

Results: The licensee does not expect the patient to experience any ill effects. The dose equivalent to each fetus was estimated to be about 0.38 sievert (Sv) (38 rem) and the dose equivalent to each fetal thyroid was estimated to be more than 2000 Sv (200,000 rem). The licensee expected that such a dose would result in the following likely effects to the fetuses: (1) thyroid ablation; (2) a 30% increase in the likelihood of microcephaly; (3) a 20%-50% increase in the probability of childhood cancer; and (4) an increased probability for mental retardation. Based on this information, the patient elected to terminate the pregnancy.

What preventive action(s) could stop reoccurrence of a similar event? Consider both corrective (immediate and long term) and preventive actions.

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