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.

The Association of Pregnancy with Disease Progression in Patients Previously Treated for Differentiated Thyroid Cancer: A Propensity Score-Matched Retrospective Cohort Study.

Background: Differentiated thyroid cancer (DTC) is increasingly common in women of reproductive age. However, whether pregnancy increases the risk of DTC progression/recurrence after treatment remains controversial. The study aimed to assess the association of pregnancy with risk of progression in patients previously treated for DTC. Methods: This was a retrospective cohort study following 123 pregnant women and 1376 nonpregnant women at Peking University Third Hospital after initial treatment for DTC between January 2012 and December 2022. To control the effect of confounding, we carefully matched pregnancy (n = 107) and nonpregnancy groups (n = 298) in terms of baseline characteristics by using propensity score matching (PSM). Results: At baseline, the pregnancy and nonpregnancy groups were balanced in all matched variables. At follow-up, the percentage of DTC progression in the two groups was 12 (11.8%) and 47 (15.8%), respectively. Regression models showed no evidence of association of pregnancy with the risk of progression (odds ratio: 0.74 and 95% confidence interval: 0.37-1.50; p = 0.404), and remained consistent across long/short follow-up and other subgroup variables. We found that the shorter the time interval between treatment and pregnancy, the higher the risk of DTC progression (ptrend = 0.019). Conclusions: The risk of DTC progression in pregnant women was not higher than that in the well-matched, nonpregnant women. For young women previously treated for DTC, disease progression might not be a concern for their future pregnancy plan, but it seems safer to wait at least 1 year before pregnancy compared with immediate pregnancy.