The significance of unrecognized histological high-risk features on response to therapy in papillary thyroid carcinoma measuring 1-4 cm: implications for completion thyroidectomy following lobectomy

A clinically useful and biologically informative genomic classifier for papillary thyroid cancer

Clinical management of papillary thyroid cancer depends on estimations of prognosis. Standard care, which relies on prognostication based on clinicopathologic features, is inaccurate. We applied a machine learning algorithm (HighLifeR) to 502 cases annotated by The Cancer Genome Atlas Project to derive an accurate molecular prognostic classifier. Unsupervised analysis of the 82 genes that were most closely associated with recurrence after surgery enabled the identification of three unique molecular subtypes. One subtype had a high recurrence rate, an immunosuppressed microenvironment, and enrichment of the EZH2-HOTAIR pathway. Two other unique molecular subtypes with a lower rate of recurrence were identified, including one subtype with a paucity of BRAFV600E mutations and a high rate of RAS mutations. The genomic risk classifier, in addition to tumor size and lymph node status, enabled effective prognostication that outperformed the American Thyroid Association clinical risk stratification. The genomic classifier we derived can potentially be applied preoperatively to direct clinical decision-making. Distinct biological features of molecular subtypes also have implications regarding sensitivity to radioactive iodine, EZH2 inhibitors, and immune checkpoint inhibitors.

Molecular Testing Predicts Incomplete Response to Initial Therapy in Differentiated Thyroid Carcinoma without Lateral Neck or Distant Metastasis at Presentation: Retrospective Cohort Study

BACKGROUND

Molecular testing (MT) is emerging as a potential prognostic factor that can be available before treatment of differentiated thyroid carcinoma begins. Among patients eligible for either lobectomy or total thyroidectomy as their initial therapy, our study aim was to assess (1) if conventionally available preoperative factors are associated with incomplete response to initial therapy, and (2) if molecular testing (MT) results can be a surrogate for the ATA Risk Stratification System (RSS) to estimate risk of recurrence.

METHODS

The data of consecutive thyroid cancer patients without preoperative lateral neck disease or distant metastasis who underwent index thyroidectomy between November 1, 2017 and October 31, 2021 were reviewed. Logistic regression models including preoperative variables such as MT and/or the postoperatively available RSS were constructed to predict disease recurrence, either structural or biochemical. Model discrimination using the c-statistic and goodness-of-fit were compared.

RESULTS

Among 945 patients studied, 50 (5.2%) recurred with 18-month median follow up. Recurrences were detected in 17 (2.9%), 20 (6.7%), and 13 (22.8%) patients with RSS-Low, -Intermediate, and -High cancers, respectively (p<0.001). In multivariable analysis, only tumor size was associated with recurrence (OR 1.3, 95% CI 1.1-1.5). In a different model analyzing 440 (46.6%) patients with available MT results, recurrence was associated with both larger tumor size (OR 1.4, 95% CI 1.1-1.8) and MT results (p<0.001). Including MT improved the c-statistic by 27%, which was statistically no different than the model incorporating only the RSS (p=0.15).

CONCLUSIONS

Disease recurrence was observed across all ATA RSS categories in short-term follow-up, and tumor size was the only conventional preoperative factor associated with recurrence. When MT results were incorporated, they not only improved predictive ability beyond tumor size alone, but also yielded similar ability as the gold standard ATA RSS. Thus, MT results might aid the development of novel preoperative risk stratification algorithms.

Risk staging with prophylactic unilateral central neck dissection in low-risk papillary thyroid carcinoma

OBJECTIVE

Current guidelines favor thyroid lobectomy for intrathyroidal cT1bT2cN0 papillary thyroid carcinoma. Prophylactic neck dissection (PND) is not recommended for these low-risk tumors due to the lack of high-level evidence on improvement in outcomes, but the information from PND may be used for staging. The aim of this study was to evaluate the rate of upstaging with ipsilateral PND.

MATERIALS AND METHODS

Retrospective study of patients with intrathyroidal unifocal cT1bT2cN0 papillary thyroid carcinoma from 2008 to 2021. All patients underwent total thyroidectomy and PND. Tumors were classified as low or intermediate risk based on the information from pathological analysis of the primary tumor and then from adding the analysis of the lymph nodes. The difference between the tumor-only and the PND-added risk staging was evaluated.

RESULTS

Three hundred three patients (241 women, median age 45, median tumor size 17 mm) were included. Microscopic extrathyroidal extension was found in 23.4%, aggressive histology in 6.6%, vascular invasion in 29.3%, and lymph node metastases in 37.3%. One hundred ten patients (36.3%) were intermediate-risk based on the primary tumor. An additional 26 (8.6%) were upstaged to intermediate-risk based on the ipsilateral PND and 2% based on the contralateral PND. Kaplan-Meier 10-year event-free survival in tumors upstaged with ipsilateral PND was not statistically different from intermediate-risk tumors based on the primary tumor characteristics (92% versus 90.9%, Log Rank p = 0.943).

CONCLUSIONS

Ipsilateral PND upstaged low-risk cT1bT2cN0 patients to intermediate risk in only 8.6% of cases, and contralateral PND in an additional 2%. Routinely performing PND may not be warranted.

Lobo-isthmectomy in the management of differentiated thyroid cancer

We have recently witnessed a rapid increase in the incidence of differentiated thyroid carcinoma (DTC), particularly low and very low-risk papillary thyroid carcinoma. Simultaneously, the number of cancer-related deaths has remained stable for more than 30 years. Such an indolent nature and long-term survival prompted researchers and experts to an ongoing discussion on the adequacy of DTC management to avoid, on the one hand, the overtreatment of low-risk cases and, on the other hand, the undertreatment of highly aggressive ones.The most recent guidelines of the American Thyroid Association (ATA GL) moved primary thyroid surgery in DTC towards a less aggressive approach by making lobectomy an option for patients with intrathyroidal low-risk DTC tumors up to 4 cm in diameter without evidence of extrathyroidal extension or lymph node metastases. It was one of the key changes in DTC management proposed by the ATA in 2015.Following the introduction of the 2015 ATA GL, the role of thyroid lobectomy in DTC management has slowly become increasingly important. The data coming from analyses of the large databases and retrospective studies prove that a less extensive surgical approach, even if in some reports it was related to a slight increase of the risk of recurrence, did not show a negative impact on disease-specific and overall survival in T1T2N0M0 low-risk DTC. There is no doubt that making thyroid lobectomy an option for low-risk papillary and follicular carcinomas was an essential step toward the de-escalation of treatment in thyroid carcinoma.This review summarizes the current recommendations and evidence-based data supporting the necessity of de-escalation of primary thyroid surgery in low-risk DTC. It also discusses the controversies raised by introducing new ATA guidelines and tries to resolve some open questions.

