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

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

Minimal extrathyroid extension (mETE) effect on papillary thyroid carcinoma (PC) prognosis is still debated even more so now that this factor has been removed in the 8th AJCC Edition, supporting the hypothesis that mETE is not associated with aggressive tumors. We retrospectively enrolled 91 PC patients (Group 1) submitted to total thyroidectomy and radioiodine ablation. At the time of the primary tumor surgery, mETE was ascertained in all patients with no other risk factors, such as multifocality, vascular invasion, neck and distant metastases, and aggressive histological variants. As controls, 205 consecutive matched PC patients (Group 2) without mETE and the aforementioned risk factors were enrolled. During the follow-up (average 8 years), 16/91 (17.58%) Group 1 patients and 15/205 (7.32%) Group 2 patients developed metastases (p = 0.0078). Cox regression analysis showed an increased risk of metastases in patients with mETE (HR: 2.58 (95% CI 1.28-5.22) p = 0.008). Disease-free survival (DFS) was significantly lower in patients with mETE than in controls (p = 0.0059). The present study seems to demonstrate that mETE can be associated with an aggressive PC and can be considered, even alone without other risk factors, an independent factor of unfavorable DFS. Thus, by excluding mETE in the 8th AJCC Edition, patient care and management could be compromised.

Current practice in intermediate risk differentiated thyroid cancer - a review

Although the overall prognosis for differentiated thyroid cancer (DTC) is excellent, a subset of patients will experience disease recurrence or may not respond to standard treatments. In recent years, DTC management has become more personalized in order to enhance treatment efficacy and avoid unnecessary interventions.In this context, major guidelines recommend post-surgery staging to assess the risk of disease persistence, recurrence, and mortality. Consequently, risk stratification becomes pivotal in determining the necessity of postoperative adjuvant therapy, which may include radioiodine therapy (RIT), the degree of TSH suppression, additional imaging studies, and the frequency of follow-up.However, the intermediate risk of recurrence is a highly heterogeneous category that encompasses various risk criteria, often combined, resulting in varying degrees of aggressiveness and a recurrence risk ranging from 5 to 20%. Furthermore, there is not enough long-term prognosis data for these patients. Unlike low- and high-risk DTC, the available literature is contradictory, and there is no consensus regarding adjuvant therapy.We aim to provide an overview of intermediate-risk differentiated thyroid cancer, focusing on criteria to consider when deciding on adjuvant therapy in the current context of personalized approach, including molecular analysis to enhance the accuracy of patient management.

Post-Surgical Indications to Radioiodine Treatment and Potential Risk Factors for Post-Treatment Recurrence in Patients with Intermediate-Risk Differentiated Thyroid Carcinoma

In this multicentric retrospective observational study, we investigated the potential risk factors for radioiodine (RAI) indication and the post-treatment recurrence of intermediate-risk differentiated thyroid cancer (DTC) 1 and 3 years from diagnosis. We included 121 patients who underwent thyroidectomy for intermediate-risk DTC. The 92 patients (76.0%) who underwent RAI treatment had a higher prevalence of extra-thyroid micro-extension (mETE) (p = 0.03), pT3 staging (p = 0.03) and recourse to therapeutic central (p = 0.04) and lateral (p = 0.01) neck dissection, as well as higher numbers (p = 0.02) and greater dimensions (p = 0.01) of lymph node metastases, compared with untreated patients. Relapse was observed in 18.1% and 20.7% of cases 1 and 3 years from diagnosis, respectively, with no significant differences between groups. A lower age at diagnosis (p = 0.03) and higher levels of stimulated thyroglobulin (Tg) (p = 0.04) emerged as the only independent risk factors for tumour relapse at 1 year. Tumour relapse at 3 years was only independently predicted by the presence of tumour relapse at 1 year (p = 0.04). In conclusion, mETE, pT3 and the presence of large, multiple or clinically evident lymph node metastases represent the main indicators for referring patients to RAI treatment. Early recurrence may be considered the most relevant factor when planning further surveillance.

