Abstract
BACKGROUND: Differentiated thyroid cancer (DTC) is commonly diagnosed in women of child-bearing age, but whether pregnancy influences the prognosis of DTC remains controversial. This study aimed to summarize existing evidence regarding the association of pregnancy with recurrence risk in patients previously treated for DTC. METHODS: We searched PubMed, Embase, Web of Science, Cochrane, and Scopus based on the prespecified protocol registered at PROSPERO (CRD42022367896). After study selection, two researchers independently extracted data from the included studies. For quantitative data synthesis, we used random-effects meta-analysis models to pool the proportion of recurrence (for pregnant women only) and odds ratio (OR; comparing the risk of recurrence between the pregnancy group and the nonpregnancy group), respectively. Then we conducted subgroup analyses to explore whether risk of recurrence differed by response to therapy status or duration of follow-up time. We also assessed quality of the included studies. RESULTS: A total of ten studies were included. The sample size ranged from 8 to 235, with participants' age at pregnancy or delivery ranging from 28 to 35 years. The follow-up time varied from 0.1 to 36.0 years. The pooled proportion of recurrence in all pregnant patients was 0.13 (95% confidence intervals [CI]: 0.06-0.25; I2 : 0.58). Among six included studies reporting response to therapy status before pregnancy, we observed a trend for increasingly higher risk of recurrence from excellent, indeterminate, and biochemically incomplete to structurally incomplete response to therapy ( Ptrend <0.05). The pooled risk of recurrence in the pregnancy group showed no evidence of a significant difference from that in the nonpregnancy group (OR: 0.75; 95% CI: 0.45-1.23; I2 : 0). The difference in follow-up time (below/above five years) was not associated with either the proportion of recurrence in all pregnant patients ( P >0.05) or the OR of recurrence in studies with a comparison group ( P >0.05). Two included studies that focused on patients with distant metastasis also did not show a significant difference in disease recurrence between pregnancy and nonpregnancy groups (OR: 0.51 [95% CI: 0.14-1.87; I2 : 59%]). CONCLUSION: In general, pregnancy appears to have a minimal association with the disease recurrence of DTC with initial treatment. Clinicians should pay more attention to progression of DTC among pregnant women with biochemical and/or structural persistence. REGISTRATION: PROSPERO, https://www.crd.york.ac.uk/PROSPERO/ ; No. CRD42022367896.