Clinical course and outcome of differentiated thyroid cancer patients with pregnancy after diagnosis of distant metastasis

Purpose There is no sufficient data about the clinical course and outcome in thyroid cancer patients who become pregnant after diagnosis of distant metastasis (DM). The current study was conducted to collect information regarding the clinical and reproductive characteristics, and outcomes in thyroid cancer patients who became pregnant after being diagnosed with DM. Methods Records of 125 differentiated thyroid cancer (DTC) patients with age ≤45 years at DM diagnosis who had visited Ito Hospital from January 2005 to June 2021 were retrospectively reviewed. Among those 125 patients, 28 who became pregnant after DM diagnosis were classified as pregnancy group, and the remained 97 patients were classified as comparator group. Results In pregnancy group, the median age at malignancy diagnosis, DM diagnosis, and first pregnancy after DM diagnosis was 25 years (range, 4–41 years), 27 years (range, 11–41 years), and 32 years (range, 25–45 years), respectively. Fifty-five pregnancies and 40 live births were reported. Other pregnancy outcomes were miscarriage ( n = 14) and induced abortion ( n = 1). The 10-year progression-free survival (PFS) rates of pregnant and comparator group were 92.1% and 74.4%, respectively ( p = 0.018). The multivariate analysis showed that multiple 131 I treatment was independent negative prognostic factor for PFS ( p = 0.046). Conclusions DTC patients with age ≤45 years at DM diagnosis had good survival even though they became pregnant. Our results add to the information required for counseling thyroid cancer patients who have concerns about their fertility in the future.