Thymomectomy plus total thymectomy versus simple thymomectomy for early-stage thymoma without myasthenia gravis: a European Society of Thoracic Surgeons Thymic Working Group Study

Early stage thymoma and the surgical extent paradigm

The recommended treatment for early stage thymoma without myasthenia gravis is complete thymectomy (CT). Limited thymectomy (LT) (simply resecting the thymoma with safe surgical margins) is gaining popularity. In this study, we compared the surgical and oncological results of complete and limited thymectomy in non-myasthenic patients with early stage thymoma. Non-myasthenic, Masaoka stage I-II, 86 patients who underwent surgical resection for thymoma were included in the study. Complete thymectomy (n:44) included patients who had resection of the thymoma together with the entire thymus and limited thymectomy (n:42) included patients who had resection of the thymoma without remaining thymus. The surgical approach, tumor size, histological type, pathological stage, adjuvant therapy, complications, postop myasthenia gravis, recurrence and death were recorded and compared between groups. Complete thymectomy group had more WHO type B1-3 tumors, more complications and more deaths than patients in the limited thymectomy group (p = 0.03, 0.018 and 0.023 respectively). Although statistically not significant CT group had more recurrences than LT group (11.4%/4.8%, p = 0.43). The 10-year freedom from recurrence (FFR) rate in the CT group was 84.8% and in the LT group ıt was 97.6%, the difference was not statistically significant (p = 0.15). None of the factors including surgical extent analysed with univariate and multivariate analysis had a significant effect on FFR. Limited thymectomy may be a good treatment option for non-myasthenic early stage thymoma patients but randomized controlled trials with long follow-up periods, ideally comparing patients operated with minimally invasive surgery are necessary.

Long-term follow-up of non-myasthenic patients with early-stage thymoma who underwent extended thymectomy or limited resection

BACKGROUD

The standard resection for early-stage thymoma is total thymectomy and complete tumour excision with or without myasthenia gravis but the optimal surgery mode for patients with early-stage non-myasthenic thymoma is debatable. This study analysed the oncological outcomes for non-myasthenic patients with early-stage thymoma treated by thymectomy or limited resection in the long term.

METHODS

Patients who had resections of thymic neoplasms at Taipei Veteran General Hospital, Taiwan between December 1997 and March 2013 were recruited, exclusive of those combined clinical evidence of myasthenia gravis were reviewed. A total of 113 patients were retrospectively reviewed with pathologic early stage (Masaoka stage I and II) thymoma who underwent limited resection or extended thymectomy to compare their long-term oncologic and surgical outcomes.

RESULTS

The median observation time was 134.1 months [interquartile range (IQR) 90.7-176.1 months]. In our cohort, 52 patients underwent extended thymectomy and 61 patients underwent limited resection. Shorter duration of surgery (p < 0.001) and length of stay (p = 0.006) were demonstrated in limited resection group. Six patients experienced thymoma recurrence, two of which had combined myasthenia gravis development after recurrence. There was no significant difference (p = 0.851) in freedom-from-recurrence, with similar 10-year freedom-from-recurrence rates between the limited resection group (96.2 %) and the thymectomy group (93.2 %). Tumour-related survival was also not significantly different between groups (p = 0.726).result CONCLUSION: Patients with early-stage non-myasthenic thymoma who underwent limited resection without complete excision of the thymus achieved similar oncologic outcomes during the long-term follow-up and better peri-operative results compared to those who underwent thymectomy.

Relevance of robotic surgery for thymoma: a narrative review

Background and Objective

Thymectomy with median sternotomy is the gold standard for thymoma and myasthenia gravis, although minimally invasive procedures such as robot-assisted surgery have recently become more common. However, the superiority of these approaches has not been established, and they are infrequently recommended for localized lesions. The International Thymic Malignancies Interest Group warned that despite the perceived reduction in length of hospital stay and pain, the benefits of these approaches compared to the open approach have not been fully substantiated and that prospective collaborative data collection is critical in defining the value of these techniques. Whether thymectomy is necessary for stage I thymomas in the absence of myasthenia gravis or anti-acetylcholine receptor antibodies is also unclear. This study reviews and discusses the literature on this subject.

Methods

A narrative review was conducted using PubMed and Scopus databases. Original research articles comparing robotic to video-assisted thoracic surgery or to open thymectomy for thymomas were included. A comparison of partial resection and total thymectomy (thymothymectomy) for thymomas was also conducted.

