Impact of pregnancy on prognosis of differentiated thyroid cancer: clinical and molecular features

Differentiated thyroid cancer (DTC) commonly occurs in women of child-bearing age and represents the second most frequent tumor diagnosed during pregnancy only behind breast cancer. It is possible that associated physiological changes could favor tumor development and growth. However, few data are available about the outcome of DTC related to pregnancy, leading to conflicting results.

Among the study population, 340 patients with DTC <45 years old were retrospectively studied. Patients were divided into three groups according to the time of tumor diagnosis in respect of pregnancy. Group 1, diagnosis of DTC at least 2 years after delivery; group 2, diagnosis during pregnancy or within the second year after delivery; and group 3, nulliparous patients at the time of diagnosis. We evaluated clinical outcome and immunohistochemical expression of estrogen receptor α (ERα), ERβ, progesterone receptor, and aromatase. We also analyzed the gene expression of NIS (SLC5A5) and the prevalence of BRAF(V600E) mutations.

Persistence/recurrence of disease was significantly higher in group 2 patients than control groups (P=0.023). No significant differences were observed in other clinical parameters. Furthermore, no differences among the groups were recorded about ER pattern, NIS expression, and BRAF mutations.

Persistence/recurrence of DTC is significantly higher in pregnant patients, suggesting that pregnancy could really exert a negative prognostic role in patients with DTC. The underlying mechanisms are not yet clarified and further studies are required. Our results suggest that a more careful follow-up is needed when diagnosis of DTC occurs during pregnancy or shortly after.