Recurrence Risk Evaluation in Patients with Papillary Thyroid Carcinoma: Multicenter Machine Learning Evaluation of Lymph Node Variables.

Background: Lymph node (LN)-related risk factors have been updated to predict long-term outcomes in patients with papillary thyroid carcinoma (PTC). However, those factors' analytic appropriateness and general applicability must be validated. This study aimed to assess LN-related risk factors, and suggest new LN-related risk categories. Methods: This multicenter observational cohort study included 1232 patients with PTC with N1 disease treated with a total thyroidectomy and neck dissection followed by radioactive iodine remnant ablation. Results: The median follow-up duration was 117 months. In the follow-up period, structural recurrence occurred in 225 patients (18.3%). Among LN-related variables, the presence of extranodal extension (p < 0.001), the maximal diameter of metastatic LN foci (p = 0.029), the number of retrieved LNs (p = 0.003), the number of metastatic LNs (p = 0.003), and the metastatic LN ratio (p < 0.001) were independent risk factors for structural recurrence. Since these factors showed a nonlinear association with the hazard ratio of recurrence-free survival (RFS) rates, we calculated their optimal cutoff values using the K-means clustering algorithm, selecting 0.2 cm and 1.1 cm for the maximal diameter of metastatic LN foci, 4 and 13 for the number of metastatic LN, and 0.28 and 0.58 for the metastatic LN ratio. The RFS curves of each subgroup classified by these newly determined cutoff values showed significant differences (p < 0.001). Each LN risk group also showed significantly different RFS rates from the others (p < 0.001). Conclusions: In PTC patients with an N1 classification, our novel LN-related risk estimates may help predict long-term outcomes and design postoperative management and follow-up strategies. After further validation studies based on independent datasets, these risk categories might be considered when redefining risk stratification or staging systems.

Thyroid Cancer in Patients with Metabolic Syndrome or Its Components: A Nationwide Population-Based Cohort Study.

The rapidly increasing coincidence of thyroid cancer and metabolic syndrome (MS) in recent decades suggests an association between the two disorders. To investigate this association, we conducted a nationwide study of a large-scale patient cohort. Between 2009 and 2011, data were collected by the Korean National Health Insurance Service for 4,658,473 persons aged 40−70 years without thyroid cancer. During the six-year follow-up period, participants were monitored for the development of thyroid cancer. The relative risks and incidences of thyroid cancer were calculated using multivariate Cox proportional hazards regression analyses after adjusting for age and body mass index. The risk of thyroid cancer was significantly elevated in men and women with MS or MS components, except for hyperglycaemia (p = 0.723) or hypertriglyceridemia (p = 0.211) in men. The incidence of thyroid cancer per 10,000 person-years in individuals with MS was significantly higher in men (6.2, p < 0.001) and women (21.3, p < 0.001) compared to those without MS. Additionally, the risk of thyroid cancer increased significantly with an increasing number of MS components even in individuals with only one or two MS components. MS and its components were significantly associated with increased risk of developing thyroid cancer.

Restratification of Patients with Intermediate-Risk Papillary Thyroid Carcinoma.

BACKGROUND: Long-term management and follow-up strategies in patients with intermediate-risk papillary thyroid carcinoma (PTC) according to the American Thyroid Association (ATA) are still controversial due to the paucity of data on unique risk factors or a risk stratification system predictive of long-term outcomes. PATIENTS AND METHODS: This study included 649 patients with PTC who underwent an initial surgical treatment. Retrospectively enrolled patients were categorized according to the ATA risk stratification system. Intermediate-risk patients were further categorized into subgroups by the number of ATA intermediate risk factors. The recurrence-free survival (RFS) rates of these subgroups were compared with those of low- and high-risk patient groups. Additionally, the patients were classified according to their response to the initial therapy using the dynamic risk stratification (DRS) system, and the percentages of patients in each category were compared among the subgroups. RESULTS: The median follow-up period was 102 months. Structural recurrence occurred in 9.2% of all enrolled patients (60/649) and in 13.0% of intermediate-risk patients (40/308). Patients with two or more current intermediate risk factors had a poorer RFS than patients with only one risk factor (p < 0.001) and showed a comparable RFS to high-risk patients (p > 0.050). The percentages of patients with an excellent response category for DRS significantly decreased with an increase in the number of intermediate risk factors. CONCLUSION: Subclassification according to the number of intermediate risk factors may be useful to better predict the RFS and the response to initial therapy in patients with intermediate-risk PTC.

