Prognosis of Patients with Cutaneous Angiosarcoma After Surgical Resection with Curative Intent: Is There a Difference Between the Subtypes?

BACKGROUND: The etiology of cutaneous angiosarcoma (cAS) may be idiopathic (I-cAS), or arise secondary to radiotherapy (RT-cAS), in chronic lymphedema (ST-cAS), or related to UV exposure (UV-cAS). The aim of this study was to evaluate oncological outcomes of different cAS subtypes. PATIENTS AND METHODS: Non-metastatic cAS patients, treated with surgery for primary disease with curative intent, were retrospectively analyzed for oncological outcome, including local recurrence (LR), distant metastases (DM), and overall survival (OS). RESULTS: A total of 234 patients were identified; 60 I-cAS, 122 RT-cAS, 9 ST-cAS, and 43 UV-cAS. The majority was female (78%), the median age was 66 years (IQR 57-76 years), the median tumor size was 4.4 cm (IQR 2.5-7.0 cm), and most common site of disease was the breast (59%). Recurrence was identified in 66% (44% LR and/or 41% DM), with a median follow up of 26.5 months (IQR 12-60 months). The 5-year OS was estimated at 50%, LRFS at 47%, and DMFS at 50%. There was no significant difference in LR, DM, or OS between the subtypes. Age < 65 years and administration of radiotherapy (RT) were significantly associated with lower LR rates (HR 0.560, 95% CI 0.3373-0.840, p = 0.005 and HR 0.421, 95% CI 0.225-0.790, p = 0.007, respectively), however no prognostic factors were identified for development of DM. Development of DM, but not LR (p = 0.052), was significantly associated with decreased OS (HR 6.486, 95% CI 2.939-14.318 p < 0.001). CONCLUSION: We found no significant difference in oncological outcome between the different cAS subtypes. OS remains relatively poor, and RT is associated with lower LR rates.

MET-receptor targeted fluorescent imaging and spectroscopy to detect multifocal papillary thyroid cancer.

PURPOSE: Multifocal disease in PTC is associated with an increased recurrence rate. Multifocal disease (MD) is underdiagnosed with the current gold standard of pre-operative ultrasound staging. Here, we evaluate the use of EMI-137 targeted molecular fluorescence-guided imaging (MFGI) and spectroscopy as a tool for the intra-operative detection of uni- and multifocal papillary thyroid cancer (PTC) aiming to improve disease staging and treatment selection. METHODS: A phase-1 study (NCT03470259) with EMI-137 was conducted to evaluate the possibility of detecting PTC using MFGI and quantitative fiber-optic spectroscopy. RESULTS: Fourteen patients underwent hemi- or total thyroidectomy (TTX) after administration of 0.09 mg/kg (n = 1), 0.13 mg/kg (n = 8), or 0.18 mg/kg (n = 5) EMI-137. Both MFGI and spectroscopy could differentiate PTC from healthy thyroid tissue after administration of EMI-137, which binds selectively to MET in PTC. 0.13 mg/kg was the lowest dosage EMI-137 that allowed for differentiation between PTC and healthy thyroid tissue. The smallest PTC focus detected by MFGI was 1.4 mm. MFGI restaged 80% of patients from unifocal to multifocal PTC compared to ultrasound. CONCLUSION: EMI-137-guided MFGI and spectroscopy can be used to detect multifocal PTC. This may improve disease staging and treatment selection between hemi- and total thyroidectomy by better differentiation between unifocal and multifocal disease. TRIAL REGISTRATION: NCT03470259.

Intraoperative MET-receptor targeted fluorescent imaging and spectroscopy for lymph node detection in papillary thyroid cancer: novel diagnostic tools for more selective central lymph node compartment dissection.

