Post-Surgical Ablative or Adjuvant Radioiodine Therapy Has No Impact on Outcome in 1-4 cm Differentiated Thyroid Cancers without Extrathyroidal Extension.

Simone De Leo,Laura Fugazzola,Luca Persani,Leonardo Vicentini,Sonia Palazzo,Giacomo Gazzano,Matteo Trevisan,Carla Colombo

doi:10.3390/jcm10194452

Abstract

Whether to conduct remnant ablation or adjuvant radioactive iodine (RAI) therapy in patients with intrathyroidal differentiated thyroid carcinoma (DTC), sized 1.1–4 cm, is debated. We evaluated the impact of RAI on outcome in this category of DTCs. We retrospectively enrolled 308 patients submitted to total thyroidectomy: 198 had tumors sized 1.1–2 cm (Group 1) and 110 of 2.1–4 cm (Group 2). Both groups were divided into patients receiving and not receiving RAI after surgery. RAI+ and RAI− patients did not significantly differ, regarding several clinical and pathological features. Final outcome was defined according to dynamic risk stratification. Remission was observed in the majority of Group 1 and Group 2 patients and outcome did not significantly differ between RAI+ and RAI− patients: respectively, 95.8% vs. 93.7% in Group 1, and 87.7% vs. 86.5% in Group 2. The majority of persistent cases, either RAI+ or RAI−, received therapeutic RAI administration, and about 50% of RAI− cases had an excellent response at final follow up, whereas no RAI+ persistent patients had a beneficial effect. Our findings demonstrate that patients with an intrathyroidal DTC sized 1.1–4 cm do not benefit from RAI. The outcome of these patients remains favorable, and the few patients with persistent diseases can be treated with RAI during follow up.

Highlights

Differentiated thyroid cancer (DTC) accounts for more than 90% of thyroid tumors and its incidence has progressively increased in the last few decades [1]
Attention is mainly focused on the risk of recurrence, reliably predicted by the American Thyroid Association (ATA) risk classification [2]
ATA guidelines state that DTC between 1 and 4 cm should not routinely be treated by radioactive iodine (RAI) [2], while the Nuclear Medicine Societies recommend RAI ablation for all tumors larger than 1 cm [6,7], based on the impossibility to reliably discriminate between patients who could benefit or not from this treatment [8]

Summary

Introduction

Differentiated thyroid cancer (DTC) accounts for more than 90% of thyroid tumors and its incidence has progressively increased in the last few decades [1]. Remnant ablation has a particular role in determining initial staging and facilitating follow up, while adjuvant treatment improves disease-specific and progression-free survival, decreases recurrences, and has a curative intent, even though in many patients, surgery may be sufficient [4]. While both European and American Thyroid and Nuclear Medicine Societies agree not to perform RAI ablation in microcarcinomas (≤1 cm) [2,5,6,7], there is still controversy regarding low-risk thyroid tumors >1 cm. The aim of our study was to evaluate (i.e., without minimal or gross extrathyroidal extension and without local and/or distant metastases) the impact on outcome of radioiodine used for ablative or adjuvant purposes in patients with intrathyroidal DTCs sized 1.1–4 cm

Objectives

Methods

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Discussion

Conclusion