Optimal cutoff values of primary tumour size to better predict long-term outcomes in patients with papillary thyroid carcinoma undergoing total thyroidectomy: A preliminary study using restricted cubic spline analysis.

OBJECTIVE: Primary tumour size (PTS) is known to be a significant prognostic factor in patients with papillary thyroid carcinoma (PTC) undergoing thyroidectomy. Although cutoff values of 2 and 4 cm are widely used in surgical extent decision and long-term outcomes predictions, the effectiveness of arbitrary cutoff values in stratifying patients for target outcomes is questionable. This study aimed to determine new optimal cutoffs of PTS. DESIGN, PATIENT AND MEASUREMENTS: Patients (n = 529) with PTC who underwent total thyroidectomy were retrospectively reviewed. After risk factor analysis for structural recurrence, the optimal cutoffs of PTS were automatically calculated using restricted cubic spline analysis and X-tile software. Subgroups were classified based on the newly determined cutoff values. Both the recurrence-free survival (RFS) and the proportion of patients in each response-to-therapy category, using the dynamic risk stratification system (DRS), were compared between the subgroups. RESULTS: PTS was confirmed as an independent risk factor for structural recurrence. The optimal cutoff values were calculated as 1.4 and 3.0 cm. The subgroups stratified using these newly determined cutoffs showed significantly different RFS and DRS based on the response to initial therapy, but the subgroups classified using the cutoffs of 2 and 4 cm did not. CONCLUSIONS: The newly determined cutoff values of PTS may be useful in better stratifying patients with PTC undergoing thyroidectomy for target outcomes and can be considered as a new definition in staging and risk stratification systems.

Comparison of the abilities of staging and risk stratification systems to predict the long-term structural recurrence in patients with differentiated thyroid carcinoma after total thyroidectomy and radioactive iodine remnant ablation.

BACKGROUND: In patients with differentiated thyroid carcinoma (DTC), various staging and risk stratification systems have been applied to estimate long-term recurrence, which is a major issue during the postoperative follow-up period. However, the efficacy of these systems remains unclear in this context. METHODS: The present historical cohort study included 510 patients with DTC who underwent a total thyroidectomy followed by radioactive iodine (RAI) remnant ablation. Enrolled patients were categorized according to the 8th edition of American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) Tumor Node Metastasis (TNM) staging system, the 2015 American Thyroid Association (ATA) initial risk stratification system, and the dynamic risk stratification (DRS) system. The ability of each system to predict long-term structural recurrence was compared using proportion of variance explained (PVE) by logistic regression models. RESULTS: The median follow-up period was 108 months. Structural recurrence occurred in 7.6% of the patients (n=39/510). Disease-free survival (DFS) curves of the patients within each category in the TNM staging system, the ATA initial risk stratification system, and the DRS system were significantly different (P<0.001). The PVE of the DRS system (20.7%) was higher than those of the TNM staging system and the ATA initial risk estimates. CONCLUSIONS: The DRS system may effectively predict long-term structural recurrence and guide long-term management and follow-up strategies in patients with DTC undergoing total thyroidectomy and RAI remnant ablation.

Optimal Timing of Initiating Dynamic Risk Stratification During the Early Postoperative Period in Patients with Differentiated Thyroid Carcinoma After Thyroidectomy and Radioactive Iodine Remnant Ablation.

BACKGROUND: This study investigated the optimal timing to initiate assessment of the response to initial therapy during the early postoperative period in patients with differentiated thyroid carcinoma (DTC) using dynamic risk stratification (DRS). METHODS: This historical cohort study included 510 patients with DTC who underwent a total thyroidectomy followed by radioactive iodine (RAI) remnant ablation. DRS for these patients was categorized into subgroups according to the time into the follow-up period at which the response to initial therapy was assessed. The ability of each DRS subgroup to predict the long-term structural recurrence of cancer was compared using the proportion of variance explained (PVE) from logistic regression models. RESULTS: The median follow-up period was 108 months. Structural recurrence occurred in 7.6% of patients (n = 39/510). The PVE for long-term structural recurrence was higher among DRS subgroups (28.8-34.19%) compared with the American Joint Committee on Cancer/Union for International Cancer Control tumor-node-metastasis staging system (both the 7th and 8th editions; 4.01% and 6.13%, respectively) and the American Thyroid Association initial risk estimate (4.59%). Among the DRS subgroups, DRS assessed between 2 and 3 years after the initial surgery was associated with the highest PVE (34.19%). CONCLUSIONS: The first assessment of DRS optimally predicts long-term structural recurrence in patients with DTC who underwent a total thyroidectomy and subsequent RAI remnant ablation at that 2- to 3-year postoperative period.