PURPOSE: Patients undergoing prophylactic central compartment dissection (PCLND) for papillary thyroid cancer (PTC) are often overtreated. This study aimed to determine if molecular fluorescence-guided imaging (MFGI) and spectroscopy can be useful for detecting PTC nodal metastases (NM) and to identify negative central compartments intraoperatively. METHODS: We used a data-driven prioritization strategy based on transcriptomic profiles of 97 primary PTCs and 80 normal thyroid tissues (NTT) to identify tumor-specific antigens for a clinically available near-infrared fluorescent tracer. Protein expression of the top prioritized antigen was immunohistochemically validated with a tissue microarray containing primary PTC (n = 741) and NTT (n = 108). Staining intensity was correlated with 10-year locoregional recurrence-free survival (LRFS). A phase 1 study (NCT03470259) with EMI-137, targeting MET, was conducted to evaluate safety, optimal dosage for detecting PTC NM with MFGI, feasibility of NM detection with quantitative fiber-optic spectroscopy, and selective binding of EMI-137 for MET. RESULTS: MET was selected as the most promising antigen. A worse LRFS was observed in patients with positive versus negative MET staining (81.9% versus 93.2%; p = 0.02). In 19 patients, no adverse events related to EMI-137 occurred. 0.13 mg/kg EMI-137 was selected as optimal dosage for differentiating NM from normal lymph nodes using MFGI (p < 0.0001) and spectroscopy (p < 0.0001). MFGI identified 5/19 levels (26.3%) without NM. EMI-137 binds selectively to MET. CONCLUSION: MET is overexpressed in PTC and associated with increased locoregional recurrence rates. Perioperative administration of EMI-137 is safe and facilitates NM detection using MFGI and spectroscopy, potentially reducing the number of negative PCLNDs with more than 25%. CLINICAL TRIAL REGISTRATION: NCT03470259.

Radiofrequency Ablation for Benign Symptomatic Thyroid Nodules in the Netherlands: Successful Introduction of a Minimally Invasive Treatment Option Improving Quality of Life.

PURPOSE: To determine whether adoption of radiofrequency (RF) ablation in patients with symptomatic benign thyroid nodules (SBTNs) in a Dutch regional thyroid network resulted in clinical success and improvement in health-related and thyroid-related quality of life (QoL). MATERIALS AND METHODS: The eligibility criteria for RF ablation were as follows: (a) nodule size between 2.0 and 5.0 cm, (b) solid component >20%; (c) benign cytology in 2 separate cytological assessments, and (d) symptoms unequivocally related to mechanical compression. The primary end point of this study was volume reduction 1 year after ablation. The secondary outcomes were health-related and thyroid-related QoL, measured using the short form health survey questionnaire (SF-36) and thyroid-specific patient-reported outcome questionnaire (ThyPRO-39), respectively, as well as adverse event rates. RESULTS: A total of 72 SBTNs in 67 patients were included. Median age was 50.0 (interquartile range, 41.0-56.0) years, and 91.0% were women. The median volume reduction at 6 weeks, 6 months, 1 year, 2 years, and 3 years was 51.0%, 63.9%, 65.2%, 81.3%, and 90.3%, respectively. The patients showed a significant improvement on the SF-36 physical component scale and ThyPRO-39 overall QoL-impact scale. An absolute improvement was seen in goiter and cosmetic complaints, determined using ThyPRO-39. The overall adverse event rate was 9.0%, of which 4.5% were considered major. CONCLUSIONS: RF ablation is an effective treatment option for SBTNs, with a significant volume reduction and improvement in health-related and thyroid-related QoL.

Thyroglobulin and thyroglobulin antibodies: assay-dependent management consequences in patients with differentiated thyroid carcinoma.