Current Controversies in Low-Risk Differentiated Thyroid Cancer: Reducing Overtreatment in an Era of Overdiagnosis

CONTEXT

Low-risk differentiated thyroid cancer (DTC) is overdiagnosed, but true incidence has increased as well. Owing to its excellent prognosis with low morbidity and mortality, balancing treatment risks with risks of disease progression can be challenging, leading to several areas of controversy.

EVIDENCE ACQUISITION

This mini-review is an overview of controversies and difficult decisions around the management of all stages of low-risk DTC, from diagnosis through treatment and follow-up. In particular, overdiagnosis, active surveillance vs surgery, extent of surgery, radioactive iodine (RAI) treatment, thyrotropin suppression, and postoperative surveillance are discussed.

EVIDENCE SYNTHESIS

Recommendations regarding the diagnosis of DTC, the extent of treatment for low-risk DTC patients, and the intensity of posttreatment follow-up have all changed substantially in the past decade. While overdiagnosis remains a problem, there has been a true increase in incidence as well. Treatment options range from active surveillance of small tumors to total thyroidectomy followed by RAI in select cases. Recommendations for long-term surveillance frequency and duration are similarly broad.

CONCLUSION

Clinicians and patients must approach each case in a personalized and nuanced fashion to select the appropriate extent of treatment on an individual basis. In areas of evidential equipoise, data regarding patient-centered outcomes may help guide decision-making.

Impact of completion thyroidectomy on postoperative recovery in patients with differentiated thyroid cancer

While an increasing number of patients now undergo lobectomy for low-risk differentiated thyroid cancer, a subset of patients require completion thyroidectomy to facilitate radioactive iodine therapy. Completion thyroidectomy is generally as safe as the initial operation, but a previous study showed that a longer hospitalization is required for completion thyroidectomy. In this study, we reviewed 61 consecutive patients who had been treated with an initial lobectomy and subsequent completion thyroidectomy at our institution from 2012 to 2021. We detected a changepoint in 2016 for the proportion of patients who were treated with a thyroid lobectomy (Pettitt's test P = 0.049). The rate of completion thyroidectomy remained stable throughout the study period. There was no difference in operating time, intraoperative blood loss, perioperative drop in calcium levels, and postoperative hospital stay between surgeries. The patients reported higher pain scores on the day of operation (P = 0.007) and the postoperative day 1 (P = 0.022). Occult papillary microcarcinomas were identified in the contralateral thyroid lobe in 13 (21%) patients. Multifocality was the only predictor for residual malignancy in multivariate regression. In conclusion, patients with differentiated thyroid cancer experienced more pain in the immediate postoperative period following completion thyroidectomy. Hospital stays do not change with appropriate opioid-free pain control.

Cost-effectiveness analysis of molecular testing for cytologically indeterminate thyroid nodules

BACKGROUND

Thyroid nodules affect up to 65% of the population. Although fine needle aspirate (FNA) cytology is the gold standard for diagnosis, 15-30% of results are indeterminate. Molecular testing may aid in the diagnosis of nodules and potentially reduce unnecessary surgery. However, these tests are associated with significant costs. The objective of this study was to evaluate the cost-effectiveness of Afirma, a commercially available molecular test, in cytologically indeterminate thyroid nodules.

METHODS

The base case was a solitary thyroid nodule with no additional high-risk features and an indeterminate FNA. Decision tree analysis was performed from the single payer perspective with a 1-year time horizon. Costing data were collected through micro-costing methodology. A probabilistic sensitivity analysis was performed. The primary outcome was the incremental cost effectiveness ratio (ICER) of cost per thyroid surgery avoided.

RESULTS

Over 1 year, mean cost estimates were $8176.28 with 0.58 effectiveness for the molecular testing strategy and $6016.83 with 0.07 effectiveness for current standard management. The ICER was $4234.22 per surgery avoided. At a willingness-to-pay (WTP) threshold of $5000 per surgery avoided, molecular testing is cost-effective with 63% certainty.

CONCLUSION

This cost-effectiveness analysis suggests utilizing Afirma for indeterminate solitary thyroid nodules is a cost-effective strategy for avoiding unnecessary thyroid surgery. With a $5000 WTP threshold, molecular testing has a 63% chance of being the more cost-effective strategy. The cost effectiveness varies based on the cost of the molecular test and the value of Afirma for patients with indeterminate thyroid nodules depends on the WTP threshold to avoid unnecessary thyroid surgery.

Prognostic Factors for Excellent Response to Initial Therapy in Patients With Papillary Thyroid Cancer From a Prospective Multicenter Study

Prognostic factors for excellent response (ER) to initial therapy in patients with papillary thyroid cancer (PTC) have not been determined. In this study, we investigated the response to initial therapy in PTC patients and independent prognostic factors for ER in a prospective multicenter study in China. A total of 506 PTC patients from nine centers in China were enrolled in this study, all of whom underwent total or near total thyroidectomy with lymph node dissection and subsequent radioiodine therapy. Univariate and multivariable logistic regression analyses were carried out to determine the independent prognostic factors for ER. The optimal cutoff value of the number of metastatic lymph nodes for predicting ER was determined by the receiver operating characteristic curve. A total of 139 patients (27.5%) achieved ER after initial therapy. Extrathyroidal extension, the number of metastatic lymph nodes, and preablative-stimulated thyroglobulin (Ps-Tg) were independent risk factors for ER for the entire population. In a subgroup analysis, extrathyroidal extension and Ps-Tg were independent risk factors for ER in pathological N1a patients, while the number of metastatic lymph nodes and Ps-Tg were independent risk factors for ER in pathological N1b patients. The appropriate cutoff values of the number of metastatic lymph nodes in predicting ER were 5 and 13 for the entire population and pathological N1b PTC patients, respectively. PTC patients with more metastatic lymph nodes were more likely to fail to achieve ER. Extrathyroidal extension, the number of metastatic lymph nodes, and Ps-Tg were important prognostic factors for ER after initial therapy in PTC patients.