Lobectomy in patients with differentiated thyroid cancer: indications and follow-up.

The extent of thyroid surgery for patients with low- and intermediate-risk differentiated thyroid carcinoma (DTC), with a primary tumour <4 cm and no extrathyroidal extension (ETE) or lymph node (LN) metastases, has shifted in a more conservative direction. However, clinicopathological risk factors, including microscopic ETE, aggressive histology, vascular invasion in papillary thyroid carcinoma (PTC) and intermediate volume of LN metastases, can only be identified after completing thyroid lobectomy. It is controversial whether patients with these risk factors should immediately undergo complete thyroidectomy and/or radioactive iodine remnant ablation or should be monitored without further treatments. Data are conflicting about the prognostic impact of these risk factors on clinical DTC outcomes. Notably, the recurrence rate in patients who underwent thyroid lobectomy is low and the few recurrences that develop during long-term follow-up can readily be detected by neck ultrasonography and treated by salvage surgery with no impact on survival. These findings suggest that a more conservative approach may be a preferred management strategy over immediate completion surgery, despite a slightly higher risk of structural recurrence. Regarding follow-up of post-lobectomy DTC patients, it is reasonable that an initial risk stratification system based on clinicohistological findings be used to guide the short-term follow-up prior to evaluating the response to initial therapy and that the dynamic risk stratification system based on the response to initial therapy be used to guide long-term follow-up.

The definition of lymph node micrometastases in pathologic N1a papillary thyroid carcinoma should be revised.

BACKGROUND: The aim of this study was to identify the risk factors for structural recurrence with a focus on lymph node-related factors and to determine the optimal cutoff size of lymph node micrometastases in patients with pathologic N1a classical papillary thyroid carcinoma. METHODS: We included patients who underwent total thyroidectomy with central compartment lymph node dissection for classic papillary thyroid carcinoma with pathologic N1a classification. RESULTS: A total of 398 patients were followed up for a median of 131 months. Structural recurrence occurred in 17.3% of patients (69/398). The multivariate analysis reported the following independent risk factors for structural recurrence: tumor size >1.95 cm, bilaterality, lymphatic and/or vascular invasion, a maximum diameter of the metastatic lymph node focus >3.5 mm, distribution of metastatic lymph node foci size >3.0 mm, and ≥4 metastatic lymph nodes. CONCLUSION: The newly proposed cutoff of 3.5 mm for a definition of lymph node micrometastasis in pathologic N1a papillary thyroid carcinoma patients can reclassify the risk estimates of structural recurrence, thus modifying postoperative management plans and follow-up strategies.

Comparison of short-term oncologic outcome of robotic thyroid surgery using dynamic risk stratification: A propensity score-matched comparison study.

BACKGROUND: The long-term oncologic outcome of robotic surgery for thyroid cancer is not well established. The aim of this study was to predict the long-term oncologic outcome of robotic surgery by using dynamic risk stratification in classic papillary thyroid carcinoma. METHODS: A total of 444 propensity score-matched pairs of patients with papillary thyroid carcinoma treated with robotic surgery and conventional open surgery were classified into 4 response-to-therapy categories. The results were compared between the robotic surgery and open surgery groups. RESULTS: The median follow-up duration was 60 months. After propensity score matching, the robotic surgery group showed less extensive thyroid surgery and lymph node dissection and a higher proportion of patients who underwent radioactive iodine remnant ablation than the open surgery group; however, the dynamic risk stratification did not differ between the 2 groups (P = .086). CONCLUSION: The long-term oncologic outcome of robotic surgery is expected to be comparable with that of open surgery based on the dynamic risk stratification.

The prognostic value of serum thyroid-stimulating hormone level post-lobectomy in low- and intermediate-risk papillary thyroid carcinoma.

