Postoperative Radioiodine Treatment within 9\xa0Months from Diagnosis Significantly Reduces the Risk of Relapse in Low-Risk Differentiated Thyroid Carcinoma

Jolanta Krajewska,Aleksandra Kropinska,Michal Jarzab,Aleksandra Kukulska,Agnieszka Czarniecka,Jozef Roskosz,Aleksandra Krol,Ewa Paliczka-Cieslik,Zbigniew Puch,Barbara Jarzab,Zbigniew Wygoda,Daria Handkiewicz-Junak

doi:10.1007/s13139-019-00608-8

Abstract

PurposeAlthough postoperative radioiodine (RAI) therapy has been used in patients with differentiated thyroid carcinoma (DTC) for many years, there is still lack of data defining the timing of RAI administration. A retrospective analysis was carried out to answer the question whether the time of postoperative RAI treatment demonstrated any impact on long-term outcomes, particularly in low-risk DTC.MaterialThe analyzed group involved 701 DTC patients staged pT1b-T4N0-N1M0, who underwent total thyroidectomy and postoperative RAI therapy. According to the time interval between DTC diagnosis and RAI administration, patients were allocated to one of three groups: up to 9 months (N = 150), between 9 and 24 months (N = 323), and > 24 months (N = 228). Median follow-up was 12.1 years (1.5–15.2).ResultsBased on an initial DTC advancement and postoperative stimulated thyroglobulin concentration patients were stratified as a low-, intermediate-, and high-risk group. Low-risk patients, who received RAI therapy up to 9 months, demonstrated significantly lower risk of relapse comparing to those, in whom RAI was administered between 9 and 24 months and after 24 months since DTC diagnosis: 0%, 5.5%, and 7.1%, respectively. Regarding intermediate- and high-risk groups, the differences in the timing of postoperative RAI treatment were not significant.ConclusionIf postoperative RAI treatment is considered in low-risk DTC, any delay in RAI administration above 9 months since diagnosis may be related to poorer long-term outcomes.

Highlights

Differentiated thyroid carcinoma (DTC) is the most common endocrine malignancy, characterized by a very good prognosisNucl Med Mol Imaging (2019) 53:320–327 extrathyroidal extension, clinically apparent lymph node involvement or distant metastases are present
Only recently apart from still opened question concerning postoperative RAI therapy “whether and whom to treat” another clinical problem has been raised in few studies: “when to treat” [16,17,18,19]? there is lack of scientific data, which precisely define a timeframe between DTC diagnosis and postoperative RAI treatment
Further DTC monitoring was based on the evaluation of serum TSH, Tg with Tg recovery, or Tg antibodies during thyroxine administration and neck US every 6 months following postoperative RAI therapy

Summary

Introduction

Differentiated thyroid carcinoma (DTC) is the most common endocrine malignancy, characterized by a very good prognosisNucl Med Mol Imaging (2019) 53:320–327 extrathyroidal extension, clinically apparent lymph node involvement or distant metastases are present. In 2009, postoperative RAI treatment was recommended in all patients with known distant metastases, gross extrathyroidal extension regardless of tumor size, primary tumor size > 4 cm in the absence of other risk factors and for selected patients with 1–4 cm intrathyroidal tumor and lymph node metastases, high-risk features or in those who demonstrated intermediate- or highrisk recurrence or DTC-related death. Such treatment was definitely not recommended for patients with unifocal or multifocal cancer < 1 cm if no high-risk features were present [3]. If postoperative RAI therapy was not necessary in a low-risk group, any delay in RAI administration would not result in poorer outcomes in comparison to patients treated “on time”

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