Key Content and Findings

Perioperative outcomes such as blood loss, operative duration, complications, and length of hospital stay were better for robot-assisted resection of early-stage thymomas than for open thymoma surgery. It would be premature to consider partial resection as an appropriate treatment option for thymomas.

Conclusions

Robotic thymothymectomy is safe with effective and promising long-term results and oncological and surgical outcomes in patients with thymoma. Robotic thymectomy can become the standard procedure in patients with early-stage thymomas.

Robotic thymectomy in thymic tumours: a multicentre, nation-wide study

OBJECTIVES

Robotic thymectomy has been suggested and considered technically feasible for thymic tumours. However, because of small-sample series and the lack of data on long-term results, controversies still exist on surgical and oncological results with this approach. We performed a large national multicentre study sought to evaluate the early and long-term outcomes after robot-assisted thoracoscopic thymectomy in thymic epithelial tumours.

METHODS

All patients with thymic epithelial tumours operated through a robotic thoracoscopic approach between 2002 and 2022 from 15 Italian centres were enrolled. Demographic characteristics, clinical, intraoperative, postoperative, pathological and follow-up data were retrospectively collected and reviewed.

RESULTS

There were 669 patients (307 men and 362 women), 312 (46.6%) of whom had associated myasthenia gravis. Complete thymectomy was performed in 657 (98%) cases and in 57 (8.5%) patients resection of other structures was necessary, with a R0 resection in all but 9 patients (98.6%). Twenty-three patients (3.4%) needed open conversion, but no perioperative mortality occurred. Fifty-one patients (7.7%) had postoperative complications. The median diameter of tumour resected was 4 cm (interquartile range 3-5.5 cm), and Masaoka stage was stage I in 39.8% of patients, stage II in 56.1%, stage III in 3.5% and stage IV in 0.6%. Thymoma was observed in 90.2% of patients while thymic carcinoma occurred in 2.8% of cases. At the end of the follow-up, only 2 patients died for tumour-related causes. Five- and ten-year recurrence rates were 7.4% and 8.3%, respectively.

CONCLUSIONS

Through the largest collection of robotic thymectomy for thymic epithelial tumours we demonstrated that robot-enhanced thoracoscopic thymectomy is a technically sound and safe procedure with a low complication rate and optimal oncological outcomes.

Perspectives on surgical treatment for thymic epithelial tumors: a narrative review

Background and Objective

Thymic epithelial tumors are relatively rare; thus, mostly retrospective studies and a few prospective randomized controlled trials have been conducted on the treatment and the biomarkers, with no standard therapy established. Indications for extended thymectomy, robot-assisted thoracic surgery, and multidisciplinary treatment are controversial. Here, we considered the prospects of surgical treatment and the possibility of immune checkpoint inhibitor (ICI) treatment for thymic epithelial tumors.

Methods

This is a narrative review; PubMed was searched using a set of keywords related to thymoma and its proposed treatments over the last 5 years.

Key Content and Findings

Thymic epithelial tumors are associated with autoimmune diseases. They are relatively rare, and their pathology remains unclear. Therefore, accumulating more case reports is important. Surgical resection is generally considered for both diagnosis and treatment. If the tumor has a strong tendency to invade surrounding areas, such as thymic carcinoma/thymoma, the diagnosis may be confirmed preoperatively by needle biopsy, and induction chemotherapy may be selected. Surgical resection is the most effective treatment, and complete resection is important. In cases where complete resection is difficult, multidisciplinary treatment is performed. Although there are various obstacles, using ICIs may prove effective for treatment both as preoperative and postoperative chemotherapy in the future, as shown for other cancers. Programmed cell death-ligand 1 (PD-L1) is an immunoinhibitory molecule that suppresses T cells activation, leading to tumor progression. Overexpression of PD-L1 in some cancers is associated with poor clinical outcomes. However, the role of PD-L1 expression as a prognostic factor remains controversial. Therefore, various biomarkers other than PD-L1 have been identified.

Conclusions

We reviewed the latest treatments for thymic epithelial tumors. If new therapeutic agents such as ICIs and molecular-targeted drugs are developed, this review suggests that surgery will become more important not only as therapy but also as part of multidisciplinary treatment that includes tissue collection.

Practical methods to differentiate thymic malignancies by positron-emission tomography and tumor markers

PURPOSE

An accurate diagnosis of thymic malignancies is important, but challenging due to the broad range of differential diagnoses. This study aims to evaluate the efficacy of PET/CT and tumor markers for diagnosing thymic malignancies.

