Efficacy of Empirical Radioiodine Therapy in Patients with Differentiated Thyroid Cancer and Elevated Serum Thyroglobulin without Evidence of Structural Disease: A Propensity Score Analysis

SIMPLE SUMMARY: In patients with differentiated thyroid cancer, the standard treatment consists in surgery followed by radioactive iodine (RAI) therapy. Follow-up is usually performed by serum thyroglobulin measurements and neck ultrasound, in order to detect the presence of persistent disease. Detectable thyroglobulin levels after the first treatment may indicate the presence of still viable tumor cells. Therefore, empiric radioiodine administration can be considered for both diagnostic and therapeutic purposes in the presence of elevated thyroglobulin after the first treatment also in patients without evidence of persistent disease. A beneficial effect of this approach has been suggested, in particular in patients with high suspicious of distant metastases at post-therapy whole body scan. However, a significant impact on patient outcomes has not been addressed andthe identification of patients who may benefit from this approach has not been fully clarified. Therefore, the use of empiric RAI therapy in patients with DTC and its potential impact on outcome still remains controversial. ABSTRACT: We assessed the outcome of administration of empiric radioactive iodine (RAI) therapy to patients with differentiated thyroid cancer (DTC), in a propensity-score-matched cohort of patients with biochemical incomplete response (BIR) and without evidence of structural disease. We retrospectively evaluated 820 DTC patients without distant metastases, who underwent total thyroidectomy followed by RAI therapy, with available BIR at 12 months and follow-up evaluations. The patients were categorized according to the administration of empiric therapy (ET). To account for differences between patients with (n = 119) and without (n = 701) ET, a propensity-score-matched cohort of 119 ET and 119 no-ET patients was created. The need for additional therapy and the occurrence of structural disease were considered as end-points. During a median follow-up of 53 months (range 3–285), 57 events occurred (24% cumulative event rate). The rate of events was significantly higher in the no-ET compared to the ET patients (30% vs. 18% p < 0.001). The multivariate Cox analysis identified age (p < 0.01), pre-therapy Tg (p < 0.05) and empiric RAI therapy (p < 0.01) as predictors of outcome. The Kaplan–Meier analysis found that progression-free survival was lower in no-ET patients compared to the ET group (p < 0.01). In patients with DTC treated with surgery and RAI, and with biochemical incomplete response at the 12-month evaluation, their prognosis seemed to be affected by Tg values and the empiric treatment. The identification of candidates for this approach may improve prognosis.