PSAT243 Late Versus Early Administration of Radioiodine Therapy for Patients with Differentiated Thyroid Cancer: A Systematic Review and Meta-analysis

Abstract Background Radioiodine (RAI) therapy is an important adjuvant therapy for differentiated thyroid carcinoma (DTC) patients. Several studies have demonstrated the efficacy of RAI in reducing the risk of thyroid cancer recurrence and mortality; however, the ideal timing to initiate RAI after surgery is debatable. This systematic review and meta-analysis evaluates the risk of achieving excellent response and mortality when comparing late administration versus early administration of RAI in patients with DTC. Methods We searched Medline, Embase, Scopus, and Cochrane Database from inception to April 2021 to identify experimental and observational studies that evaluated the impact of different timings of RAI after surgery (3 months, 6 months, 9 months) on the risk of excellent response and thyroid-specific mortality in DTC patients with low, intermediate, and high risk of recurrence. We used random-effects model to pool dichotomous variables with odd ratios (OR) and their confidence intervals (95%CI). The risk of bias was evaluated using the Newcastle Ottawa Scale. PROSPERO Protocol ID CRD42021267036. Results We included 12 retrospective cohort studies with 34,833 patients. The majority of participants were female (78.00%) and the mean age ranged from 39.70 (± 3.40) to 51.60 (± 1.70) years. In patients with low-to-intermediate risk of recurrence, there were no differences in excellent response (OR 0.76, 95%CI: 0.34-1.68, I2: 78.00%, n=1099) and mortality risk (OR 1.00, 95%CI: 0.84-1.19, I2: 0.00%, n=21450) in the late group (>3 months) compared to the early group (3 months) when compared to the early group (6 months) when compared to the early group (