METHODS

Patients admitted to our department between January 2012 and December 2021 with primary anterior mediastinal tumors were retrospectively evaluated. We evaluated the relationship between the maximum standardized uptake value (SUVmax), tumor markers, and pathological diagnosis in four groups: thymic carcinoma, thymoma, lymphoma, and others.

RESULTS

In total, 139 patients were included in this study. The SUVmax was significantly higher in lymphoma, thymic carcinoma, and thymoma, in that order. The cytokeratin 19 fragment (CYFRA 21-1) was significantly higher in thymic carcinoma than in the other groups. An ROC curve analysis indicated that the optimal cut-off values of SUVmax for thymic carcinoma plus lymphoma and CYFRA 21-1 for thymic carcinoma were 7.97 (AUC = 0.934) and 2.95 (AUC = 0.768), respectively. Using a combination of cut-off values (SUVmax = 8, CYFRA 21-1 = 3), the accuracy rate for diagnosing thymic carcinoma was 91.4%.

CONCLUSIONS

The SUVmax and CYFRA 21-1 levels are significant indicators for the diagnosis of thymic carcinoma. Combining these indicators resulted in a more accurate diagnosis of thymic malignancies, which could facilitate the decision-making process for determining the optimal treatment strategies.

Perioperative outcomes comparison of robotic and video-assisted thoracoscopic thymectomy for thymic epithelial tumor: a single-center experience

BACKGROUND

The advent of robot-assisted thoracoscopic surgery (RATS) has completely revolutionized the modality of thymectomy, which could reportedly achieve equivalent efficacy compared with a minimally invasive approach. This study was conducted to further compare the perioperative outcomes between these two modalities.

METHODS

A retrospective single-center study that included patients receiving either a robotic or video-assisted thoracoscopic (VAT) thymectomy between February 2021 and January 2023 was conducted. All the patients were pathologically confirmed with thymic epithelial tumors. Clinical and pathological characteristics and perioperative outcomes were collected and compared between these two cohorts.

RESULTS

A total of 190 patients were included in this study, with 61 (32.1%) and 129 (67.9%) receiving robotic and video-assisted thymectomy, respectively. The clinicopathological characteristics were not significantly different between these 2 groups. The size of the resected specimens in the RATS cohort was larger than the VATS cohort [median (IQR), 13.0 (8.0-16.0) vs. 9.0 (6.7-12.0) cm, p < 0.001], while the procedural duration was longer for the RATS group than its counterpart [median (IQR), 105 (85-143) vs. 85 (69-115) min, p = 0.001]. Moreover, no other significant difference was observed between these two groups. Since more than half of the robotic thymectomy was performed using a subxiphoid approach, a subgroup analysis was further conducted. Similarly, the robotic group through a subxiphoid approach harbored a longer procedural duration, and the size of the specimens obtained was larger than the VATS group [median (IQR), 14.0 (11.0-16.5) vs. 12.5 (8.5-15.0) cm, p = 0.061].

CONCLUSIONS

The early clinical efficacy of robotic thymectomy was proven comparable to the established VATS approach, and such a modality might have strength when obtaining larger specimens, which could contribute to improving long-term efficacy. Despite the longer procedural duration recorded in the early stage of conducting robotic thymectomy, further accumulation would help decrease the time.

Dataset for reporting of thymic epithelial tumours: recommendations from the International Collaboration on Cancer Reporting (ICCR)

AIMS

Thymic epithelial tumours (TET), including thymomas and thymic carcinomas and thymic neuroendocrine neoplasms, are malignant neoplasms that can be associated with morbidity and mortality. Recently, an updated version of the World Health Organization (WHO) Classification of Thoracic Tumours 5th Edition, 2021 has been released, which included various changes to the classification of these neoplasms. In addition, in 2017 the Union for International Cancer Control (UICC) / American Joint Committee on Cancer (AJCC) published the 8th Edition Staging Manual which, for the first time, includes a TNM staging that is applicable to thymomas, thymic carcinomas, and thymic neuroendocrine neoplasms.

METHODS AND RESULTS

To standardize reporting of resected TET and thymic neuroendocrine neoplasms the accrediting bodies updated their reporting protocols. The International Collaboration on Cancer Reporting (ICCR), which represents a collaboration between various National Associations of Pathology, updated its 2017 histopathology reporting guide on TET and thymic neuroendocrine neoplasms accordingly. This report will highlight important changes in the reporting of TET and thymic neuroendocrine neoplasms based on the 2021 WHO, emphasize the 2017 TNM staging, and also comment on the rigour and various uncertainties for the pathologist when trying to follow that staging.

CONCLUSION

The ICCR dataset provides a comprehensive, standardized template for reporting of resected TET and thymic neuroendocrine neoplasms.

