Delay of initial radioactive iodine therapy beyond 3 months has no effect on clinical responses and overall survival in patients with thyroid carcinoma: A cohort study and a meta-analysis

Background More than a third of thyroid carcinoma (TC) patients require treatment with radioactive iodine (RAI), but the timing of initial RAI therapy after thyroidectomy remains controversial. Methods We included 1224 differentiated thyroid carcinoma (DTC) patients during 2015-2019, divided them into the early (<= 3 months) and the delayed (>3 months) groups based on the interval between surgery and the initial RAI. Clinical outcomes were assessed within 6-8 months of treatment with RAI, including excellent response (ER), indeterminate response (IDR), biochemical incomplete (BIR) and structural incomplete response (SIR). Further transformed them into dichotomous outcomes, we therefore introduced the ordered/binary logistic regression to assess the relation of time interval and quaternary/dichotomous outcomes, respectively. Finally, we conducted a meta-analysis for cohort study to investigate the effect of timing of RAI therapy on the prognosis of TC. Results Delay RAI therapy beyond 3 months reduced the IR (BIR + SIR) rate in the present cohort study (RR = 0.67, 95% CI: 0.49-91). Following meta-analysis including 38,688 DTC patients confirmed these results (RR = 0.77, 95% CI: 0.66-0.91), further revealed the duration of treatment does not influence OS (pooled RR = 1.05, 95% CI: 0.83-1.33). Conclusion Delayed initial RAI therapy beyond 3 months but no later than 6 months did not impair the prognosis of TC.