Adverse Histological Features of Differentiated Thyroid Cancer Are Commonly Found in Autopsy Studies: Implications for Treatment Guidelines

Background: While the popularity of lobectomy for differentiated thyroid cancer (DTC) has increased since the 2015 ATA (American Thyroid Association) guidelines, recent studies reported that adverse histological features (minimal extrathyroidal extension [mETE], multifocality, vascular invasion, and lymph node [LN] metastases) may be found in 30-60% of lobectomy specimens, questioning the validity of this approach. Aim: To assess the prevalence adverse histological features in occult DTC detected in autopsy studies. Methods: Meta-analysis of autopsy studies of the thyroid in subjects without known history of thyroid cancer. Results: Twenty-nine studies including 8750 subjects fulfilled the inclusion criteria, with incidentally discovered DTC in 740 autopsies (8.5%). Age was reported in 17 studies, with a median age of 61 years (range 41-68 years). Multifocality was reported in 27 studies with a calculated event rate of 28.2% ([CI 23.1-33.8], I² = 46.3%), with bilateral involvement in 18% [CI 12.6-25.1]. mETE was reported in 5 studies, with an event rate of 24.5% ([CI 9.3-50.7], I² = 88.5%), and the presence of LN metastases were reported in 13 studies with an event rate of 11% ([CI 6.1-19.1], I² = 69.5%). Vascular invasion was reported in seven studies with an event rate of 16% ([CI 4-47], I² = 86.8%). Of 25 studies with whole body autopsies (722 subjects), 3 cases of distant metastases were reported, of which 2 had fatal metastatic disease (where thyroid origin was not diagnosed before death), and 1 had occult disease. Conclusions: Adverse histological features including mETE, LN metastases, multifocality, and vascular invasion are common in occult DTC. When minimal in size, these adverse histological features do not seem to be markers of aggressive disease and may not be an indication for completion thyroidectomy or radioiodine therapy.

[De-escalation strategies in differentiated thyroid cancer]

Thyroid cancer runs the gamut from indolent micropapillary carcinoma to highly aggressive metastatic disease. Today, using prognostic algorithms, treatment and follow-up can be tailored to each patient in order to decrease overtreatment and over-medicalization of indolent disease. Active surveillance of papillary thyroid carcinoma less than 1cm avoids surgery and thyroid hormone replacement in a large proportion of patient whose tumors remain stable for years. Total thyroidectomy, once a dogma in the treatment of all thyroid cancer, is being supplanted by thyroid lobectomy for low-risk cancers, thereby decreasing the surgical risks involved and improving patients' quality of life. Indications for prophylactic central neck dissection, once mandatory, are now being adapted to the risk of cancer recurrence. Radioactive iodine therapy, also previously mandatory for all, is now only employed according to risk factors and expected outcomes. Follow-up is also being tailored to risk factors for recurrence, with less frequent visits and less use of ultrasound and scintigraphy. For more advanced disease, molecular therapies tailored to somatic mutations are opening opportunities for redifferentiation of aggressive tumors which become amenable to radioactive iodine therapy which carries fewer side effects than other systemic therapies. These advances in the management of thyroid cancer with a personalized approach and de-escalation of treatment and follow-up are improving the way we treat thyroid cancer, avoiding overtreatment and improving patients' quality of life.

The incidence of postoperative re-stratification for recurrence in well-differentiated thyroid cancer-a retrospective cohort study

Background

After diagnosing well-differentiated thyroid cancer (WDTC), assessment of the risk for disease-specific recurrence is essential for deciding between hemi-thyroidectomy (HT) and total thyroidectomy (TT). The American Thyroid Association (ATA) 2015 guidelines suggest that patients with 1-4 cm WDTC without suspicious features may be suitable for HT. Patients' preoperatively determined risk levels are re-stratified according to surgical and final histopathological findings. The incidence and clinical implications of high-risk features discovered postoperatively in patients with preoperatively determined low-risk WDTC are yet to be better defined.

Methods

Thyroidectomies performed in the Tel-Aviv Sourasky Medical Center (TASMC) [2006-2018] were included. Patients with 1-4 cm WDTC without evidence of positive cervical lymph nodes, invasion to adjacent structures, or high-risk cytology were considered at low risk for disease-specific recurrence-suitable for lobectomy. Patients were stratified according to their risk for disease-specific recurrence, pre- and postoperatively, and the rate of completion thyroidectomy was determined.

Results

In total, 301 (21%) patients were preoperatively stratified as low risk. Forty-six of them (15%) were re-stratified postoperatively as intermediate-to-high-risk. There were no significant differences in the characteristics of the patients who maintained their original stratification to patients who were upscaled to a higher risk level postoperatively.

Conclusions

We report a 15% rate of postoperative risk escalation of patients who required completion thyroidectomy according to current ATA guidelines. In our opinion, this rate of postoperative WDTC upscaling of risk requiring more radical surgery than originally planned, is acceptable. Meticulous preoperative personalized evaluation by an experienced multidisciplinary dedicated team is essential.

Less extensive surgery for low-risk papillary thyroid cancers post 2015 American Thyroid Association guidelines in an Australian tertiary centre

INTRODUCTION

The 2015 American Thyroid Association guidelines (ATA15) consider hemithyroidectomy (HT) a viable treatment option for low-risk papillary thyroid cancers (PTCs) between 1 and 4 cm. We aimed to examine the impact of ATA15 in a high-volume Australian endocrine surgery unit.

METHODS

A retrospective study of all patients undergoing thyroidectomy from January 2010 to December 2019.

INCLUSION CRITERIA

PTC histopathology, Bethesda V-VI, size 1-4 cm, and absence of clinical evidence of lymph node or distant metastases pre-operatively. Primary outcome was rate of HT before and after ATA15.