Prognosis and surgical outcomes of the total thymectomy versus thymomectomy in non-myasthenic patients with early-stage thymoma: A systematic review and meta-analysis

Whether thymectomy (TM) or thymomectomy (TMM) is better for non-myasthenic patients with early-stage thymoma. We conducted a meta-analysis to compare the clinical outcomes and prognoses of non-myasthenic patients with early-stage thymoma treated using thymectomy versus thymomectomy. PubMed, Embase, Cochrane Library and CNKI databases were systematically searched for relevant studies on the surgical treatment (TM and TMM) of non-myasthenic patients with early-stage thymoma published before March 2022. The Newcastle-Ottawa scale was used to evaluate the quality of the studies, and the data were analyzed using RevMan version 5.30. Fixed or random effect models were used for the meta-analysis depending on heterogeneity. Subgroup analyses were performed to compare short-term perioperative and long-term tumor outcomes. A total of 15 eligible studies, including 3023 patients, were identified in the electronic databases. Our analysis indicated that TMM patients might benefit from a shorter duration of surgery (p = 0.006), lower blood loss volume (p < 0.001), less postoperative drainage (p = 0.03), and a shorter hospital stay (p = 0.009). There were no significant differences in the overall survival rate (p = 0.47) or disease-free survival rate (p = 0.66) between the two surgery treatment groups. Likewise, TM and TMM were similar in the administration of adjuvant therapy (p = 0.29), resection completeness (p = 0.38), and postoperative thymoma recurrence (p = 0.99). Our study revealed that TMM might be a more appropriate option in treating non-myasthenic patients with early-stage thymoma.

Prognostic factors and role of postoperative radiotherapy in surgically resected thymomas

Objective

To investigate the prognostic factors in and role of postoperative radiotherapy (PORT) for surgically resected thymomas.

Methods

A total of 1540 patients with pathologically confirmed thymomas undergoing resection between 2000 and 2018 were identified retrospectively from the SEER (Surveillance, Epidemiology, and End Results) database. Tumors were restaged as local (limited to thymus), regional (invasion to mediastinal fat and other neighboring structures), or distant stage. Disease-specific survival (DSS) and overall survival (OS) were estimated by the Kaplan-Meier method and the log-rank test. Adjusted hazard ratios (HRs) with 95% CIs were calculated by Cox proportional hazards modeling.

Results

Tumor stage and histology were independent predictors of both DSS (regional: HR, 3.711; 95% CI, 2.006-6.864; distant: HR, 7.920; 95% CI, 4.061-15.446; type B2/B3: HR, 1.435; 95% CI, 1.008-2.044) and OS (regional: HR, 1.461; 95% CI, 1.139-1.875; distant: HR, 2.551; 95% CI, 1.855-3.509; type B2/B3: HR, 1.409; 95% CI, 1.153-1.723). For patients with regional stage and type B2/B3 thymomas, PORT was associated with better DSS after thymectomy/thymomectomy (HR, 0.268; 95% CI, 0.099-0.727), but the association was not significant after extended thymectomy (HR, 1.514; 95% CI, 0.516-4.44). Among patients with lymph node metastases, those who received PORT (HR, 0.372; 95% CI, 0.146-0.949), chemotherapy (HR, 0.843; 95% CI, 0.303-2.346), or both (HR, 0.296, 95% CI, 0.071-1.236) had a better OS.

Conclusions

The extent of invasion and tumor histology were independent predictors of worse survival following surgical resection of thymoma. Patients with regional invasion and type B2/B3 thymoma who undergo thymectomy/thymomectomy may benefit from PORT, while patients with nodal metastases may benefit from multimodal therapy, including PORT and chemotherapy.

Rapid imaging of thymoma and thymic carcinoma with a fluorogenic probe targeting γ-glutamyltranspeptidase

In recent years, thoracoscopic and robotic surgical procedures have increasingly replaced median sternotomy for thymoma and thymic carcinoma. In cases of partial thymectomy, the prognosis is greatly improved by ensuring a sufficient margin from the tumor, and therefore intraoperative fluorescent imaging of the tumor is especially valuable in thoracoscopic and robotic surgery, where tactile information is not available. γ-Glutamyl hydroxymethyl rhodamine green (gGlu-HMRG) has been applied for fluorescence imaging of some types of tumors in the resected tissues, and here we aimed to examine its validity for the imaging of thymoma and thymic carcinoma. 22 patients with thymoma or thymic carcinoma who underwent surgery between February 2013 and January 2021 were included in the study. Ex vivo imaging of specimens was performed, and the sensitivity and specificity of gGlu-HMRG were 77.3% and 100%, respectively. Immunohistochemistry (IHC) staining was performed to confirm expression of gGlu-HMRG's target enzyme, γ-glutamyltranspeptidase (GGT). IHC revealed high GGT expression in thymoma and thymic carcinoma in contrast to absent or low expression in normal thymic parenchyma and fat tissue. These results suggest the utility of gGlu-HMRG as a fluorescence probe for intraoperative visualization of thymomas and thymic carcinomas.

