Effects of the Minimal Extrathyroidal Extension on Early Response Rates after (Adjuvant) Initial Radioactive Iodine Therapy in PTC Patients

Abstract

Background: Extrathyroidal extension of differentiated thyroid cancer is a poor outcome factor but seems to be less significant in minimal extrathyroidal extension (mETE). However, the impact of mETE on response rate after (adjuvant) initial radioactive iodine (RAI) therapy remains unclear. We therefore compared response rates of patients with classical and follicular variants of papillary thyroid cancer (PTC) according to the updated eighth tumor-node-metastasis (TNM) classification to a control group. Methods: 455 patients with T3 (primary tumor > 4 cm) PTC according to the seventh classification who underwent total thyroidectomy followed by RAI therapy were screened. Patients formerly classified as T3 PTC solely due to mETE were reclassified into patients with T1 (primary tumor ≤ 2 cm) or T2 (primary tumor > 2 cm but ≤ 4 cm) +mETE and compared to a control group of T1/T2 −mETE PTC patients. Results: 138/455 patients were reclassified as T1/2 +mETE and compared to 317/455 T1/T2 −mETE control patients. At initial presentation, +mETE patients showed significantly higher rates of cervical lymph node metastases (p-value 0.001). Response rates were comparable in both groups (p-value n.s.). N1a/N1b-stage (Hazard ratio, HR 0.716; 95% CI 0.536–0.956, p-value 0.024) was identified as an independent prognostic factor for lower response rates. Conclusion: Response rates after RAI therapy were comparable in PTC patients irrespective of mETE but with higher rates of lymph node metastases.

The Diagnostic Usefulness of 131I-SPECT/CT at Both Radioiodine Ablation and during Long-Term Follow-Up in Patients Thyroidectomized for Differentiated Thyroid Carcinoma: Analysis of Tissue Risk Factors Ascertained at Surgery and Correlated with Metastasis Appearance

“…Concerning the 10/30 (33.3%) patients who had mETE at surgery, it resulted that also this risk factor is associated with a poor prognosis (p = 0.027) and at the univariate analysis the affected patients showed an increased risk for metastasis appearance after thyroidectomy, OR 3.25 (95% CI 1.13-9.41), p-value = 0.03. These results referring to the few cases of the present study confirm previous data reported in the literature [9,[17][18][19][20][21] while differing from others [13,[22][23][24][25][26][27][28]. Moreover, the primary tumor size of mETE patients was >15 mm in 9/10 (90%) of cases and <10 mm in the remaining case, the latter being a microcarcinoma (8 mm).…”

“…Moreover, extrathyroid tumor extension (ETE) has been recognized as a prognostic factor of DTC [13,14]. However, while extended ETE (eETE) proved a significant worsening of the prognosis [13][14][15][16], the impact of minimal ETE (mETE) is controversial presenting an increased risk of recurrence in some studies [8,[17][18][19][20][21] and vice versa reporting no significant impact on disease-free survival in other studies [13,[22][23][24][25][26][27][28]. DTC has slow growth and recurrences and metastases can appear and become clinically evident even many years later; thus, the carcinomas can require a long-term follow-up to guarantee careful surveillance of the affected patients [10,29].…”

High Incidence of Distant Metastasis Is Associated With Histopathological Subtype of Pediatric Papillary Thyroid Cancer - a Retrospective Analysis Based on SEER

“…However, despite these similarities, minimal ETE and aggressive histopathological features, such as thyroid capsule infiltration, are significantly more common in CPTC than in FVPTC ( 11 ). Besides, patients with mETE showed significantly higher rates of lymph node metastases in the neck ( 12 ) and all levels of ETE, including microscopic ETE, were associated with increased risk for lymph node metastasis and DM ( 13 ). Thus, we propose the following hypothesis: The high DM rate in pediatric PTC aged less than 18 years old is associated with histopathological subtype.…”

Minimal Extrathyroid Extension (mETE) as the Only Risk Factor in Patients with Papillary Thyroid Carcinoma (PC): Its Clinical Impact on Recurrence and Outcome during Long-Term Follow-Up

“…In particular, the study showed that age > 55 years did not have a significant impact on the risk of disease. In other studies, it has been observed that radioiodine therapy had a similar response rate in PTC patients regardless of the presence of mETE, although there was a high frequency of LN metastases [37]. According to the results obtained by other authors who reported that mETE increases the risk of recurrence in DTC patients, it has been observed that the absolute increase is small and, in addition, mETE has no impact on disease-related mortality [38].…”