BACKGROUND: This study was undertaken to determine the optimal thyroid-stimulating hormone (TSH) value associated with structural recurrence in patients with low-risk or intermediate-risk papillary thyroid carcinoma (PTC) who underwent thyroid lobectomy. METHODS: Patients with PTC (n = 1047) who received thyroid lobectomy and central compartment node dissection were included in the study. RESULTS: Structural recurrence occurred in 42 of the patients (4.0%), and no patient died of PTC. Multivariate analysis showed a primary tumor size (with a cut-off of 0.85 cm) and serum TSH level measured 1 year after the initial surgery (cut-off 1.85 mU/L) independently predicted structural recurrence. CONCLUSIONS: TSH levels during the early postoperative period need to be monitored and maintained in the lower normal range even in patients with low- or intermediate-risk PTC undergoing thyroid lobectomy.

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.

Dynamic risk stratification system in post-lobectomy low-risk and intermediate-risk papillary thyroid carcinoma patients.

OBJECTIVE: The dynamic risk stratification (DRS) and its current definition of each response-to-therapy category in post-lobectomy papillary thyroid carcinoma (PTC) patients have not been well studied. This study aimed to validate the DRS system and to investigate useful thyroglobulin (Tg) or anti-Tg antibody (Ab)-related parameters in defining each response-to-therapy category. DESIGN: Retrospective observational study. PATIENTS: This historical cohort study included 619 patients with PTC treated by thyroid lobectomy. MEASUREMENTS: All enrolled participants were stratified according to the American Thyroid Association (ATA) initial risk stratification system and DRS system, respectively. The association between these stratifications and structural recurrence was evaluated. RESULTS: The median follow-up period was 103 months. Structural recurrence occurred in 1.6% of the patients with excellent response, 3.8% of those with indeterminate response, 2.9% of those with biochemical incomplete response, and all patients with structural incomplete response. Five (1.5%) of the low-risk patients and 14 (5.0%) of the intermediate-risk patients had structural recurrence. The disease-free survival curves showed significant differences according to the DRS (P < .001) and ATA initial risk stratification (P = .012), respectively. The proportion of variance explained the DRS system and ATA risk stratification system for structural recurrence was 32.4% and 29.4%, respectively. A thyroid-stimulating hormone (TSH) level >2.75 µU/mL at 1 year after the initial operation (P < .001) was the only valuable risk factor for structural recurrence identified in this study. CONCLUSION: The long-term postoperative management of PTC patients treated with thyroid lobectomy could be guided based on the DRS.

Factors related to improved clinical outcomes associated with adrenalectomy for metachronous adrenal metastases from solid primary carcinomas.

BACKGROUND: Surgery for metachronous adrenal metastases from solid primary carcinoma has increased with the development of technical skills. Here we analyzed the postoperative clinical outcomes of patients who underwent adrenalectomy for metachronous adrenal metastases from solid primary carcinomas. METHODS: Patients who underwent adrenalectomy for metachronous adrenal metastases after initial treatment of primary carcinoma at Asan Medical Center from 2000 to 2010 were included. Clinicopathological parameters were analyzed to evaluate prognostic outcomes. RESULTS: A total of 30 patients with 19 hepatocellular carcinomas and 11 lung carcinomas were included. The mean age was 54.3 years. The mean time until adrenalectomy was 23 months. The size of the metastatic adrenal tumor and the disease status of the primary carcinoma at the time of adrenalectomy were associated with second recurrence after adrenalectomy (P < 0.05). There was no significant difference in disease-specific recurrence-free survival between patients who underwent open adrenalectomy and laparoscopic adrenalectomy (P = 0.646). CONCLUSIONS: Surgical treatment should be recommended for metachronous adrenal metastases in patients with no evidence of primary carcinoma and/or in those having metastatic adrenal tumors ≤4.4 cm. This approach may increase the recurrence-free interval related to second recurrence. Further, laparoscopic adrenalectomy appears sufficient for the treatment of such patients.

Postsurgical Outcomes and Surgical Completeness of Robotic Thyroid Surgery: A Single Surgeon's Experience on 700 Cases.