OBJECTIVES: International guidelines recommend fixed cut-off values for thyroglobulin (Tg). These cut-offs do not take potential assay differences into account. This study aimed to evaluate if different assays for Tg and Tg antibodies (TgAb) affect management guidance for differentiated thyroid cancer (DTC) patients. METHODS: In 793 samples derived from 413 patients with DTC, Tg and TgAb were simultaneously measured with two immunometric assays: Immulite 2000XPi and Kryptor compact plus. In addition, a qualitative measurement for TgAb interference (recovery test) was performed on the Kryptor compact plus platform. The extent to which different assays lead to different classifications of response to therapy was evaluated when applying the current cut-offs for Tg. RESULTS: Mean Tg concentrations were 37.4% lower with Kryptor as compared with Immulite. Applying guideline based cut-off values for Tg, 33 (4.7%) samples had a Tg-on concentration ≥1.0 µg/L with Immulite and <1.0 µg/L with Kryptor. Of the samples tested as TgAb+ with at least one assay (n=125), 68 (54.4%) samples showed discrepancy in TgAb status. Differences between Immulite and Kryptor measurements resulted in a change in the response to therapy classification in 94 (12.0%) measurements derived from 67 (16.2%) individual patients. CONCLUSIONS: A substantial portion of DTC patients were classified differently dependent on which Tg and TgAb assays are used, when applying the cut-off values as defined in clinical guidelines. Such differences can significantly affect clinical management. In the context of large between-method variation, the recommended Tg cut-offs in guidelines should be used with wisdom rather than as fixed cut-offs.

A Novel and Generic Workflow of Indocyanine Green Perfusion Assessment Integrating Standardization and Quantification Toward Clinical Implementation.

OBJECTIVE: This study aims to generate a reproducible and generalizable Workflow model of ICG-angiography integrating Standardization and Quantification (WISQ) that can be applied uniformly within the surgical innovation realm independent of the user. SUMMARY BACKGROUND DATA: Tissue perfusion based on indocyanine green (ICG)-angiography is a rapidly growing application in surgical innovation. Interpretation of results has been subjective and error-prone due to the lack of a standardized and quantitative ICG-workflow and analytical methodology. There is a clinical need for a more generic, reproducible, and quantitative ICG perfusion model for objective assessment of tissue perfusion. METHODS: In this multicenter, proof-of-concept study, we present a generic and reproducible ICG-workflow integrating standardization and quantification for perfusion assessment. To evaluate our model's clinical feasibility and reproducibility, we assessed the viability of parathyroid glands after performing thyroidectomy. Biochemical hypoparathyroidism was used as the postoperative endpoint and its correlation with ICG quantification intraoperatively. Parathyroid gland is an ideal model as parathyroid function post-surgery is only affected by perfusion. RESULTS: We show that visual subjective interpretation of ICG-angiography by experienced surgeons on parathyroid perfusion cannot reliably predict organ function impairment postoperatively, emphasizing the importance of an ICG quantification model. WISQ was able to standardize and quantify ICG-angiography and provided a robust and reproducible perfusion curve analysis. A low ingress slope of the perfusion curve combined with a compromised egress slope was indicative for parathyroid organ dysfunction in 100% of the cases. CONCLUSION: WISQ needs prospective validation in larger series and may eventually support clinical decision-making to predict and prevent postoperative organ function impairment in a large and varied surgical population.

Outcomes of parathyroidectomy versus calcimimetics for secondary hyperparathyroidism and kidney transplantation: a propensity-matched analysis.

PURPOSE: Calcimimetics are currently indicated for severe secondary hyperparathyroidism (SHPT). However, the role of parathyroidectomy (PTX) for these patients is still under debate, and its impact on subsequent kidney transplantation (KTX) is unclear. In this study, we compare the outcomes of kidney transplantation after PTX or medical treatment. METHODS: Patients who underwent KTX and had SHPT were analyzed retrospectively. Two groups were selected (patients who had either PTX or calcimimetics prior to KTX) using a propensity score for sex, age, donor type, and parathyroid hormone levels (PTH) during dialysis. The primary outcome was graft failure, and secondary outcomes were surgical KTX complications, survival, serum PTH, serum calcium, and serum phosphate levels post-KTX. RESULTS: Matching succeeded for 92 patients. After PTX, PTH was significantly lower on the day of KTX as well as at 1 and 3 years post-KTX (14.00 pmol/L (3.80-34.00) vs. 71.30 pmol/L (30.70-108.30), p < 0.01, 10.10 pmol/L (2.00-21.00) vs. 32.35 pmol/L (21.58-51.76), p < 0.01 and 13.00 pmol/L (6.00-16.60) vs. 19.25 pmol/L (13.03-31.88), p = 0.027, respectively). No significant differences in post-KTX calcium and phosphate levels were noted between groups. Severe KTX complications were more common in the calcimimetics group (56.5% vs. 30.4%, p = 0.047). There were no differences in 10-year graft failure and overall survival. CONCLUSION: PTX resulted in lower PTH after KTX in comparison to patients who received calcimimetics. Severe complications were more common after calcimimetics, but graft failure and overall survival were similar.