Minimal Extrathyroidal Extension in Predicting 1-Year Outcomes: A Longitudinal Multicenter Study of Low-to-Intermediate-Risk Papillary Thyroid Carcinoma (ITCO#4)

Background: The role of minimal extrathyroidal extension (mETE) as a risk factor for persistent papillary thyroid carcinoma (PTC) is still debated. The aims of this study were to assess the clinical impact of mETE as a predictor of worse initial treatment response in PTC patients and to verify the impact of radioiodine therapy after surgery in patients with mETE. Methods: We reviewed all records in the Italian Thyroid Cancer Observatory database and selected 2237 consecutive patients with PTC who satisfied the inclusion criteria (PTC with no lymph node metastases and at least 1 year of follow-up). For each case, we considered initial surgery, histological variant of PTC, tumor diameter, recurrence risk class according to the American Thyroid Association (ATA) risk stratification system, use of radioiodine therapy, and initial therapy response, as suggested by ATA guidelines. Results: At 1-year follow-up, 1831 patients (81.8%) had an excellent response, 296 (13.2%) had an indeterminate response, 55 (2.5%) had a biochemical incomplete response, and 55 (2.5%) had a structural incomplete response. Statistical analysis suggested that mETE (odds ratio [OR] 1.16, p = 0.65), tumor size >2 cm (OR 1.45, p = 0.34), aggressive PTC histology (OR 0.55, p = 0.15), and age at diagnosis (OR 0.90, p = 0.32) were not significant risk factors for a worse initial therapy response. When evaluating the combination of mETE, tumor size, and aggressive PTC histology, the presence of mETE with a >2 cm tumor was significantly associated with a worse outcome (OR 5.27 [95% confidence interval], p = 0.014). The role of radioiodine ablation in patients with mETE was also evaluated. When considering radioiodine treatment, propensity score-based matching was performed, and no significant differences were found between treated and nontreated patients (p = 0.24). Conclusions: This study failed to show the prognostic value of mETE in predicting initial therapy response in a large cohort of PTC patients without lymph node metastases. The study suggests that the combination of tumor diameter and mETE can be used as a reliable prognostic factor for persistence and could be easily applied in clinical practice to manage PTC patients with low-to-intermediate risk of recurrent/persistent disease.

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

¹³¹I Single-photon emission computerized tomography/computerized tomography (SPECT/CT) in the management of patients thyroidectomized for differentiated thyroid carcinoma (DTC) was further investigated. Retrospectively, 106 consecutive DTC patients were enrolled at the first radioiodine ablation, 24 at high risk (H), 61 at low risk (L) and 21 at very low risk (VL). ¹³¹I whole-body scan (WBS) and SPECT/CT were performed after therapeutic doses using a hybrid dual-head gamma camera. At ablation, SPECT/CT correctly classified 49 metastases in 17/106 patients with a significantly (p < 0.001) more elevated number than WBS which evidenced 32/49 foci in 13/17 cases. In this case, 86/106 patients could be monitored in the follow-up including 13/17 cases with metastases already at post-therapeutic scans. SPECT/CT after radioiodine diagnostic doses more correctly than WBS ascertained disease progression in 4/13 patients, stable disease in other 4/13 cases and disease improvement in the remaining 5/13 cases. Further 13/86 patients with only residues at post-therapeutic scans showed at SPECT/CT 16 neck lymph node (LN) metastases, three unclear and 13 occult at WBS. Significant involvement of some tissue risk factors with metastasis appearance was observed, such as minimal extrathyroid tumor extension and neck LN metastases. These risk factors should be carefully considered in DTC patient follow-up where ¹³¹I-SPECT/CT routinely use is suggested as a support tool of WBS.