RESULTS

Of 5408 thyroidectomy patients, 339 (6.3%) met the inclusion criteria - 186 (54.9%) pre-ATA15 (2010-2015) and 153 (45.1%) post-ATA15 (2016-2019). The patient groups were similar; there were no significant differences between groups in age, sex, tumour size, proportion with Bethesda VI cytology, compressive symptoms, or thyrotoxicosis. Post-ATA15, there was a significant increase in HT rate from 5.4% to 19.6% (P = 0.0001). However, there was no corresponding increase in completion thyroidectomy (CT) rate (50.0% versus 27.6%, P = 0.2). The proportion managed with prophylactic central neck dissection (pCND) fell from 80.5% to 10.8% (P < 0.0001). Pre-ATA15, the only factor significantly associated with HT was Bethesda V. In contrast, post-ATA15, HT was more likely in patients with younger age, smaller tumours, and Bethesda V.

CONCLUSION

After the release of 2015 ATA guidelines, we observed a significant increase in HT rate and a significant decrease in pCND rate for low-risk PTCs in our specialised thyroid cancer unit. This reflects a growing clinician uptake of a more conservative approach as recommended by ATA15.

Current surgical treatment of intermediate risk differentiated thyroid cancer: a systematic review

Introduction: Surgical treatment of thyroid cancer has become less aggressive but for many patients, the threshold for performing total thyroidectomy (TT), as opposed to thyroid lobectomy (TL), has remained unclear. Current American Thyroid Association (ATA) guidelines encourage more individualization of treatment options, which necessitates explicit review of the pros and cons of the different options with patients.Areas covered: This review focuses on the extent of surgery for treatment of intermediate-risk differentiated thyroid cancer, restricted to relevant literature available after publication of the 2015 ATA guidelines.Expert opinion: Dynamic risk-stratification facilitates a tailored approach when deciding on the extent of surgery for thyroid cancer. Treatment with TT allows for a lower recurrence risk, a simpler follow-up regimen, and treatment with adjuvant post-operative radioactive iodine. Treatment with TL has a lower associated risk of complications and avoidance of lifelong thyroid hormone replacement but has a significant risk of requiring a completion thyroid lobectomy (CT). Overall, treatment with TL and TT have comparable survival outcomes, but TL is the more cost-effective option. Larger cancer size is correlated with worse clinical outcomes, and numerous subgroup analyses have shown poorer outcomes for cancers with a diameter that is 2-4 cm compared to 1-2 cm.

The extent of surgery for low-risk 1-4 cm papillary thyroid carcinoma: a catch-22 situation. A retrospective analysis of 497 patients based on the 2015 ATA Guidelines recommendation 35

PURPOSE

The adequate extent of surgery for 1-4 cm low-risk papillary thyroid carcinoma (PTC) is unclear. Our objective was to analyze the applicability of the 2015 ATA Guidelines recommendation 35B (R35) for the management low-risk PTC.

METHODS

This multicentre study included patients with low-risk PTC who had undergone total thyroidectomy (TT). Retrospectively we selected those who met the R35 criteria for the performance of a thyroid lobectomy (TL). The aim was to identify the proportion of low-risk PTC patients treated using TT who would have required reintervention had they had a TL in accordance with R35.

RESULTS

We identified 497 patients (400 female; 80.5%). Median tumor size (mm): 21.2 (11-40). A tumor size ≥2 cm was found in 252 (50.7%). Most of them, 320 (64.4%), were in Stage I (AJCC 7th Edition). Following R35, 286 (57.5%) would have needed TT. Thus, they would have required a second surgery had they undergone TL. The indications for reintervention would have included lymph node involvement (35%), extrathyroidal extension (22.9%), aggressive subtype (8%), or vascular invasion (22.5%). No presurgical clinical data predict TT.

CONCLUSIONS

The appropriate management of low-risk PTC is unclear. Adherence to ATA R35 could lead to a huge increase in reinterventions when a TL is performed, though the need for them would be questionable. In our sample, more than half of patients (57.5%) who may undergo a TL for a seemingly low-risk PTC would have required a second operation to satisfy international guidelines, until better preoperative diagnostic tools become available.

Additional Surgery for Occult Risk Factors After Lobectomy in Solitary Thyroid Nodules is Predicted by Cytopathology Classification and Tumor Size

OBJECTIVE

Clinical practice for differentiated thyroid cancer is moving towards lobectomy rather than total thyroidectomy in patients at low risk of recurrence. However, recurrence risk assessment depends on post-operative findings, while the surgical decision is based on preoperative factors. We determined the preoperative predictors of occult higher-risk pathology and rates of completion thyroidectomy among surgical candidates with nonbenign thyroid nodules 10 to 40 mm and no evidence of extrathyroidal extension or metastasis on preoperative evaluation.

METHODS

Thyroid surgery cases at a single institution from 2005-2015 were reviewed to identify those meeting American Thyroid Association (ATA) criteria for lobectomy. ATA-based risk stratification from postoperative surgical pathology was compared to preoperative cytopathology, ultrasound, and clinical findings.

RESULTS

Of 1,995 thyroid surgeries performed for nonbenign thyroid nodules 10 to 40 mm, 349 met ATA criteria for lobectomy. Occult high-risk features such as tall cell variant, gross extrathyroidal invasion, or vascular invasion were found in 36 cases (10.7%), while intraoperative lymphadenopathy led to surgical upstaging in 13 (3.7%). Intermediate risk features such as moderate lymphadenopathy or minimal extrathyroidal extension were present in an additional 44 cases. Occult risk features were present twice as often in Bethesda class 6 cases (35%) as in lower categories (12 to 17%). In multivariable analysis, Bethesda class and nodule size, but not age, race, sex, or ultrasound features, were significant predictors of occult higher-risk pathology.

CONCLUSION

Most solitary thyroid nodules less than 4 cm and with cytology findings including atypia of undetermined significance through suspicious for papillary thyroid cancer would be sufficiently treated by lobectomy.

