Papillary thyroid carcinoma: different clinical behavior among pT3 tumors

Surgical management of T1/T2 node-negative papillary thyroid cancer with tall cell histology: Is lobectomy enough?

BACKGROUND

The tall cell variant of papillary thyroid carcinoma has traditionally been treated more aggressively than classic papillary thyroid carcinoma. However, this may not be justified in patients with T1/T2 tall cell variant node-negative tumors.

METHODS

We evaluated well-differentiated thyroid cancers treated surgically between 1985 and 2015 at our institution. We compared patients undergoing lobectomy for node-negative T1/T2 tall cell variant tumors with the same cohort with classic papillary thyroid carcinoma. Patients who underwent early planned completion thyroidectomy were excluded. Tall cell variant tumors were defined as those with ≥30% tall cells. Survival and recurrence outcomes were determined by the Kaplan-Meier method and groups compared using the log-rank test.

RESULTS

Thyroid lobectomy was performed for T1/T2 N0X disease in 70 (15%) tall cell cases and 429 (23%) classic papillary thyroid carcinoma cases. There was no significant difference in 10-year overall survival (P = .56) or locoregional recurrence-free probability (P = .52). Disease-specific survival and local or central nodal recurrence-free probability were 100% in both groups. In 9 papillary thyroid carcinoma cases, subsequent contralateral lobe tumors developed, and in 5, lateral neck metastases developed. No recurrences were seen in the tall cell group.

CONCLUSION

T1 node-negative tumors with tall cell histology can be satisfactorily managed with thyroid lobectomy, with equivalent oncological outcomes to classic papillary thyroid carcinoma.

Characterization of the CpG island methylator phenotype subclass in papillary thyroid carcinoma

CpG island methylator phenotype (CIMP), characterized by the concurrent and widespread hypermethylation of a cluster of CpGs, has been reported to play an important role in carcinogenesis. Limited studies have explored the role of CIMP in papillary thyroid carcinomas (PTCs). Here, in genome-wide DNA methylation analysis of 350 primary PTCs from the Cancer Genome Atlas database that were assessed using the Illumina HumanMethylation450K platform, our study helps to identify two subtypes displayed markedly distinct DNA methylation levels, termed CIMP (high levels of DNA methylation) and nCIMP subgroup (low levels of DNA methylation). Interestingly, PTCs with CIMP tend to have a higher degree of malignancy, since this subtype was tightly associated with older age, advanced pathological stage, and lymph node metastasis (all P < 0.05). Differential methylation analysis showed a broad methylation gain in CIMP and subsequent generalized gene set testing analysis based on the significantly methylated probes in CIMP showed remarkable enrichment in epithelial mesenchymal transition and angiogenesis hallmark pathways, confirming that the CIMP phenotype may promote the tumor progression from another perspective. Analysis of tumor microenvironment showed that CIMP PTCs are in an immune-depletion status, which may affect the effectiveness of immunotherapy. Genetically, the significantly higher tumor mutation burden and copy number alteration both at the genome and focal level confirmed the genomic heterogeneity and chromosomal instability of CIMP. tumor Corresponding to the above findings, PTC patients with CIMP showed remarkable poor clinical outcome as compared to nCIMP regarding overall survival and progression-free survival. More importantly, CIMP was associated with worse survival independent of known prognostic factors.

Microscopic Extrathyroidal Extension Results in Increased Rate of Tumor Recurrence and Is an Independent Predictor of Patient's Outcome in Middle Eastern Papillary Thyroid Carcinoma

BACKGROUND

Papillary Thyroid Cancer (PTC) is the most common endocrine malignancy, with recurrence rate as high as 30%. A great deal of controversy surrounds the significance of microscopic extrathyroidal extension (m-ETE) as a prognostic factor. The most recent edition (8th) of American Joint Committee on Cancer (AJCC) staging system has removed m-ETE from the definition of pT3, which suggests that m-ETE may lack prognostic impact in PTC patients. Moreover, data about m-ETE prevalence and clinical impact on Middle Eastern PTC remains unknown. We therefore investigate the prevalence of m-ETE and its clinico-pathological correlation and prognostic impact in Middle Eastern PTC. We also compared the AJCC 7th and 8th staging systems and their prognostic performance.

METHODS

PTCs from 1430 consecutive adult (> 18 years) patients from single tertiary care hospital were included in this study. A retrospective analysis of PTC patients' survival and recurrence were compared between AJCC 8th and AJCC 7th staging systems using Proportion of Variation Explained (PVE) and Harrell's C-index.