Timing of Parathyroidectomy Does Not Influence Renal Function After Kidney Transplantation.

BACKGROUND: Parathyroidectomy (PTx) is the treatment of choice for end-stage renal disease (ESRD) patients with therapy-resistant hyperparathyroidism (HPT). The optimal timing of PTx for ESRD-related HPT-before or after kidney transplantation (KTx)-is subject of debate. METHODS: Patients with ESRD-related HPT who underwent both PTx and KTx between 1994 and 2015 were included in a multicenter retrospective study in four university hospitals. Two groups were formed according to treatment sequence: PTx before KTx (PTxKTx) and PTx after KTx (KTxPTx). Primary endpoint was renal function (eGFR, CKD-EPI) between both groups at several time points post-transplantation. Correlation between the timing of PTx and KTx and the course of eGFR was assessed using generalized estimating equations (GEE). RESULTS: The PTxKTx group consisted of 102 (55.1%) and the KTxPTx group of 83 (44.9%) patients. Recipient age, donor type, PTx type, and pre-KTx PTH levels were significantly different between groups. At 5 years after transplantation, eGFR was similar in the PTxKTx group (eGFR 44.5 ± 4.0 ml/min/1.73 m2) and KTxPTx group (40.0 ± 6.4 ml/min/1.73 m2, p = 0.43). The unadjusted GEE model showed that timing of PTx was not correlated with graft function over time (mean difference -1.0 ml/min/1.73 m2, 95% confidence interval -8.4 to 6.4, p = 0.79). Adjustment for potential confounders including recipient age and sex, various donor characteristics, PTx type, and PTH levels did not materially influence the results. CONCLUSIONS: In this multicenter cohort study, timing of PTx before or after KTx does not independently impact graft function over time.

Safety and efficacy of subtotal or total parathyroidectomy for patients with secondary or tertiary hyperparathyroidism in four academic centers in the Netherlands.

PURPOSE: Hyperparathyroidism (HPT) is a common abnormality in patients with end-stage renal disease (ESRD). Since the introduction of cinacalcet in 2004, a shift from surgery toward predominantly medical treatment has occurred. Surgery is thought to be associated with more complications than oral medication. The aim of this retrospective study was to evaluate 30-day outcomes and effectiveness of parathyroidectomy (PTx) in ESRD patients in the Netherlands. METHODS: A national database containing data from four academic medical centers in the Netherlands of patients with ESRD-related HPT, who had undergone PTx and kidney transplantation between 1994 and 2015, was established. Primary endpoints were 30-day mortality and complication rate. Secondary endpoints were biochemical measurements. RESULTS: We identified 187 HPT patients undergoing PTx, with a median age of 46 years. Median preoperative PTH level was 866 pg/mL (interquartile range [IQR] 407-1547 pg/mL). At 3 months, the median PTH drop from baseline was 93% (IQR, 71-98%) to a median of 61 pg/mL (IQR, 23-148 pg/mL, p < 0.001). Over the 25-year inclusion period, 13 patients (7.0%) required re-exploration for persistent or recurrent disease. Thirty-day mortality and complication rate were 0.0% and 7.9% respectively. Median serum calcium levels improved significantly postoperatively from 2.6 (2.4-2.8) mmol/L to 2.3 (2.1-2.5) mmol/L (p < 0.001). CONCLUSIONS: PTx is a safe and effective procedure in the frail ESRD population. These data show that there should be no reluctance for surgical intervention and when indicated, nephrologists can safely refer these patients for PTx.

Effect of parathyroidectomy and cinacalcet on quality of life in patients with end-stage renal disease-related hyperparathyroidism: a systematic review.