ABBREVIATIONS

ATA = American Thyroid Association; CND = central neck dissection; DTC = differentiated thyroid cancer; ETE = extrathyroidal extension; FNA = fine needle aspiration; FTC/HCC = follicular thyroid carcinoma/Hurthle cell carcinoma; NIFTP = noninvasive follicular thyroid neoplasm with papillary-like nuclear features; OR = odds ratio; PTC = papillary thyroid cancer; US = ultrasound.

Thyroid Lobectomy for Low to Intermediate Risk Differentiated Thyroid Cancer

Simple Summary

Total thyroidectomy used to be recommended for all thyroid cancers. We now know that some thyroid cancers have a relatively low risk of recurrence. Today, for some of these cancers, depending on the type of tumor, its’ size and other tumor characteristics, a thyroid lobectomy (or hemithyroidectomy) can be performed without increasing the patient’s risk of cancer recurrence. Thyroid lobectomy has the advantages of having less risk of surgical complications and a less frequent need for thyroid hormone replacement therapy. This approach is not optimal for all thyroid cancers, however, and careful tumor and patient selection are necessary. This review explains the rationale and criteria for patient selection for thyroid lobectomy for selected thyroid cancers.

Abstract

Many recent publications and guidelines have promoted a “more is less” approach in terms of treatment for low to intermediate risk differentiated thyroid cancer (DTC), which comprise the vast majority of thyroid cancers: less extensive surgery, less radioactive iodine, less or no thyroid hormone suppression, and less frequent or stringent follow-up. Following this approach, thyroid lobectomy has been proposed as a means of decreasing short- and long-term postoperative morbidity while maintaining an excellent prognosis for tumors meeting specific macroscopic and microscopic criteria. This article will examine the pros and cons of thyroid lobectomy for low to intermediate risk cancers and discuss, in detail, criteria for patient selection and oncological outcomes.

Lymphovascular invasion and risk of recurrence in papillary thyroid carcinoma

BACKGROUND

Lymphovascular invasion (LVI) is an established adverse prognostic factor in many cancers, however, there are few studies assessing its significance in papillary thyroid carcinoma (PTC). We aimed to determine if LVI is an independent prognostic factor in PTC.

METHODS

We conducted a single institution retrospective analysis of 610 patients with PTC treated between 1987 and 2016. LVI was defined as the presence or absence of cancer cells in blood vessels and/or lymphatics on histopathology. Multivariate Cox regression analysis was used to evaluate the association between LVI and recurrence-free survival (RFS).

RESULTS

The study cohort included 481 (78.9%) females and 129 (21.1%) males, with a median age of 47.6 years and median follow-up of 3.4 years. LVI was present in 56 (9.2%) patients and was associated with nodal metastases (P < 0.001), extrathyroidal extension (P < 0.001), extranodal extension (P < 0.001), multifocality (P = 0.018) and microscopic positive margins (P < 0.001). On univariate analysis, LVI was associated with reduced RFS (hazard ratio (HR) 2.3; 95% confidence interval (CI) 1.3-4.3; P = 0.007). However, after adjusting for nodal stage (pN0, pN1a, pN1b) there was no association between LVI and RFS (HR 1.3; 95% CI 0.7-2.5; P = 0.398). Similar results were obtained in full multivariate models adjusting for additional prognostic factors (HR 1.2; 95% CI 0.6-2.4; P = 0.627).

CONCLUSION

LVI is strongly associated with other adverse prognostic factors in PTC, particularly the presence and extent of nodal metastases. However, after adjusting for these, LVI is not an independent predictor of recurrence.

Lymphovascular invasion of papillary thyroid carcinoma revisited in the era of active surveillance

INTRODUCTION

Lymphovascular invasion (LVI) is associated with disease recurrence and compromised survival in patients with thyroid cancer. Nonetheless, LVI is not identifiable on preoperative ultrasound or cytologic assessment. We aimed to explore the clinicopathological features associated with LVI.

PATIENTS AND METHODS

We conducted a retrospective review of our prospectively maintained database from 2009 to 2018. Multivariate analyses were performed to determine the associations between clinicopathological parameters and LVI. Generalized additive models were used to examine the nonlinear relationship between continuous variables and LVI.

RESULTS

A total of 795 patients were included in the analysis, and 174 (22%) had LVI. Patients' age (odds ratio [OR] = 0.982), tumor size (OR = 1.466), clinical lymphadenopathy (OR = 6.975), and advanced extrathyroidal extension (OR = 2.938) were independently associated with LVI. In the subset analysis of 198 patients with available genetic information, tumor size (OR = 1.599), clinical lymph node metastasis (OR = 3.657), and TERT promoter mutation (OR = 4.726) were predictive of LVI. Among 573 patients who had no clinical lymphadenopathy or advanced extrathyroidal extension, tumor size was the only predictor of LVI. Tumor size >1.5 cm had an increased risk of LVI based on the generalized additive model plot and receiver operating characteristic curve analysis.

CONCLUSION

Tumor size is positively associated with the risk of LVI in papillary thyroid cancer. To avoid delayed treatment in patients with LVI, a tumor size of 1.5 cm may be considered as the safe upper limit for active surveillance.

The American Association of Endocrine Surgeons Guidelines for the Definitive Surgical Management of Thyroid Disease in Adults

OBJECTIVE

To develop evidence-based recommendations for safe, effective, and appropriate thyroidectomy.

BACKGROUND

Surgical management of thyroid disease has evolved considerably over several decades leading to variability in rendered care. Over 100,000 thyroid operations are performed annually in the US.

METHODS

The medical literature from 1/1/1985 to 11/9/2018 was reviewed by a panel of 19 experts in thyroid disorders representing multiple disciplines. The authors used the best available evidence to construct surgical management recommendations. Levels of evidence were determined using the American College of Physicians grading system, and management recommendations were discussed to consensus. Members of the American Association of Endocrine Surgeons reviewed and commented on preliminary drafts of the content.

