Microscopic extrathyroid extension in papillary thyroid carcinoma: impact on response to therapy.

Bernardo Marques,Raquel G Martins,Fernando Rodrigues,Jacinta Santos,Joana Couto,Teresa Martins

doi:10.20945/2359-3997000000210

Abstract

Objectives Evaluate the impact of microscopic extrathyroid extension (MEE) on outcome and therapy response in patients with cT1 and cT2 papillary thyroid carcinoma (PTC). Subjects and methods Retrospective study of 970 consecutive patients, who underwent surgery for PTC between 2000 and 2016. All patients had: tumours ≤ 4 cm, apparent complete tumour resection, without clinically apparent lymph node or distant metastasis at diagnosis and nonaggressive histologic variant. Results Based on the finding of MEE, 175 (18.0%) patients were upstaged to T3. They were older (53.9 versus 50.6 years; P = 0.004) and were more prone to have multifocal tumours (38.2% versus 24.8%; P = 0.001). Radioiodine ablation therapy (RAI) was administered more often to MEE patients (92% versus 40.5%; P < 0.001), as well as prophylactic lymph node resection (35.4% versus 28.6%, P = 0.048). They were more likely to have biochemical incomplete response (4% versus 0.3%; P = 0.03) at the end of the follow-up period. There was no significant association between MEE and recurrence rate, persistence of disease or disease-specific mortality. Conclusion These results support the changes made to the latest edition of the TNM staging system, regarding MEE. Although incomplete biochemical response is more common in these patients, it does not seem to affect their prognosis.

Highlights

Well-differentiated thyroid cancer (WDTC) is, generally, a disease with good prognosis
This study aims to evaluate the impact of microscopic extrathyroid extension (MEE) on outcome in patients with otherwise T1 and T2 papillary thyroid carcinoma (PTC) and its effect on therapy response
The current study describes the outcomes of a very large cohort of patients with cT1/T2N0 PTC, with a long follow-up period

Summary

Introduction

Well-differentiated thyroid cancer (WDTC) is, generally, a disease with good prognosis. Its management continues to move towards a more personalized approach and initial risk stratification is an important tool used to guide early initial therapy and follow-up, such as extent of thyroid surgery, RAI and levothyroxine therapy [1,2,3,4]. These initial risk estimates are further modified based on each patient’s response to therapy and the biological behaviour of the disease – an approach called dynamic risk stratification. There is no data supporting the finding of MEE as a risk factor for disease recurrence or mortality and recent studies suggest that MEE may have little importance in tumours smaller than 4cm

Objectives

Results

Conclusion