BACKGROUND: Patients with end-stage renal disease (ESRD) have a decreased quality of life (QoL), which is attributable in part to ESRD-related hyperparathyroidism (HPT). Both cinacalcet and parathyroidectomy (PTx) are treatments for advanced HPT, but their effects on QoL are unclear. We performed a systematic review to evaluate the impact of cinacalcet and PTx on QoL. METHODS: A systematic literature search was performed using PubMed and EMBASE databases to identify relevant articles. The search was based on the following keywords: 'parathyroidectomy' or 'cinacalcet', 'secondary hyperparathyroidism' or 'renal hyperparathyroidism' combined with 'quality of life' or 'SF-36' or 'symptomatology'. Only studies reporting on QoL at baseline and during follow-up were included. QoL scores were extracted from the selected manuscripts and weighted means were calculated. Due to a lack of available data on QoL improvement in patients using cinacalcet, a meta-analysis could not be performed. RESULTS: In all, eight articles reached our inclusion criteria. Of this, five articles reported the effect of PTx on QoL. All PTx studies were observational and non-controlled. The physical component scores of the 36-item Medical Outcomes Study Short-Form Health Survey increased significantly with a weighted mean of 35.5% (P < 0.05). Mental component scores increased with 13.7% (P < 0.05). Parathyroidectomy assessment of symptom scores improved from 561 preoperatively to 302 postoperatively (-259 points; -46.2%). Visual analogue scale scores decreased significantly for skin itching (46.6%), joint pain (30.4%) and muscle weakness (28.7%) (P < 0.05). Three studies on the effect of cinacalcet on QoL were included, including one randomized controlled trial. None of these studies showed significant improvement of physical component and mental component scores. CONCLUSIONS: PTx improved QoL in patients treated for ESRD-related HPT, whereas cinacalcet did not. The difference in impact between PTx and cinacalcet on QoL has not been compared directly.

Management of Postthyroidectomy Hypoparathyroidism and Its Effect on Hypocalcemia-Related Complications: A Meta-Analysis.

OBJECTIVE: The aim of this Meta-analysis is to evaluate the impact of different treatment strategies for early postoperative hypoparathyroidism on hypocalcemia-related complications and long-term hypoparathyroidism. DATA SOURCES: Embase.com, MEDLINE, Web of Science Core Collection, Cochrane Central Register of Controlled Trials, and the top 100 references of Google Scholar were searched to September 20, 2022. REVIEW METHODS: Articles reporting on adult patients who underwent total thyroidectomy which specified a treatment strategy for postthyroidectomy hypoparathyroidism were included. Random effect models were applied to obtain pooled proportions and 95% confidence intervals. Primary outcome was the occurrence of major hypocalcemia-related complications. Secondary outcome was long-term hypoparathyroidism. RESULTS: Sixty-six studies comprising 67 treatment protocols and 51,096 patients were included in this Meta-analysis. In 8 protocols (3806 patients), routine calcium and/or active vitamin D medication was given to all patients directly after thyroidectomy. In 49 protocols (44,012 patients), calcium and/or active vitamin D medication was only given to patients with biochemically proven postthyroidectomy hypoparathyroidism. In 10 protocols (3278 patients), calcium and/or active vitamin D supplementation was only initiated in case of clinical symptoms of hypocalcemia. No patient had a major complication due to postoperative hypocalcemia. The pooled proportion of long-term hypoparathyroidism was 2.4% (95% confidence interval, 1.9-3.0). There was no significant difference in the incidence of long-term hypoparathyroidism between the 3 supplementation groups. CONCLUSIONS: All treatment strategies for postoperative hypocalcemia prevent major complications of hypocalcemia. The early postoperative treatment protocol for postthyroidectomy hypoparathyroidism does not seem to influence recovery of parathyroid function in the long term.

Clinical and Histopathological Risk Factors for Radioactive Iodine Refractory Follicular and Oncocytic Thyroid Carcinoma.

