More Than 50% of Unifocal cN0 T1b/Small T2 Papillary Thyroid Carcinoma May Require Completion Thyroidectomy if Nodal Status is Evaluated

Overview

In absence of nodal metastases or aggressive features, thyroid lobectomy (TL) should be preferred over total thyroidectomy (TT) for small unifocal papillary thyroid carcinoma (PTC). However, occult, despite non-microscopic (\>2 mm), nodal metastases may be present in clinically node-negative (cN0) PTCs. Among 4216 thyroidectomies for malignancy (2014-2023), 110 (2.6%) TL plus ipsilateral central neck dissection (I-CND) were scheduled for unifocal cT1b/small cT2 (\<3 cm) cN0 PTCs. Nodes frozen section examination (FSE) was performed: when positive, completion thyroidectomy (CT) was accomplished during the same procedure. In presence of aggressive pathologic features, CT was suggested within 6 months from index operation.

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. Although its incidence has increased in recent decades, the prognosis is excellent due to the indolent nature of the disease. Despite that, recurrence rate of PTC remains common. Nowadays, the correct extent of thyroidectomy remains controversial. However, several studies demonstrated no significant differences in terms of disease-free survival (DFS) and loco-regional recurrence (LRR) in differentiated thyroid carcinoma (DTC) \> 1cm after thyroid lobectomy (TL) vs total thyroidectomy (TT). In absence of preoperative high-risk features (HRFs), the most recent NCCN and ATA guidelines consider unifocal 1-4 cm PTCs eligible for TL. However, many of HRFs are highlighted only after pathological examination: positive nodal status, aggressive tumor subtype, multifocality, microscopic extrathyroidal extension (ETE), positive margin and lymphovascular invasion (LVI). Recent retrospective series showed that up to 59% of preoperative low risk PCTs were upgraded to higher risk category after pathological examination. Current recommendations could potentially increase the need for re-operation, in terms of completion thyroidectomy (CT) and subsequent administration of RAI in order to reduce the risk of LRR. Among the HRFs, no preoperative clinical parameter is a predictor of nodal disease. However, occult lymph node metastases (LNMs) may be found in 31-62% of patients subjected to prophylactic CND (p-CND). The risk of complications (hypoparathyroidism and laryngeal nerve injury) is the main matter against bilateral p-CND in unifocal node negative PCT. According to a recent systematic review, basing on prevalence of occult central LNM by tumor size, ipsilateral CND (I-CND) may be justified in all PTC patients. Since isolated contralateral metastases are rare, a routine use of frozen section examination (FSE) of I-CND may allow a more accurate staging with a reduction of morbidity. Although p-CND is not usually recommended in patients with clinically unifocal cT1b/T2 node negative PTC, we supposed that the evaluation of LN status through FSE of I-CND may significantly contribute to risk stratification and consequently to modulate the extension of surgical treatment. In this retrospective study we aim to evaluate the result of this strategy to intraoperatively identify patients who may benefit from TT with bilateral CND (B-CND), reducing the need of second step CT and, theoretically, the risk of LRR. Among 4176 patients who underwent thyroidectomy for malignancy between September 2014 and September 2023 at Fondazione Policlinico Universitario A. Gemelli - Rome, we identified 110 patients scheduled for TL plus I-CND for clinically intrathyroidal unifocal cT1b/small cT2 node negative PTC. Every patient was informed of the risks and benefits of TL and TT, based on available guidelines. Inclusion criteria were: age\>18; classic papillary carcinoma and variants; clinically unifocal and intrathyroidal PTC; clinical tumor size \>1 cm and ≤3 cm; no clinical evidence of LN involvement. Exclusion criteria were: age \< 18 years; prior head or neck irradiation; family history of thyroid carcinoma; clinical evidence of multifocality, extrathyroidal extension or LN metastases; follow-up \< 6 months.