Prognostic factors and genetic markers in thymic epithelial tumors: A narrative review

Thymic epithelial tumors (TET) are a group of rare neoplasms of the anterior mediastinum comprising thymomas and thymic carcinomas. The carcinogenesis of TET is mostly unknown. Many studies, mostly retrospective case series, have tried to establish prognostic factors in TET. TET is a very heterogeneous group of tumors with many subtypes for which diagnosis and treatment remains a very challenging task. Despite the disparities among retrospective studies, there are some prognostic factors that are more pertinent such as the completeness of resection, TNM stage and the Masaoka-Koga classification. On the other hand, the identification of different genetic pathways that result in the pathogenesis of TET represents a fascinating field of study that could possibly lead to the development of new targeted therapies. The aim of this review is to discuss the different prognostic factors and genetic markers of TET. The meticulous use of national and international databases could provide sufficient number of patients in order to draw more valid conclusions.

Histological Classification and Invasion Prediction of Thymoma by Machine Learning-Based Computed Tomography Imaging

Purpose

The values of machine learning-based computed tomography (CT) imaging in histological classification and invasion prediction of thymoma were investigated.

Methods

181 patients diagnosed with thymoma by surgery or biopsy in Shantou Central Hospital between February 2017 and March 2022 were selected. According to the concept of simplified histological classification and the latest histological classification by the WHO, thymoma was divided into two groups, including low-risk (types A, AB, B1, and metaplastic type) and high-risk groups (types B2 and B3). CT images were reconstructed by filtering back projection (FBP) algorithm. CT image features were collected for statistical analysis.

Results

The main symptoms of patients diagnosed with thymoma included respiratory tract infection, chest distress and shortness of breath, and chest pain. 35.91% of them suffered from complicated myasthenia gravis. Tumor size and position in low-risk and high-risk groups showed no statistical significance (P > 0.05). Tumor morphology and boundary between the two groups suggested statistical difference (P < 0.05). Whether tumor invaded adjacent tissues was apparently correlated with simplified histological classification (P < 0.01). The sensitivity and specificity of CT images for the invasion of mediastinal pleura or pericardium were around 90% and negative predictive values both reached above 95%. Those of the CT images for lung invasion were over 80%. The negative and positive predictive values were 93.54% and 63.82%, respectively. Those of the CT images for blood vessel invasion were 67.32% and 97.93%. The negative and positive predictive values were 98.21% and 83%, respectively.

Conclusion

The machine learning-based CT image had significant values in the prediction of different histological classification and even invasion level.

Therapeutic options in thymomas and thymic carcinomas

INTRODUCTION

Radical surgery is the best therapeutic option for thymic malignancies. However, patients with advanced or recurrent thymic malignancies often require chemotherapy or radiotherapy. Since thymic malignancies are rare cancers, the efficacy and safety of treatments have been verified based on small Phase 2 trials or retrospective studies.

AREA COVERED

We comprehensively reviewed the treatment strategies for thymic malignancies, including surgery, radiotherapy, and pharmacotherapy, including cytotoxic chemotherapy, molecular-targeted therapy, and immunotherapy. Additionally, we reviewed specific situations, such as pleural dissemination, central nervous system metastasis, and paraneoplastic syndrome.

EXPERT OPINION

Cytotoxic chemotherapy remains the standard option in pharmacotherapy. However, multikinase inhibitors, such as sunitinib and lenvatinib, and immune checkpoint inhibitors including pembrolizumab have been developed to treat thymic carcinomas. Now, a Phase 2 study is evaluating whether lenvatinib plus pembrolizumab benefits patients with type B3 thymoma or thymic carcinoma. Phosphatidylinositol 3-kinase/AKT/ mammalian target of rapamycin inhibitors may contribute to disease control and octreotide scan is only applicable to somatostatin analogues. Although the genomic characteristics of thymic malignancies have been analyzed, few actionable mutations have been detected in general. The development of a treatment strategy using combination pharmacotherapy is anticipated.