RESULTS

These clinical guidelines analyze the indications for thyroidectomy as well as its definitions, technique, morbidity, and outcomes. Specific topics include Pathogenesis and Epidemiology, Initial Evaluation, Imaging, Fine Needle Aspiration Biopsy Diagnosis, Molecular Testing, Indications, Extent and Outcomes of Surgery, Preoperative Care, Initial Thyroidectomy, Perioperative Tissue Diagnosis, Nodal Dissection, Concurrent Parathyroidectomy, Hyperthyroid Conditions, Goiter, Adjuncts and Approaches to Thyroidectomy, Laryngology, Familial Thyroid Cancer, Postoperative Care and Complications, Cancer Management, and Reoperation.

CONCLUSIONS

Evidence-based guidelines were created to assist clinicians in the optimal surgical management of thyroid disease.

Thyroid cancer histological subtypes based on tumor size: National perspective

BACKGROUND

Thyroid tumor size is an important prognostic factor. The aim of this study is to examine the histological subtypes and management of thyroid cancer based on tumor size (≤4 cm vs >4 cm).

METHODS

Retrospective cohort study utilizing the National Cancer Database, 2004-2014.

RESULTS

A total of 152 387 patients were included, 13 614 (8.9%) of whom had a tumor size >4 cm. Histological subtypes of tumors >4 cm were: 69.6% papillary thyroid carcinoma, 17.5% FTC, 7.9% HCC, and 2.8% medullary thyroid carcinoma (MTC). High-volume hospitals for thyroid surgery were less likely to perform two-stage thyroidectomy, particularly for tumors ≤4 cm. Low-volume hospitals had a higher risk of staged thyroidectomy for MTC ≤4 cm (19.8%) compared with high-volume hospitals (8.7%) (P < .001).

CONCLUSIONS

This study describes the prevalence of thyroid cancer subtypes. In the era of a conservative approach to differentiated thyroid carcinoma, there could be a potential increase in the risk of staged thyroidectomy.

The Identification of Intraoperative Risk Factors Can Reduce, but Not Exclude, the Need for Completion Thyroidectomy in Low-Risk Papillary Thyroid Cancer Patients

Background: The extent of initial surgical resection for low-risk papillary thyroid cancer (PTC) remains debatable. Since the 2015 American Thyroid Association (ATA) guidelines, several retrospective studies have reported that 40-60% of patients initially treated with lobectomy would require a completion thyroidectomy (CTx) due to high-risk pathological features (HRFs). These studies are limited by variable preoperative stratification and inability to quantify the value of intraoperative assessment. The study objectives were to determine whether diligent preoperative and intraoperative assessment improves the appropriateness of initial surgery for low-risk PTCs and whether varying the criteria for lobectomy reduces the need for CTx. Methods: A prospectively collected province-wide database was analyzed over a 10-year period (2008-2017) for patients who underwent a total thyroidectomy (TT) for PTC without preoperative HRFs. All patients had preoperative ultrasound and fine-needle aspirates. Unique to this database are mandatory synoptic operative fields that identify intraoperative risk factors such as positive lymph nodes and local invasion. Results: In total, 74% of patients (709/959) were deemed eligible for lobectomy. Of those eligible, 149 (21%) had intraoperative risk factors that would necessitate conversion to TT at the initial operation. A further 209 (30%) would require CTx due to HRFs on final pathology. Varying the preoperative criteria for lobectomy did not significantly affect intraoperative conversion or CTx rates. Conclusions: Although intraoperative assessment reduced the need for CTx in 21%, up to 30% of patients would still require a second operation. Altering the preoperative criteria does not influence this outcome. Patients deemed eligible for lobectomy should be informed that despite careful pre- and intraoperative assessment, there is up to a 30% risk of requiring CTx.

Integrin β4 promotes invasion and anoikis resistance of papillary thyroid carcinoma and is consistently overexpressed in lymphovascular tumor thrombus

Although the majority of papillary thyroid cancers (PTC) are indolent, a subset of PTCs behaves aggressively due to extensive invasion and distant metastasis. Integrin β4, a member of the integrin family, has been shown to enhance the progression in some malignancies; however, its role in PTC remains unclear. Here, we demonstrated that β4 overexpression was associated with extrathyroid extension, lymph node metastasis, high TNM stage, and poor overall survival based on The Cancer Genome Atlas cohort. Immunohistochemistry showed that β4 expression was significantly upregulated in the tumors with infiltrating growth pattern, as well as those with positive lymphovascular invasion. Moreover, β4 was invariably overexpressed in the lymphovascular tumor thrombi, which has not been reported before. After shRNA-induced knockdown of β4 in vitro, the migration, invasion and scratch repair ability of the tumor cells were significantly reduced. Furthermore, β4 reduction decreased anchorage-independent growth and increased anoikis. The bioinformatics analysis revealed that approximately 70 pathways were significantly dysregulated in the high β4 expression group. The MAPK pathway and propanoate metabolism were located in the network center of those pathways. Taken together, our results suggest that β4 could promote the tumor's aggressiveness by enhancing invasion and antagonizing anoikis. The upregulated expression of β4 in the tumor thrombi is intrinsically linked to its role in strengthening the anoikis resistance.

Need for Completion Thyroidectomy in Patients Undergoing Lobectomy for Indeterminate and High-Risk Nodules: Impact of Intra-Operative Findings and Final Pathology

INTRODUCTION

Current guidelines increasingly suggest the use of thyroid lobectomy for indeterminate (Bethesda 3 and 4) and high-risk (Bethesda 5 and 6) thyroid nodules; however, the clinical reality is often very different.

MATERIALS AND METHODS

The aim of this study was to determine the rate of completion thyroidectomy (CTx) for indeterminate and high-risk thyroid nodules which are pre-operatively classified as suitable for unilateral resection (lobe eligible) based on current guidelines. Seven hundred consecutive patients with thyroid nodules and FNA cytology over four years (2015-2018) were reviewed.

