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Original Investigation
October 21, 2019

Association Between Pregnancy Outcomes and Radioactive Iodine Treatment After Thyroidectomy Among Women With Thyroid Cancer

Author Affiliations
  • 1Health Insurance Review and Assessment Service, Seoul, South Korea
  • 2Department of Nuclear Medicine, College of Medicine, Ewha Womans University, Seoul, South Korea
  • 3Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea
JAMA Intern Med. 2020;180(1):54-61. doi:10.1001/jamainternmed.2019.4644
Key Points

Question  What is the appropriate interval between treatment and pregnancy among women who receive radioactive iodine treatment after thyroidectomy for thyroid cancer?

Findings  In this population-based cohort study of 111 459 South Korean women of childbearing age (20-49 years) who underwent thyroidectomy for differentiated thyroid carcinoma, the receipt of radioactive iodine treatment after surgery was not associated with an increase in the rates of abortion, preterm delivery, or congenital malformation when conception occurred 6 months or more after treatment compared with surgery alone.

Meaning  These large-scale real-world data suggest that radioactive iodine treatment after thyroidectomy is not associated with an increase in adverse pregnancy outcomes when conception occurs after a 6-month waiting period.

Abstract

Importance  Current guidelines recommend that women delay pregnancy for 6 to 12 months after the receipt of radioactive iodine treatment (RAIT) following thyroidectomy for differentiated thyroid carcinoma. Although concerns exist regarding the risks associated with pregnancy after RAIT, no large-scale study, to date, has investigated the association between RAIT and pregnancy outcomes.

Objective  To investigate whether RAIT was associated with increases in adverse pregnancy outcomes among South Korean women who received RAIT after thyroidectomy for thyroid cancer and to evaluate the appropriate interval between RAIT and conception.

Design, Setting, and Participants  This population-based cohort study used the Health Insurance Review and Assessment database of South Korea to identify a total of 111 459 women of childbearing age (20-49 years) who underwent thyroidectomy for the treatment of differentiated thyroid carcinoma between January 1, 2008, and December 31, 2015. Participants were allocated to 2 cohorts: those who underwent surgery alone (n = 59 483 [53.4%]) and those who underwent surgery followed by RAIT (n = 51 976 [46.6%]). The pregnancy outcomes data were collected from January 1, 2008, to December 31, 2017.

Main Outcomes and Measures  The rates of abortion (both spontaneous and induced), preterm delivery, and congenital malformation were assessed. Multivariate logistic regression models were used to control for confounding variables.

Results  Among the 111 459 women of childbearing age who underwent thyroidectomy with or without RAIT for the treatment of thyroid cancer, the mean (SD) age at surgery or RAIT was 39.8 (6.7) years. Of those, 10 842 women (9.7%) became pregnant, and the mean (SD) age at conception was 33.3 (4.4) years. The rates of abortion, preterm delivery, and congenital malformation among patients who underwent surgery alone compared with patients who underwent surgery followed by RAIT were 30.7% vs 32.1% for abortion, 12.8% vs 12.9% for preterm delivery, and 8.9% vs 9.0% for congenital malformation, respectively (P > .05). A subgroup analysis based on the interval between RAIT and conception indicated congenital malformation rates of 13.3% for the interval of 0 to 5 months, 7.9% for 6 to 11 months, 8.3% for 12 to 23 months, and 9.6% for 24 months or more. The adjusted odds ratio of congenital malformation was 1.74 (95% CI, 1.01-2.97; P = .04) in conceptions that occurred 0 to 5 months after RAIT compared with conceptions that occurred 12 to 23 months after RAIT. The abortion rates based on the interval between RAIT and conception were 60.6% for the interval of 0 to 5 months, 30.1% for 6 to 11 months, 27.4% for 12 to 23 months, and 31.9% for 24 months or more.

Conclusions and Relevance  These large-scale real-world data indicate that receipt of RAIT before pregnancy does not appear to be associated with increases in adverse pregnancy outcomes when conception occurs 6 months or more after treatment.

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