INTRODUCTION: Risk factors for radioactive iodine (RAI)-refractory disease in follicular (FTC) and oncocytic thyroid carcinoma (OTC) are unknown. Therefore, the aim of this study is to identify clinical and histopathological risk factors for RAI-refractory disease in FTC and OTC patients, facilitated by an extensive histopathological revision. METHODS: All adult FTC and OTC patients treated at Erasmus MC (the Netherlands) between 2000 and 2016 were retrospectively included. 2015 ATA Guidelines were used to define RAI-refractory disease. An extensive histopathological revision was performed applying the 2022 WHO Classification using Palga: Dutch Pathology Databank. Logistic regression was used to identify risk factors for RAI-refractory disease, stratified for histological subtype. RESULTS: Ninety FTC and 52 OTC patients were included, of which 14 FTC (15.6%) and 22 OTC (42.3%) developed RAI-refractory disease over a follow-up time of 8.5 years. RAI-refractory disease occurred in OTC after fewer cycles than in FTC (2.0 [IQR: 1.0-2.0] vs 2.5 [IQR: 2.0-3.75]), and it substantially decreased the 10-year disease specific survival, especially in OTC (46.4%; FTC 85.7%). In FTC, risk factors were higher age at diagnosis, pT3/pT4-stage, N1-stage, widely invasive tumors and extra-thyroidal extension. N1-stage and M1-stage were the strongest risk factors in OTC, rather than histopathological characteristics of the primary tumor. CONCLUSION: To our knowledge, this is the first study that correlates clinical and histopathological risk factors with RAI-refractory disease in FTC and OTC, facilitated by a histopathological revision. In FTC, risk factors for RAI-refractory disease were foremost histopathological characteristics of the primary tumor, whereas in OTC presentation with lymph node and distant metastasis was associated with RAI-refractory disease. Our data can help clinical decision making, particularly in patients at risk for RAI-refractory disease.

Regional Collaboration and Trends in Clinical Management of Thyroid Cancer.

OBJECTIVE: This study examines the trends in the management of thyroid cancer and clinical outcomes in the Southwestern region of The Netherlands from 2010 to 2021, where a regional collaborative network has been implemented in January 2016. STUDY DESIGN: Retrospective cohort study. SETTING: This study encompasses all patients diagnosed with thyroid cancer of any subtype between January 2010 and June 2021 in 10 collaborating hospitals in the Southwestern region of The Netherlands. METHODS: The primary outcome of this study was the occurrence of postoperative complications. Secondary outcomes were trends in surgical management, centralization, and waiting times of patients with thyroid cancer. RESULTS: This study included 1186 patients with thyroid cancer. Median follow-up was 58 [interquartile range: 24-95] months. Surgery was performed in 1027 (86.6%) patients. No differences in postoperative complications, such as long-term hypoparathyroidism, permanent recurrent nerve paresis, or reoperation due to bleeding were seen over time. The percentage of patients with low-risk papillary thyroid carcinoma referred to the academic hospital decreased from 85% (n = 120/142) in 2010 to 2013 to 70% (n = 120/171) in 2014 to 2017 and 62% (n = 100/162) in 2018 to 2021 (P < .01). The percentage of patients undergoing a hemithyroidectomy alone was 9% (n = 28/323) in 2010 to 2013 and increased to 20% (n = 63/317; P < .01) in 2018 to 2021. CONCLUSION: The establishment of a regional oncological network coincided with a de-escalation of thyroid cancer treatment and centralization of complex patients and interventions. However, no differences in postoperative complications over time were observed. Determining the impact of regional oncological networks on quality of care is challenging in the absence of uniform quality indicators.

A symptom-based algorithm for calcium management after thyroid surgery: a prospective multicenter study.