Minimal extrathyroid extension in papillary micro carcinoma of the thyroid is an independent risk factor for relapse through lymph node and distant metastases

Aims: Minimal extrathyroid extension (mETE) is no longer considered in the new 8th edition of the AJCC/UICC staging system. Therefore, papillary thyroid microcarcinoma with mETE previously staged as pT3 will now be staged as pT1a and most likely not receive adjuvant radioiodine therapy. However, it remains unclear if mETE is associated with higher aggressiveness in papillary thyroid microcarcinoma. Therefore, the aim of this study was to investigate if mETE is associated with higher risk of lymph node or distant metastases. Methods: 721 patients with thyroid papillary microcarcinoma presenting at our department for postoperative counseling from 05/1983 to 8/2012 were included in this retrospective analysis (median follow-up time 9.30 years). The impact of mETE on the presence of lymph node metastases at thyroidectomy and relapse through lymph node and distant metastases was assessed by logistic regression and Fine-Gray model analyses. Results: 10.7% (n = 77) of patients had mETE. mETE was an independent risk factor for lymph node metastases at thyroidectomy with an adjusted odds ratio of 4.33 (95%CI: 2.02-9.60, p<0.001) in multivariable analysis. Patients with mETE had significantly more relapses through lymph node (over 5 years: 13.1% vs. 1.25%; P < 0.001) and distant metastases (over 5 years: 7.8% vs. 1.1%; P < 0.001) compared to patients without mETE. mETE was an independent risk factor for relapse through lymph node and distant metastases in multivariable analysis (hazard ratio: 7.78, 95%CI: 2.87-21.16, p< 0.001 and 4.09, 95%CI: 1.25-13.36, P = 0.020). Conclusion: mETE is a statistically significant and independent risk factor for relapse through lymph node and distant metastases in papillary microcarcinoma. Therefore, future studies should evaluate, if patients with mETE and microcarcinoma might benefit from intensified surveillance and therapy.

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

OBJECTIVE

Children with papillary thyroid cancer (PTC) have a higher invasive rate and distant metastasis rate, but the mortality rate is lower with unknown reasons. The majority of PTC cases comprise classical papillary thyroid carcinoma (CPTC) and follicular variant papillary thyroid carcinoma (FVPTC). This study aimed to determine the relationship between histopathological subtype and rate of distant metastasis and investigate factors influencing distant metastasis in pediatric PTC.

METHODS

A total of 102,981 PTC patients were recruited from SEER registry, 2004-2015. Proportion of distant metastasis between children (≤18 years) and adults with different histopathological subtypes was compared by propensity score matching. The cut-off age for distant metastasis in children was calculated by receiver operating characteristic (ROC) curve, and the risk factors for distant metastasis in pediatric patients were analyzed by logistic regression models.

RESULTS

Among the 1,484 children and 101,497 adults included in the study, the incidence of CPTC patients with distant metastasis in children was higher than that in adults (p<0.001). The ROC curve was calculated, which yielded a cut-off age for distant metastasis in CPTC children as 16 years old. In CPTC, the proportion of young children (2-16 years) with distant metastasis was higher than that of adolescents (17-18 years) and adults (>18 years) (both p<0.001). While there was no such trend in FVPTC. In young children (2-16 years), the incidence of CPTC with distant metastasis was higher than FVPTC (p=0.006). There was no difference between the proportion of CPTC and FVPTC with distant metastasis in adolescents (17-18 years) and adults. Logistic regression models revealed that extrathyroidal extension, lymph node metastasis and CPTC histopathological subtype were risk factors for distant metastasis in young children aged 2 -16 years.

CONCLUSIONS

In CPTC, the incidence of distant metastasis in young children (2-16 years) was significantly higher than that in adolescents (17-18 years) and adults (>18 years). In patients with distant metastasis aged 2-16 years, the proportion of CPTC was higer than that of FVPTC. Extrathyroidal extension, lymph node metastasis, and CPTC histopathological subtype were risk factors for distant metastasis in young children aged 2-16 years.