Response to Therapy Status Is an Excellent Predictor of Pregnancy-Associated Structural Disease Progression in Patients Previously Treated for Differentiated Thyroid Cancer.

Background: Pregnancy may be associated with an increased risk of recurrence/progression of differentiated thyroid cancer (DTC). However, it is unclear if the impact of pregnancy would differ based on pre-pregnancy response to therapy status. The objective of this study was to investigate the risk of recurrence/progression of DTC, applying the response to therapy assessments to pre-pregnancy status as recommended by the 2015 American Thyroid Association thyroid cancer guidelines. Methods: This was a retrospective review of 235 women followed at Memorial Sloan Kettering Cancer Center for DTC who had a term pregnancy after initial treatment for DTC between 1997 and 2015. Results: Structural disease recurrence/progression after pregnancy was documented in 5% (11/235) of the patients. When evaluated 3-12 months after delivery, patients who had an excellent, indeterminate, or biochemical incomplete response before pregnancy continued to show no evidence of structurally identifiable disease. Conversely, in women with a structural incomplete response to therapy prior to pregnancy, structural progression (defined as ≥3 mm increase in the size of known disease or identification of new metastatic foci) was identified after delivery in 29% (11/38). However, additional therapy was recommended during the first postpartum years in only 8% (3/38) of those patients who had a structural incomplete response to therapy prior to pregnancy, while the remainder (92%) continued to be followed with observation. Conclusion: None of the patients with an excellent, indeterminate, or biochemical incomplete response to therapy prior to pregnancy developed structurally identifiable disease after a full-term delivery. Even though structural disease progression was seen in almost a third of the patients with known structural disease prior to pregnancy, only a minority of these patients had changes sufficient to warrant additional therapy. These data confirm that pre-pregnancy response to therapy status is an excellent predictor of pregnancy-associated disease progression in women previously treated for DTC. [ABSTRACT FROM AUTHOR]