RESULTS

Distribution of the dominant nodules by Bethesda was: non-diagnostic 3.9%, benign 28.1%, atypia of unknown significance 19.0%, follicular neoplasm 23.6%, suspicious for malignancy 6.1% and malignancy 19.3%. Of 298 indeterminate nodules, 68.8% (205/298) had relative but independent indications for a total thyroidectomy (TTx) and the remainder were candidates for lobectomy. For these lobe eligible patients, the overall risk of ultimately needing a TTx was 19.4% (18/93), comprising 4.3% (4/93) from intra-operative findings and 15.7% (14/89) from final pathology. Similarly, of 170 high-risk nodules, 63.5% (108/170) had upfront indications for a TTx and the remaining 62 nodules were lobe eligible. Of the patients taken to the operating room for a lobectomy, 21.0% (13/62) were upgraded to a TTx intra-operatively and 26.5% (13/49) post-operatively. The lobe success rate for indeterminate nodules was 25.2% and for high-risk nodules was 21.2%. The rate of CTx, or the proportion of patients needing a second operation was 15.7% (14/89) and 26.5% (13/49), respectively.

CONCLUSIONS

In counselling a patient for surgery, the risk of needing a more radical initial procedure or second surgery needs to be accurately explained. There are three points of care that can influence operative strategy, pre-operatively by way of high-risk clinical factors, intra-operatively via anatomical findings and post-operatively in response to unrecognized pathological features. Additionally, the patient's personal value judgment and level of risk aversion should be taken into consideration.

Completion thyroidectomy: A risky undertaking?

BACKGROUND

Completion thyroidectomy (cT) is sometimes necessary after thyroid lobectomy (TL), and it remains controversial whether 2-stage thyroidectomy adds operative risk. This study compares complication rates for TL, total thyroidectomy (TT), and cT.

METHODS

Using a cohort design, we reviewed 100 consecutive cases each of TL, TT, and cT. Complications examined included reoperation for hematoma, temporary/permanent recurrent laryngeal nerve (RLN) dysfunction, and hypoparathyroidism.

RESULTS

Two patients had reoperation for hematoma, both in the TT cohort (p = 0.33). No patients in any cohort had permanent hypoparathyroidism or RLN injury, but transient RLN paresis occurred in three (3%) TL, two (2%) TT, and no (0%) cT patients (p = 0.38). Transient hypoparathyroidism occurred in 3% following TT versus 0% after cT (p = 0.12). Overall complication rate was higher after TT (7%) compared to TL (3%) and cT (0%, p = 0.02).

CONCLUSIONS

At a high-volume center, the observed complication rates were equivalently low for TL, TT, and cT.

SUMMARY

Completion thyroidectomy is occasionally needed after lobectomy, but its procedure-specific risks are not well characterized. In a cohort study at a high-volume center, operative outcomes for patients undergoing thyroid lobectomy, total thyroidectomy, and completion thyroidectomy were compared and equivalently low complication rates were observed for all 3 procedures.

Lobectomy Compared to Total Thyroidectomy for Low-Risk Papillary Thyroid Cancer: A Systematic Review

BACKGROUND

The 2015 American Thyroid Association (ATA) guidelines called for consideration of thyroid lobectomy (TL) as an acceptable surgical treatment for small and less aggressive papillary thyroid cancers (PTC) with no clinical evidence of metastasis or extrathyroidal extension. Optimal extent of surgery, however, remains controversial.

METHODS

A systematic literature review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. PUBMED, EMBASE, Scopus, and Cochrane Library databases were searched to identify studies comparing TL to total thyroidectomy (TT) for low-risk PTC. Studies were grouped according to the major outcomes in the literature: survival and the need for completion thyroidectomy (CT).

RESULTS

Overall survival for low-risk PTC patients who underwent TL was comparable to TT. Locoregional recurrence (LRR) rate following TL was less than 6% and salvaged with CT. The proportion of patients meeting the 2015 ATA guidelines selection criteria for TL who subsequently would need CT varied by study but averaged 34%. After excluding microscopic extrathyroidal extension and positive resection margin as indications for CT to facilitate radioactive iodine ablation, the estimated rate across the included studies was 11%.

CONCLUSIONS

We performed a systematic review of outcomes following TL or CT for low-risk PTC according to 2015 ATA guidelines. Initial operative approach did not have a negative impact on overall survival. There is a paucity of high-quality data on this topic across the literature. Long-term follow-up studies on oncologic and patient-centered outcomes are essential.

Are Papillary Thyroid Carcinomas That Are Candidates for Active Surveillance in Fact Classical Microcarcinomas Restricted to the Gland?

BACKGROUND

Patients with small papillary thyroid carcinomas (PTC) can currently be maintained under active surveillance (AS). The recommended criteria are the following: adult individual, tumor ≤1 cm and not adjacent to the trachea or recurrent laryngeal nerve, cytology non-suggestive of the aggressive subtype, absence of lymph node (LN) involvement and extrathyroidal extension (ETE) on ultrasonography (US), and absence of clinical distant metastases. This study aimed to evaluate the frequency of the following peri- and postoperative findings in patients who met the criteria for PTC being candidate for AS: tumor > 1 cm, aggressive subtype or vascular invasion, ETE, clinical LN metastases (cN1), and distant metastases.

METHODS

We reviewed the results of peri- and postoperative evaluation and histology of patients with a preoperative diagnosis of PTC who would currently be candidates for AS.

RESULTS

There were 124 patients (102 women) with nodules ≤1 cm (range 4-10 mm). All nodules corresponded to papillary microcarcinomas on histology and none of them were > 1 cm. Only one microcarcinoma (0.8%) was of the tall-cell subtype. Vascular invasion was found in 10 microcarcinomas (8%). None of the microcarcinomas were staged as T3b or T4, although microscopic ETE was observed in 25 tumors (20%). In 8 patients (6.4%), central LN involvement was suspected during perioperative evaluation and was confirmed by histology (cN1a). None of the patients had distant metastases (M0).

CONCLUSION

Findings that define an intermediate risk of recurrence and favor total thyroidectomy were observed in 31.5% of patients with PTC who are candidates for AS.

Dynamic risk stratification in papillary thyroid carcinoma measuring 1 to 4 cm

BACKGROUND AND OBJECTIVES

This study aimed to validate the dynamic risk stratification (DRS) system, evaluate its correlation with structural recurrence, and assess the clinicopathological risk factors associated with a nonexcellent response to initial therapy in patients with papillary thyroid cancer (PTC) measuring 1 to 4 cm.

METHODS

A total of 762 patients with classic PTC measuring 1 to 4 cm were classified into four categories based on their response to initial therapy 2 years postoperatively.

