Pregnancy outcome after diagnosis of differentiated thyroid carcinoma: no deleterious effect after radioactive iodine treatment

Abstract

Purpose: Thyroid carcinoma is the second most common malignancy in young women, after breast cancer, aged 15-34 years in Hong Kong. Radioiodine or (131)I (RAI) has been confirmed as a useful treatment in the management of differentiated thyroid carcinoma (DTC). Serious concerns have been raised of the potential risks on subsequent pregnancies.

Methods and materials: We conducted a single-institute, retrospective analysis of the gestational history of 104 patients who became pregnant after the diagnosis of DTC. The patients were interviewed for pregnancy outcome, and the data were supplemented by a review of the medical records in the Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong.

Results: Of 263 pregnancies observed, the prior RAI administration in 153 (scanning dose or ablative dose) did not adversely affect the pregnancy outcome as determined by the rate of successful delivery, mode of delivery, live birth demographics (e.g., birth weight, gender distribution). In all live births, neither congenital malformations nor first year neonatal mortality was observed. Of 116 pregnancies in 68 patients who received an ablative dose (mean, 96.6 mCi) of RAI, 78 live births were reported. The updated information on these children at age 1 month to 30.8 years (mean, 7.9 years; SD 7.3) showed that they had no abnormal development. The incidence of miscarriages was not different in those with prior RAI administration. However, the incidence of preterm delivery was greater in those with a history of RAI (p = 0.03). A higher ablative dose (>80 mCi) and shorter interval between RAI and conception (<1 year) did not significantly alter the pregnancy outcome. Two patients were inadvertently given an RAI scanning dose during pregnancy. One decided to continue the pregnancy; a healthy 6-year-old boy was reported at the last update. Fifteen patients had DTC diagnosed during pregnancy; 2 terminated the pregnancy and 13 decided to continue their pregnancy. All children were born in good health. For DTC diagnosed during the first trimester of pregnancy, the deferral of thyroid surgery to the second trimester is a good compromise for earlier treatment of the malignancy while continuing the pregnancy.

Conclusion: Radioiodine in young women with DTC did not have deleterious effects on subsequent pregnancies. Proper education and instruction for avoiding conception within 1 year after RAI is a prudent recommendation, allowing for RAI clearance and hormonal stabilization.