Objective: Evidence-based treatment guidelines for the management of postthyroidectomy hypocalcemia are absent. The aim of this study was to evaluate a newly developed symptom-based treatment algorithm including a protocolized attempt to phase out supplementation. Methods: In a prospective multicenter study, patients were treated according to the new algorithm and compared to a historical cohort of patients treated with a biochemically based approach. The primary outcome was the proportion of patients receiving calcium and/or alfacalcidol supplementation. Secondary outcomes were calcium-related complications and predictors for supplementation. Results: One hundred thirty-four patients were included prospectively, and compared to 392 historical patients. The new algorithm significantly reduced the proportion of patients treated with calcium and/or alfacalcidol during the first postoperative year (odds ratio (OR): 0.36 (95% CI: 0.23-0.54), P < 0.001), and persistently at 12 months follow-up (OR: 0.51 (95% CI: 0.28-0.90), P < 0.05). No severe calcium-related complications occurred, even though calcium-related visits to the emergency department and readmissions increased (OR: 11.5 (95% CI: 4.51-29.3), P <0.001) and (OR: 3.46 (95% CI: 1.58-7.57), P < 0.05), respectively. The proportional change in pre- to postoperative parathyroid hormone (PTH) was an independent predictor for supplementation (OR: 1.04 (95% CI: 1.02-1.07), P < 0.05). Conclusions: Symptom-based management of postthyroidectomy hypocalcemia and a protocolized attempt to phase out supplementation safely reduced the proportion of patients receiving supplementation, although the number of calcium-related hospital visits increased. For the future, we envision a more individualized treatment approach for patients at risk for delayed symptomatic hypocalcemia, including the proportional change in pre- to post- operative PTH.

Deescalating Follow-up After Hemithyroidectomy for Patients With Low-risk Papillary Thyroid Microcarcinoma.

Importance: Structural recurrent disease (RD) after surgical treatment of papillary thyroid microcarcinoma (mPTC) is rare. We hypothesized that the RD rate after hemithyroidectomy in low-risk patients with mPTC is low. Objective: To assess the occurrence of RD in Dutch patients with mPTC who received surgical treatment according to the Dutch guidelines. Design, Setting, and Participants: This nationwide retrospective cohort study included all patients who had undergone surgery with a diagnosis of cN0/cNx mPTC in the Netherlands between January 2000 and December 2020 were identified from the Netherlands Cancer Registry database. Patients with preoperative lymph node metastases were excluded. Two groups were defined: group 1 (incidental), mPTC in pathology report after thyroid surgery for another indication; and group 2 (nonincidental), patients with a preoperative highly suspect thyroid nodule (Bethesda 5) or proven mPTC (Bethesda 6). Dutch guidelines state that a hemithyroidectomy is sufficient in patients with unifocal, intrathyroidal mPTC. Main Outcomes and Measures: The occurrence of RD in patients with low-risk mPTC after hemithyroidectomy. Results: In total, 1636 patients with mPTC were included. Patients had a median (IQR) follow-up time of 71 (32-118) months. Median (IQR) age at time of diagnosis was 51 (41-61) years and 1292 (79.0%) were women. Overall, RD after initial treatment was seen in 25 patients (1.5%). The median (IQR) time to RD was 8.2 (3.6-16.5) months and 22 of the 25 (88%) patients developed RD within 2 years. Recurrent disease was not significantly different between both groups (group 1, n = 15 [1.3%]; group 2, n = 10 [2.1%]; difference, 0.8%; 95% CI, -0.5% to 2.5%). Of the 484 patients with nonincidental mPTC (group 2), 246 (50.8%) patients were treated with a hemithyroidectomy and follow-up in accordance with Dutch guidelines. Lymph node metastases were found in 1 of 246 (0.4%) patients after hemithyreoidectomy, and new mPTC in the contralateral thyroid was detected in 3 of 246 (1.2%) patients. Median (IQR) follow-up of this patient group was 37 (18-71) months. The 10-year probability of RD was 1.3% for patients without vascular invasion and 24.4% for patients with vascular invasion. Conclusions and Relevance: This nationwide cohort study found that overall, RD after hemithyroidectomy for patients with low-risk mPTC was rare (<2%). Based on these results, it seems reasonable to deescalate follow-up of patients with low-risk mPTC without vascular invasion after hemithyroidectomy. From a health care perspective, deescalation of follow-up may contribute to increased sustainability and accessibility to health care, both large challenges for the future.