BACKGROUND: Advanced technology and understanding of robotic surgical system have rendered robotic thyroid surgery more expanding. The aim of this study was to identify the periodic changes in postsurgical outcomes of robotic thyroid surgery performed by a single surgeon. METHODS: We conducted a retrospective review of 700 robotic thyroid surgery cases using gasless trans-axillary approach. RESULTS: All patients underwent successful operations without conversion to open surgery, and were mostly younger than 45 years, female, less-extended thyroid surgery and lymph node dissection, and thyroid cancer. The median follow-up period was 67 months (12-99 months). Regarding technical outcomes, the operation time declined steeply after 100 consecutive cases, and reached 120.0-132.7 minutes for thyroid lobectomy and 162.9-174.1 minutes for total thyroidectomy (TT). The most common complication was transient hypoparathyroidism (43.7%), whose incidence decreased steeply to a range of 9.1% to 25.0% after 300 consecutive cases. Regarding surgical completeness for thyroid cancer, an average of seven lymph nodes was retrieved through central compartment node dissection without fluctuation over time. The proportion of the patients with serum stimulated thyroglobulin levels <10 ng/mL at the time of radioactive iodine remnant ablation after TT and <1 ng/mL 6-12 months after the first remnant ablation ranged between 86.4%-100% and 66.7%-100%, respectively, without significant fluctuation. CONCLUSION: For properly selected patients, robotic thyroid surgery is useful surgical option with reliable technical outcome and surgical completeness and cosmetic benefit.

Dynamic Risk Stratification in Stage I Papillary Thyroid Cancer Patients Younger Than 45 Years of Age.

BACKGROUND: This study validated the dynamic risk stratification (DRS) system with regard to its association with structural recurrence and risk factors associated with non-excellent responses in patients <45 years with stage I classical papillary thyroid cancer (PTC). METHODS: This historical cohort study included 598 patients with stage I classical PTC <45 years of age treated with total thyroidectomy followed by radioactive iodine remnant ablation (n = 440), total thyroidectomy without radioactive iodine remnant ablation (n = 23), and thyroid lobectomy alone (n = 135). RESULTS: The median follow-up period was 123 months. Structural recurrence occurred in 4.2% (n = 18/432) of the patients with an excellent response, 17.1% (18/105) of patients with an indeterminate response, 44.7% (17/38) of patients with a biochemically incomplete response, and 82.6% (19/23) of patients with a structurally incomplete response (p < 0.001) during the follow-up. The disease-free survival curves of each response showed significant differences (p < 0.001). Extensive extrathyroidal extension and extranodal extension were the independent risk factors associated with non-excellent response (p < 0.05). CONCLUSIONS: DRS may reduce unnecessary additional treatments by reclassifying initial risk estimates of structural recurrence. Furthermore, applying the risk factors associated with non-excellent response to initial therapy may be a more useful and viable surrogate of the risk for structural recurrence in stage I PTC patients <45 years of age.

Preoperative clinicopathological characteristics of patients with solitary encapsulated follicular variants of papillary thyroid carcinomas.

BACKGROUND AND OBJECTIVES: Clinical outcomes in patients with the follicular variant of papillary thyroid carcinoma (FVPTC) tend to vary according to the pathological subtypes. We aimed to evaluate the clinicopathological characteristics including preoperative radiological and cytopathological diagnoses in patients with solitary encapsulated FVPTCs (EFVPTCs) to prove the preoperative assessment dilemma. METHODS: Patients with solitary FVPTCs who underwent thyroid surgery were included. RESULTS: Of 271 patients, 194 patients (72%) had EFVPTCs, whereas 77 patients (28%) had infiltrative FVPTCs (IFVPTCs). EFVPTCs had larger tumor sizes (P < 0.001) and lower frequencies of extrathyroidal extension (P < 0.001) and cervical lymph node (LN) metastasis (P < 0.001) than IFVPTCs. There were significant differences in ultrasonography (US) findings, preoperative cytopathological diagnosis, and the prevalence of BRAF mutations between EFVPTCs and IFVPTCs. Invasive EFVPTCs were diagnosed in 89 patients (33%) and non-invasive EFVPTCs in 105 patients (39%). Non-invasive subtype had smaller tumor sizes (P = 0.001) and lower frequencies of vascular invasion (P = 0.04) and cervical LN metastasis (P = 0.02). There were no significant differences in preoperative US findings and cytopathological diagnoses between invasive and non-invasive EFVPTCs. CONCLUSIONS: Clinicopathological characteristics of EFVPTCs, including preoperative US findings, are different from those of IFVPTCs. However, preoperative radiological and cytopathological findings could not distinguish non-invasive and invasive EFVPTCs.

Lack of Efficacy of Radioiodine Remnant Ablation for Papillary Thyroid Microcarcinoma: Verification Using Inverse Probability of Treatment Weighting.