RESULTS

Median follow up of the study cohort was 9.3 years. 31.2% (446/1430) of patients had m-ETE. In the overall cohort, m-ETE was associated with multiple adverse features such as older age (p < 0.0001), male sex (p = 0.0245), tall cell variant (p < 0.0001), bilateral tumors (p < 0.0001), multifocality (p < 0.0001), lymphovascular invasion (p < 0.0001), lymph node metastasis (p < 0.0001), distant metastasis (p = 0.0166), tumor recurrence (p < 0.0001), radioactive iodine refractoriness (p < 0.0001), BRAF mutation (p < 0.0001) and reduced recurrence-free survival (RFS; HR = 1.75; 95% CI = 1.30 - 2.35; p < 0.0001) irrespective of tumor size. Of the 611 patients with T3 disease based on AJCC 7th edition, 359 (58.8%) were down-staged in AJCC 8th edition classification. Overall, the prognostic performance of AJCC 8th edition was inferior to AJCC 7th on the basis of lower PVE (3.04% vs. 3.73%) and lower C-index (0.40 vs. 0.48).

CONCLUSIONS

In Middle Eastern PTC, m-ETE is significantly associated with compromised survival and acts as an independent predictor of RFS. Given these findings, m-ETE should be included in the thyroid cancer treatment guidelines.

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

Simple Summary

The aim of our retrospective study was to evaluate the impact of minimal extrathyroidal extension on early response rate after (adjuvant) initial radioactive iodine therapy in patients with papillary thyroid cancer (PTC). We found that response rates after radioactive iodine (RAI) therapy in PTC patients were achieved irrespective of minimal extrathyroidal extension (mETE). Nonetheless, the risk of lymph node metastases involvement was significantly higher in the mETE patient group.

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.

Small papillary thyroid carcinoma with minimal extrathyroidal extension should be managed as ATA low-risk tumor

PURPOSE

According to American Thyroid Association (ATA) guideline, papillary thyroid cancer (PTC) with minimal extrathyroidal extension (mETE) is classified at "intermediate risk" of persistent/recurrent disease. However, the impact of mETE per se on patients' outcome is not fully understood. The aim of our study was to evaluate the prognostic significance of mETE in patients with PTC not submitted to therapeutic or prophylactic lymph node dissection, according to tumor size and other prognostic factors.

PATIENTS AND METHODS

We retrospectively evaluated a total of 514 PTC patients: 127 (24.7%) had mETE (pT3Nx) and 387 (75.3%) had negative margins (pT1-2Nx). At a median follow-up of 9.1 years, patients were divided in two groups: patients with "good outcome" (no evidence of disease) and patients with "poor outcome" (persistent structural disease or recurrent disease or tumor-related death).

RESULTS

The rate of patients with "poor outcome" was significantly higher in patients with mETE compared with patients with negative margins (11.8 versus 5.1%; OR 2.4576, 95% CI 1.2178-4.9594, p = 0.01). However, mETE was significantly associated with poor outcome only in patients with tumors larger than 1.5 cm.

CONCLUSIONS

mETE is an unfavorable prognostic factor in tumors larger than 1.5 cm, suggesting that, in the absence of other unfavorable characteristics, smaller tumors with mETE should be classified and managed as "low risk" tumors.

Effect of Tumor Size and Minimal Extrathyroidal Extension in Patients with Differentiated Thyroid Cancer

INTRODUCTION

Risk-stratified treatment strategies have become a focus in the treatment of differentiated thyroid cancer (DTC). In the 2015 American Thyroid Association treatment guidelines, adjuvant treatment with radioactive iodine (RAI) is considered in the presence of minimal extrathyroidal extension (mETE). This study aimed to investigate the prognostic significance of mETE and tumor size in patients with DTC.

METHODS

A retrospective review was undertaken of 2323 consecutive patients treated surgically for T1-T3 (defined per seventh edition of the American Joint Committee on Cancer staging criteria) and M0 DTC from 2000 to 2015 at The University of Texas MD Anderson Cancer Center. Patients were divided into four groups according to the size of the tumor (≤4 cm vs. >4 cm) and the presence of mETE. Predictors of disease-free survival (DFS), disease-specific survival, locoregional failure (LRF), and distant metastatic failure (DMF) were compared using the log-rank test and Cox's proportional hazards models.

