Context: Serum thyroglobulin (Tg) is a highly sensitive and specific tumor marker, employed in post-operative management of patients with differentiated thyroid carcinomas. Tumor shrinkage of radioiodine-refractory thyroid cancer (RAIR-DTC) treated with multitarget kinase inhibitors as lenvatinib, expressed according to the Response Evaluation Criteria in Solid Tumors (RECIST), is also associated with a drastic reduction of Tg levels. However, interference caused by circulating thyroglobulin autoantibodies (TgAb) represents the main limitation in the clinical use of Tg.
Objective: To evaluate if in RAIR-DTC TgAb could be considered a surrogate marker of Tg in monitoring response to treatment with lenvatinib.
Design: We retrospectively evaluated patients who had started lenvatinib and correlated serum Tg and TgAb with the radiological response across visits.
Setting: University of Pisa, Italy.
Patients: We selected 9/97 RAIR-DTC patients with detectable TgAb.
Intervention: None.
Main outcome measures: None.
Results: Tg values correlated neither with TgAb title nor with radiological response across visits. Greater decreases in TgAb titer correlated with favorable radiological response to lenvatinib after 1 month (Spearman's correlation = 0.74, P = .021) and 6 months (correlation = 0.61, P = .079). According to RECIST, patients with partial response showed a ∼10-fold greater decrease in TgAb compared to those with stable disease at 1 month (median TgAb decrease: -142 vs -14 IU/mL, P = .01) and those with progressive disease at 6 months (median TgAb decrease: -264 vs-24 IU/mL, P = .04).
Conclusion: TgAb evaluation may represent a reliable surrogate marker for Tg trend in evaluating response of RAIR-DTC to treatment with lenvatinib. A multicentric study would be useful to confirm our results.
Keywords: differentiated thyroid carcinoma; lenvatinib; radioiodine-refractory differentiated thyroid cancer; thyroglobulin autoantibodies.
Published by Oxford University Press on behalf of the Endocrine Society 2023.