Long-Term Effects of Radioiodine Treatment on Female Fertility in Survivors of Childhood Differentiated Thyroid Carcinoma.

Background. Differentiated thyroid cancer (DTC) during childhood is a rare disease. Its excellent survival rate requires a focus on possible long-term adverse effects. This study aimed to evaluate fertility in female survivors of childhood DTC by assessing various reproductive characteristics combined with anti-Müllerian hormone (AMH) levels (a marker of ovarian reserve). Methods. Female survivors of childhood DTC, diagnosed at ≤18 years of age between 1970 and 2013 were included. Survivors were excluded when follow-up time was less than 5 years or if they developed other malignancies before or after diagnosis of DTC. Survivors filled out a questionnaire regarding reproductive characteristics (e.g. age at menarche and menopause, pregnancies, pregnancy outcomes, need for assisted reproductive therapy). Survivors aged <18 years during evaluation received an altered questionnaire without questions regarding pregnancy and pregnancy outcomes. These data were combined with information from medical records. AMH levels were measured in serum samples and were compared with AMH levels from 420 women not treated for cancer. Results. Fifty-six survivors with a median age of 31.0 years (interquartile range [IQR] 25.1-39.6 years) were evaluated after a median follow-up of 15.4 years (IQR 8.3-24.7 years). The median cumulative dose of radioactive iodine (131-I) administered was 7.4 GBq (IQR 3.7-13.0 GBq/200.0 mCi, IQR 100.0-350.0 mCi). Twenty-five out of 55 survivors aged 18 years or older during evaluation reported 64 pregnancies, 45 of which resulted in live birth. Of these 55, 10.9% visited a fertility clinic. None of the survivors reported premature menopause. Age at AMH evaluation did not differ between DTC survivors and the comparison group (P = 0.268). Median AMH levels did not differ between DTC survivors and the comparison group (2.0 μg/L [IQR 1.0-3.7 μg/L] vs.1.6 μg/L [IQR 0.6-3.1 μg/L], respectively, P = 0.244). The cumulative dose of 131-I was not associated with AMH levels in DTC survivors (rs = 0.210, P = 0.130). Conclusions. Female survivors of DTC who received 131-I treatment during childhood do not appear to have major abnormalities in reproductive characteristics nor in predictors of ovarian failure.