Pregnancy and Progression of Differentiated Thyroid Cancer: A Propensity Score-Matched Retrospective Cohort Study.

[CONTEXT AND OBJECTIVE] Differentiated thyroid cancer (DTC) is very common in women of reproductive age. However, it remains unclear whether pregnancy is associated with DTC progression before surgical treatment.

[METHODS] This retrospective cohort study, conducted at the Peking University Third Hospital in Beijing, China between January 2012 and December 2022, included 311 eligible women aged 20 to 45 years. To control for potential confounders, we first used propensity score matching (PSM) to match the pregnant group (n = 48) with the nonpregnant group (n = 154) on age, tumor size, tumor type, and Hashimoto's thyroiditis status at baseline, and then used Cox proportional risk models stratified by the matched pairs to estimate the association of pregnancy with DTC progression.

[RESULTS] After PSM, the pregnant and nonpregnant groups were well comparable at baseline (standardized difference < 10% and P > .05). Over an average observation period of 2.5 years, we observed no difference between the pregnant group and the matched nonpregnant group in DTC progression-free survival (hazard ratio [HR] = 0.96; 95% CI, 0.56 to 1.65; P = .895), tumor enlargement-free survival (HR = 0.99; 95% CI, 0.56 to 1.76; P = .969) or lymph node metastasis-free survival (LNM) (HR = 0.67; 95% CI, 0.21 to 2.13; P = .498). The postoperative pathological characteristics also showed no significant difference between the pregnant and nonpregnant groups (P > .05).

[CONCLUSION] Pregnancy seemed to be irrelevant to DTC progression-free survival before surgical treatment. Further prospective cohort studies are needed to translate this finding into clinical practice.