BACKGROUND: Most of the increase in thyroid cancer in recent decades has been due to papillary thyroid microcarcinoma (PTMC). We evaluated the efficacy of radioiodine remnant ablation (RRA) in patients with PTMC. METHODS: This historical cohort study included 1932 PTMC patients without lateral cervical lymph node (LN) or distant metastasis who underwent total thyroidectomy (TT) during the median 8.3 years of follow-up. The clinical outcomes of patients with or without RRA were compared using weighted logistic regression models with the inverse probability of treatment weighting (IPTW) method and considering risk factors, including age, sex, primary tumor size, extrathyroidal extension, multifocality, and central cervical LN metastasis. RESULTS: The median primary tumor size of the RRA group was significantly larger than that of the no-RRA group (0.7 vs. 0.5 cm, P < 0.001). There were significantly more patients with multifocality, extrathyroidal extension, and cervical LN metastasis in the RRA group compared with the no-RRA group. There was no significant difference in recurrence-free survival between the two groups (P = 0.11). Cox proportional-hazard analysis with IPTW by adjusting for clinicopathological risk factors demonstrated no significant difference in recurrence of PTMC according to RRA treatment (hazard ratio [HR] 2.02; 95% confidence interval [CI] 0.65-6.25; P = 0.2). CONCLUSIONS: RRA had no therapeutic effect on the clinical outcomes of patients with PTMC who underwent TT. Surgical treatment without RRA could be applicable for patients with PTMC if there is no evidence of lateral cervical LN metastasis or distant metastasis.

Is Male Gender a Prognostic Factor for Papillary Thyroid Microcarcinoma?

BACKGROUND: Male gender is a prognostic factor of poor outcome in papillary thyroid carcinoma (PTC). We investigated the prognostic role of male gender in papillary thyroid microcarcinoma (PTMC). METHODS: We included 2930 patients who underwent surgery at Asan Medical Center for PTC. Clinicopathologic characteristics from the patients' medical records were compared for male and female PTC patients. Independent prognostic factors for recurrence in PTC and PTMC were evaluated after propensity score matching analysis. The median follow-up period was 82 months. RESULTS: Recurrence and death were more common in male patients with PTC than in female patients with PTC (12.6 vs. 9.6%, p = 0.03 and 2.2 vs. 0.6%, p < 0.001, respectively). However, there was no difference in disease-free survival between male and female PTMC patients (p = 0.57). Multivariate analysis after propensity score matching revealed that male gender is not an independent prognostic factor of recurrence in PTMC (hazard ratio [HR] 1.5, 95% confidence interval 0.75-5.33, p = 0.17), but that it is an independent prognostic factor in PTC >1 cm (HR = 3.06, 95% confidence interval 1.34-6.98, p = 0.008). CONCLUSIONS: Male gender is an independent prognostic factor for recurrence in PTC >1 cm, but it is not a prognostic factor in PTMC.

A comparison of lobectomy and total thyroidectomy in patients with papillary thyroid microcarcinoma: a retrospective individual risk factor-matched cohort study.

OBJECTIVE: Papillary thyroid microcarcinoma (PTMC) accounts for most of the increase in thyroid cancer in recent decades. We compared clinical outcomes and surgical complications of lobectomy and total thyroidectomy (TT) in PTMC patients. DESIGN AND METHODS: In this retrospective individual risk factor-matched cohort study, 2031 patients with PTMC were initially included. Patients who underwent lobectomy or TT were one-to-one matched according to individual risk factors, including age, sex, primary tumor size, extrathyroidal extension, multifocality and cervical lymph node (LN) metastasis. RESULTS: In total, 688 patients were assigned to each group. During the median 8.5 years of follow-up, 26 patients (3.8%) in the lobectomy group and 11 patients (1.6%) in the TT group had recurrences. The relative risk of recurrence was significantly less in the TT than that in the lobectomy group (hazard ratio (HR) 0.41; 95% confidence interval (CI) 0.21-0.81; P = 0.01). Most recurrences (84.6%) in the lobectomy group occurred in the contralateral lobe, and all patients were disease-free after completion of thyroidectomy. There were no significant differences in recurrence-free survival between the two groups after exclusion of contralateral lobe recurrences (HR, 2.75; 95% CI, 0.08-8.79; P = 0.08). There were significantly more patients with transient and permanent hypoparathyroidism in the TT than that in the lobectomy group (P < 0.001). CONCLUSIONS: Lobectomy could be appropriate for most patients with PTMC when there is no evidence of extrathyroidal disease in the preoperative work-up. Preoperative and postoperative imaging studies are important for patients who undergo lobectomy for PTMC, because most recurrences are in the contralateral lobe.