RESULTS

There were only seven DTC-related deaths, limiting the clinical significance of the analysis, especially of overall and disease-specific survival. Following multivariate analysis, patients with tumors >4 cm did worse than patients with tumors ≤4 cm with respect to DFS (group 3 [>4 cm without mETE] adjusted hazard ratio (HR_adj) = 2.1 [confidence interval (CI) 1.1-3.8]; group 4 [>4 cm with mETE] HR_adj = 2.9 [CI 1.6-5.1]). However, patients did not differ according to DFS, regardless of the presence of mETE within each size category (group 2 [≤4 cm with mETE] vs. group 1 [≤4 cm without mETE] HR_adj = 1.3 [CI 0.9-1.8]; group 4 [>4 cm without mETE] vs. group 3 [>4 cm with mETE] HR_adj = 1.0 [CI 0.5-2.3]). For LRF and DMF, size but not mETE was also an independent risk factor.

CONCLUSION

Tumor size, but not the presence of mETE, was an independent predictor of DFS, LRF, and DMF in DTC.

Heterogeneous Prognoses for pT3 Papillary Thyroid Carcinomas and Impact of Delayed Risk Stratification

BACKGROUND

Papillary thyroid carcinomas (PTC) in the pT3 category constitute a heterogeneous group of tumors with a variable risk of recurrence. The objectives of this study were (i) to estimate disease-free survival (DFS) and identify prognostic factors associated with recurrence in a cohort of pT3 PTC, and (ii) to evaluate the concept of delayed risk stratification in a cohort of pT3 tumors.

METHODS

A total of 560 patients with pT3 PTC, treated and followed at the authors' institution, were studied. They were divided into three groups: group 1, pT3 ≤10 mm; group 2, pT3 >10 mm with extrathyroidal invasion (ETI); and group 3, pT3 due to a tumor size >4 cm. DFS was estimated using the Kaplan-Meier method, and associated prognostic features were studied in univariate and multivariate Cox model-based analyses in each group. Then, DFS was studied for each group according to the six- to eight-month status (remission or not).

RESULTS

DFS at 10 years was 75% for the entire cohort and was 89%, 67%, and 82% in groups 1, 2, and 3, respectively (p < 0.0001). Multivariate analysis identified three factors significantly associated with reduced DFS: lymph node (LN) involvement, male sex, and group 2 (>1 cm with ETI). A trend toward a worse prognosis in patients with pT3 N0/Nx PTC >10 mm with ETI was found in comparison with the other pT3 N0/Nx patients. When the six- to eight-month checkup was normal, the DFS at 10 years increased to 98%, 96%, and 91% in groups 1-3, respectively. Furthermore, in this case, initial LN involvement no longer seemed to affect the prognosis in those groups.

CONCLUSION

PTC ≤10 mm with ETI and large tumors >4 cm without ETI both have a low-recurrence risk when there are no adverse associated prognostic features such as LN involvement. LN involvement, especially in the lateral compartment (N1b), is a strong prognostic factor of recurrence in pT3 PTC. Delayed risk stratification can be applied in pT3 PTC patients. Those cured at the first checkup, including those with limited LN involvement, have excellent outcomes, which should prompt clinicians to adapt subsequent management accordingly.

Prognostic indicators for papillary thyroid carcinoma

Differentiated thyroid cancer (DTC) includes more than 90% of all thyroid carcinoma and its incidence is growing, mainly due to an increase in the incidence of papillary thyroid cancer (PTC) for the widespread use of neck ultrasonography. Areas covered: Several prognostic factors should be considered during the management of PTC in order to provide the most effective treatment. The most important prognostic factors in PTC include personal and pathological features such as patient's age, gender, hystotype, tumor size, extrathyroidal extension, lymph node involvement, presence of local or distant metastases and molecular analyses. We performed a search in the PubMed database for studies published in English since 1960 using the terms: 'thyroid cancer', 'prognostic factors', 'age', 'gender', 'hystotype', 'tumor size', 'extrathyroidal extension', 'lymph node', 'metastases' and 'molecular analyses'. Expert commentary: Prognostic factors can guide clinicians during the treatment and follow-up of DTC patients, but it is now evident that the risk of recurrence or death must be evaluated periodically, on the basis of individual risk, according to the response to initial therapy or the subsequent therapy required during follow-up.