Impact of pregnancy on outcome and prognosis of survivors of papillary thyroid cancer.

Background: Papillary thyroid cancer (PTC) commonly affects women of child-bearing age. During normal pregnancy, several factors may have a stimulatory effect on normal and nodular thyroid growth. The aim of the study was to determine whether pregnancy in thyroid-cancer survivors poses a risk of progression or recurrence of the disease.

Methods: The files of 63 consecutive women who were followed at the Endocrine Institute for PTC in 1992-2009 and had given birth at least once after receiving treatment were reviewed for clinical, biochemical, and imaging data. Thyroglobulin levels and neck ultrasound findings were compared before and after pregnancy. Demographic and disease-related characteristics and levels of thyroid-stimulating hormone (TSH) during pregnancy were correlated with disease persistence before conception and disease progression during pregnancy using Pearson's analysis.

Results: Mean time to the first delivery after completion of thyroid-cancer treatment was 5.08 ± 4.39 years; mean duration of follow up after the first delivery was 4.84 ± 3.80 years. Twenty-three women had more than one pregnancy, for a total of 90 births. Six women had evidence of thyroid cancer progression during the first pregnancy; one of them also showed disease progression during a second pregnancy. Another two patients had evidence of disease progression only during their second pregnancy. Mean TSH level during pregnancy was 2.65 ± 4.14 mIU/L. There was no correlation of disease progression during pregnancy with pathological staging, interval from diagnosis to pregnancy, TSH level during pregnancy, or thyroglobulin level before conception. There was a positive correlation of cancer progression with persistence of thyroid cancer before pregnancy and before total I-131 dose was administered.

Conclusions: Pregnancy does not cause thyroid cancer recurrence in PTC survivors who have no structural or biochemical evidence of disease persistence at the time of conception. However, in the presence of such evidence, disease progression may occur during pregnancy, yet not necessarily as a consequence of pregnancy. The finding that a nonsuppressed TSH level during pregnancy does not stimulate disease progression suggests that it may be an acceptable therapeutic goal in this setting.