RESULTS

Structural recurrent disease occurred in 4.7%, 17.1%, 48.4%, and 83.9% of patients with excellent, indeterminate, biochemically incomplete, and structurally incomplete responses, respectively, at the time of the last follow-up. The response to initial therapy in the DRS was one of the independent risk factors for structural recurrence. The disease-free survival curves of patients with different responses showed significant differences (P < 0.001). Extensive extrathyroidal extension, lymph node (LN) metastasis, number of metastatic LNs greater than 2.0, metastatic LN ratio greater than 0.22, and extranodal extension were independent risk factors for nonexcellent response to initial therapy.

CONCLUSIONS

DRS can be a useful tool in predicting structural recurrence and guiding postoperative management and follow-up strategies in patients with PTC measuring 1 to 4 cm.

Reconsideration of tumor size threshold for total thyroidectomy in differentiated thyroid cancer

BACKGROUND

The optimal extent of surgery for differentiated thyroid cancer may not be well recognized initially. Identification of intermediate-risk features on surgical pathology may prompt the need for completion thyroidectomy if a lobectomy is performed. In this study, we examined the factors in relation to the need for completion thyroidectomy.

METHODS

We studied consecutive patients who underwent thyroidectomy for differentiated thyroid cancer from 2008 to 2017. Total thyroidectomy was indicated when tumor size >4 cm, clinical extrathyroidal extension, clinical lymph node metastasis, or distant metastasis was present. The need for completion thyroidectomy was defined as the presence of aggressive histology, extrathyroidal extension, lymphovascular invasion, or non-low-risk nodal metastasis.

RESULTS

Among 771 patients, 155 (20%) were definitely indicated for total thyroidectomy. The need for completion thyroidectomy was identified in 273 (44%) of the 616 patients initially eligible for lobectomy. The proportions of patients requiring completion thyroidectomy were 18% and 57% for microcarcinomas and tumors of 1-4 cm, respectively. Receiver operating characteristic curve analysis indicated that tumor size ≥1.1 cm had the highest accuracy of prediction. Multivariate logistic regression revealed that tumor size and BRAF V600E mutation were independent factors predicting the risk of requiring completion thyroidectomy.

CONCLUSION

A substantial portion of patients with differentiated thyroid cancer who are preoperatively eligible for lobectomy would be found to have intermediate-risk pathologic features. This should be incorporated into the shared decision making before surgery.

Individualizing Surgery in Papillary Thyroid Carcinoma Based on a Detailed Sonographic Assessment of Extrathyroidal Extension

BACKGROUND

Lobectomy may be sufficient for patients with intrathyroidal papillary thyroid carcinomas (PTC) <4 cm without nodal metastasis. Based on the 2015 American Thyroid Association guidelines, a strategy using ultrasound to identify appropriate candidates for lobectomy was implemented.

METHODS

Patients with Bethesda V or VI cytology who underwent surgery for PTC (January 2016 to May 2017) were retrospectively reviewed. Eligibility for lobectomy was based on both tumor (unilateral, intrathyroidal tumors ≤3 cm in size) and non-tumor (history of hypothyroidism, radiation exposure, etc.) characteristics. A detailed sonographic assessment of extrathyroidal extension (ETE) included surgeon-performed evaluation of thyroid capsular distortion, a long interface between tumor and thyroid capsule, irregular or indistinct tumor margins abutting the thyroid capsule, or a tracheal footprint.

RESULTS

Of 141 patients with PTC, 35 (25%) patients were candidates for lobectomy, and 105 (75%) patients were not candidates for lobectomy because of non-tumor (n = 46) or tumor (n = 59) characteristics. Of the 35 patients who were candidates for lobectomy, 27 had sonographic ETE on detailed assessment. Total thyroidectomy was performed in 23 patients, while thyroid lobectomy was performed in 12 patients. Total thyroidectomy was indicated based on final histopathology in 15 patients (ETE, aggressive histology, vascular invasion, or cervical metastasis). Histopathologic ETE was present in 13 of these 15 patients and was the only indication for total thyroidectomy in the remaining eight patients. Positive and negative predictive values for the prediction of ETE based on detailed sonographic assessment were 52% and 100%, respectively. In comparison to a strategy of routine total thyroidectomy, a detailed sonographic assessment of ETE reduced the rate of potentially avoidable total thyroidectomy from 57% to 31%.

CONCLUSIONS

Patients with PTC who are potential candidates for lobectomy often require total thyroidectomy based on microscopic ETE detected on surgical pathology. A detailed sonographic assessment of ETE can reliably rule out microscopic ETE, reducing the rate of potentially avoidable total thyroidectomy.

Correct extent of thyroidectomy is poorly predicted preoperatively by the guidelines of the American Thyroid Association for low and intermediate risk thyroid cancers

BACKGROUND

Recent guidelines from the American Thyroid Association recommend thyroid lobectomy for intrathyroidal differentiated thyroid cancers <4 cm. Our aim was to examine histology from patients with cytologic results that were positive or suspicious for malignancy to assess the extent of initial thyroidectomy based on criteria from the 2015 American Thyroid Association guidelines.

METHODS

We studied consecutive patients who had either a positive or suspicious for malignancy cytologic diagnosis and under prior American Thyroid Association guidelines underwent initial total thyroidectomy ± lymphadenectomy.

RESULTS

Among 447 patients, high-risk features necessitating total thyroidectomy were present in 19% (72/380) of positive and 15% (10/67) of suspicious for malignancy patients (P = .5). Intermediate-risk features on histology were identified postoperatively in 46% (175/380) with positive and 15% (18/67) with suspicious for malignancy fine-needle aspiration results. In multivariable analysis, preoperative factors associated with intermediate-risk disease included age ≥45 years, women, larger tumor size, positive fine-needle aspiration cytology, and BRAF V600E or RET/PTC positivity.

CONCLUSION

When patients are considered for lobectomy under the 2015 American Thyroid Association guidelines, ~ 60% with positive and 30% with suspicious for malignancy cytology would need completion thyroidectomy based on intermediate-risk disease. The cost and risk implications of the new American Thyroid Association strategy were substantial and better tools are needed to improve preoperative risk stratification.