Pregnancy During Active Surveillance of Papillary Thyroid Microcarcinoma

Abstract Introduction: Most patients diagnosed with papillary thyroid microcarcinoma (microPTC) classified as low risk and therefore eligible for active surveillance (AS) are women. Although age is a predictor of tumor progression (more frequent among young people), young adults are “appropriate” candidates for AS. Consequently, a proportion of patients with low-risk microPTC eligible for AS are women of childbearing age and knowledge of the effect of pregnancy on tumor progression is therefore important. In the Japanese population, Ito et al. observed this progression in only 8% of pregnancies. None of the series on the outcomes of AS in western populations has so far reported the behavior of microPTC in women who became pregnant during AS. Methods: We have submitted patients with low-risk microPTC to AS. Our management has been not to interrupt AS, i.e., not to indicate surgery when the patient wishes to become pregnant. We report here the results of five patients who became pregnant during AS and their follow-up up to 6 months after delivery. Results: The patients were 26 to 36 years old (median 29 years) when they became pregnant. None of them had a history of radiation exposure, one had a family history of PTC, one had associated Hashimoto’s thyroiditis, and all of them had only one tumor focus and were considered “appropriate” (but not “ideal”) candidates for AS. In fact, when pregnancy was diagnosed, the patients continued to exhibit the criterion for AS according to our initial protocol (tumor ≤ 1.2 cm, no apparent lymph node metastases [LNM] or extrathyroidal extension [ETE] on ultrasonography [US]). All women were monitored by monthly measurement of TSH and levothyroxine (L-T4) was administered during pregnancy to maintain TSH between 0.1 and 1 mIU/L. US was performed when pregnancy was diagnosed (between 6 and 9 weeks of gestation), around 22 weeks, at the end of pregnancy, and 6 months after delivery. During the evaluations, none of the patients had apparent LNM or ETE on US. None of the patients exhibited tumor growth, defined as an increase in diameter ≥ 3 mm. Tumor growth ≥ 50% was observed in only one patient, with a small reduction after delivery. Conclusions: Our preliminary results suggest that pregnancy is not associated with a high risk of progression of low-risk microPTC and that the desire to get pregnant or pregnancy should not be an exclusion factor for AS. References: Effects of Pregnancy on Papillary Microcarcinomas of the Thyroid Re-Evaluated in the Entire Patient Series at Kuma Hospital. Ito Y, Miyauchi A, Kudo T et al. Thyroid 2016; 26:156-60 AND Active Surveillance in Adults with Low-Risk Papillary Thyroid Microcarcinomas: A Prospective Study. Rosario PW, Mourão GF, Calsolari MR. Horm Metab Res. 2019; 51:703-8.