Pregnancy and the prognosis of patients previously treated for differentiated thyroid cancer: a systematic review and meta-analysis

IMPORTANCEDifferentiated thyroid cancer (DTC) is commonly diagnosed in women of child-bearing age, but whether pregnancy influences the prognosis of DTC remained controversial. OBJECTIVEThis systematic review and meta-analysis aimed to summarize and appraise the existing evidence of the impact of pregnancy on the prognosis of patients previously treated for DTC. DATA SOURCESWe searched PubMed, Embase, Web of Science, Cochrane, and Scopus until February 2023. STUDY SELECTIONStudies of patients diagnosed and treated for DTC before pregnancy reporting the recurrence/progression condition of DTC were included. Case reports and studies failing to identify the time of diagnosis or initial treatment were excluded. DATA EXTRACTION AND SYNTHESISMeta-analyses were conducted according to MOOSE guideline. Data extraction was conducted by two independent investigators with a standard form. Pooled effect estimates were calculated in a random-effects model. MAIN OUTCOMES AND MEASURESDTC recurrence/progression and the type of recurrence/progression (structural or biochemical). RESULTSAmong the 10 included studies (n = 625), 4 (n = 143) of them compared the pregnancy group with the non-pregnancy group while the remaining 6 (n = 482) only included the pregnant patients. The pooled proportion of recurrence/progression in all pregnant patients was 13% (95% CI, 6%, 25%). Compared with the non-pregnancy group, the pooled odds ratio of recurrence/progression in the pregnancy group was 0.75 (95% CI, 0.45, 1.23). Two included studies focused on patients with distant metastasis and also did not observe difference in disease recurrence/progression between the pregnancy group and the non-pregnancy group [OR, 0.51 (95% CI, 0.14-1.87)]. Six included studies also reported response to therapy status prior to pregnancy, and the pooled proportion for recurrence/progression in pregnant DTC patients with excellent response (n=287), indeterminate response (n=44), biochemical incomplete response (n=41) and structural incomplete response (n=70) was 0.00 (95% CI, 0.00-0.86), 0.09 (95% CI, 0.00-0.99), 0.20 (95% CI, 0.06-0.46) and 0.45 (95% CI, 0.17-0.76), respectively. There was a trend for an increasingly higher risk of recurrence/progression from excellent, indeterminate, biochemical incomplete to structural incomplete response to therapy (P<0.05). CONCLUSIONS AND RELEVANCEPregnancy appears to have a minimal impact on the prognosis of DTC with initial treatment. Clinicians may pay more attention to the progression of DTC among pregnant women with biochemical and/or structural persistence. Key PointsO_ST_ABSQuestionC_ST_ABSDoes subsequent pregnancy has an impact on the prognosis of patients previously treated for differentiated thyroid cancer (DTC)? FindingsIn this systematic review and meta-analysis of 10 studies including 625 patients previously treated for DTC and underwent pregnancy subsequently, pregnancy might have a minimal impact on DTC recurrence/progression. Patients with biochemical and/or structural incomplete response to DTC treatment prior to pregnancy appears to have a higher risk of DTC recurrence/progression compared to those with excellent or indeterminate response. MeaningThough pregnancy appears to have little influence on the prognosis of patients previously treated for DTC, patients with biochemical and/or structural persistence should be more carefully monitored during pregnancy.