UCLA

Background

Radioactive iodine (RAI) ablation is frequently performed after initial surgery for well-differentiated thyroid cancer (WDTC). We examined the frequency and timing of childbirth as well as nononcologic complications after RAI ablation for WDTC on a population level.

Methods

A retrospective cohort study of 25,333 patients (18,850 women) with WDTC was performed using the California Cancer Registry and California Office of Statewide Health Planning and Development database, 1999-2008. The primary outcomes were birthrate and median time to first live birth among women of childbearing age. Secondary outcomes were nononcologic diagnoses occurring outside the acute setting (>30 days) after ablation.

Results

RAI ablation did not affect birthrate among women in the full dataset. However, in subgroup analyses, birthrate among women age 35-39 was significantly decreased in those who received RAI versus those who did not (11.5 versus 16.3 births per 1000 woman-years, p<0.001). Median time to first live birth after diagnosis of WDTC was prolonged among women who received RAI compared to those who did not (34.5 versus 26.1 months; p<0.0001). When 5-year age groups were examined individually, delay to first live birth was observed in women age 20-39 (p<0.05). This remained significant after adjustment for tumor characteristics, socioeconomic status, and marital status. The only nononcologic, nonreproductive adverse effect associated with RAI ablation was an increased rate of nasolacrimal stenosis (RR 3.44, p<0.0001).

Conclusions

RAI ablation is associated with delayed childbearing in women across most of the reproductive lifespan, and with decreased birthrate in the late reproductive years. The underlying mechanism likely involves physician recommendation to delay pregnancy, as well as a potential impact of RAI on both reproductive choice and reproductive health. Further investigation is merited.