The International Association for the Study of Lung Cancer Thymic Epithelial Tumor Staging Project: Proposal for the T Component for the Forthcoming (Ninth) Edition of the TNM Classification of Malignant Tumors

Risk factors and prognostic factors of pleural metastases in thymic epithelial tumors: A narrative review

INTRODUCTION

Pleural metastases are common in thymic epithelial tumors (TET), which include pleural recurrence and stage IVa at initial diagnosis. However, the specific risk factors predicting its recurrence (i.e., pleural recurrence group) and prognostic factors for pleural metastasis (i.e., stage IVa) remain unclear. This review aims to identify and discuss the predictors associated with pleural metastases in patients with TET.

METHODS

A systematic literature search was conducted on PubMed, MEDLINE, Embase, and Cochrane for articles published between 1/1/1990 and 3/11/2023. The selection process was independently carried out by three researchers, and the quality of the selected papers was assessed using the Newcastle-Ottawa Scale (NOS).

RESULTS

Out of the 4932 papers reviewed, 22 were included in the final analysis: 15 papers on risk factors of pleural recurrence after primary treatment(i.e., recurrence group) and 7 papers on the prognostic factors of patients with stage IVa at diagnosis(i.e., stage IVa group). Of the 15 former articles, 5 identified pleural invasion and invasion of other tissues as significant risk factors for pleural recurrence. Four of 15 papers identified the Masaoka-Koga stage as a significant risk factor, while two of 15 papers identified the contact length between the tumor contour and the lung as a contributing factor for pleural recurrence. Additionally, two papers suggested that tumor size may be a risk factor for pleural recurrence. Six other papers discussed various factors, including a lobulated tumor contour, WHO histologic classifications B2 and B3, radiotherapy doses of≤50Gy, incomplete resection, and Entire hemithorax radio therapy, as potential risk factors. Furthermore, one paper specifically addressed the decreased risk for pleural dissemination associated with Video-Assisted Thoracoscopic Surgery (VATS) thymectomy. In patients with stage IVa at diagnosis group, three of 7 papers mentioned that resection influenced the prognosis. Two papers discussed the number of nodules in the pleura but arrived at different conclusions. One paper suggested that patients older than 50 years might have worse outcomes, while another analyzed the invasion of structures but did not find any significant results.

CONCLUSION

For pleural recurrence patients, the most commonly discussed risk factor is pleural invasion. Other identified risk factors include the Masaoka-Koga stage, contact length between the tumor contour and the lung, tumor size, lobulated tumor contour, WHO histologic classifications B2 and B3, radiotherapy doses of≤50Gy, and incomplete resection. For patients with stage IVa at diagnosis, non--extrapleural pneumonectomy, incomplete or no resection, and histological subtype may contribute to a poorer prognosis in patients diagnosed with pleural dissemination. The number of disseminated pleural nodules remains controversial and may be correlated with resectability.

Tumour dimension is a prognostic factor in thymic epithelial tumours: An update analysis from the ESTS thymic database: Tumour dimension in thymic tumours

OBJECTIVE

The 9thTNM proposal for thymic epithelial tumours (TETs) introduced size as category in stage I, confirming tumour infiltration type as descriptor for the other stages. Aim of this study is to evaluate the role of tumour size in TETs considering different possible cut-offs also among different subgroups.

MATERIAL AND METHODS

Clinical and pathological data of patients from ESTS thymic database who underwent surgery for TETs from1/2000 to 12/2022 were reviewed and analysed. Patients clinical data, tumour characteristics, size and organs infiltration were collected and correlated to overall survival (OS), Disease free Survival (DFS) and Cancer specific Survival (CSS) using Kaplan Meier curves. The log-rank test was used to assess differences between subgroups. A multivariable model was built using Cox-regression analysis including clinical relevant variables resulting significant at univariable (p-value < 0.05).

RESULTS

The final analysis was conducted on 2146 patients. Most patients presented tumours size >5 cm(59 %)and without surrounding structures infiltrations (51.3 %). During FUP, a recurrence occurred in 235 (11%) patients, 199 (9.3%) died, 38 due to tumour progression. Multivariable confirmed as independent negative prognostic factors age (p < 0.001), carcinoma/NETT histology (p < 0.001),TETs size >5 cm (p < 0.001, HR 2.16; 95 %CI 1.32-3.50), and infiltration (p = 0.04) for OS; advanced TNM STAGE 9th edition (p < 0.001) and carcinoma/NETT (p = 0.001) for DFS; infiltration presence (p < 0.001) and carcinoma/NETT (p < 0.001) for CSS. Significant differences in OS, DFS and CSS were present considering size cut-off 5 cm (p < 0.001, p < 0.001 and p = 0.001, respectively), while using 3 cm cut-off only DFS (p < 0.001) and CSS (p = 0.001) resulted statistically significant. Significant differences in OS, DFS and CSS were present considering surrounding organ infiltration in TETs ≤ 5 cm (p = 0.004, p < 0.001 and p = 0.001) and in TETs > 5 cm (p = 0.024, p < 0.001 and p < 0.001).

CONCLUSIONS

Tumour size resulted a significant prognosticator in TETs, and its associations with infiltration permits to identify different prognostic groups.

Robotic-assisted extended thymectomy for large resectable thymoma: 21 years' experience

OBJECTIVE

This study aims to evaluate the perioperative and midterm oncological outcomes of robotic-assisted thoracic surgery extended thymectomy for patients with large resectable thymomas compared with small thymomas.

METHODS

This retrospective single-center study included 204 patients with thymomas who underwent robotic-assisted thoracic surgery extended thymectomy between January 2003 and February 2024. Patients were divided into 2 groups based on the thymoma size (5-cm threshold).

RESULTS

The study comprised 114 patients (55.9%) in the small thymoma group and 90 patients (44.1%) in the large thymoma group. No significant differences were found between the groups regarding gender, age, proportion of elderly patients, or pathologic high-risk classifications. Apart from a longer operative time (P = .009) in the large thymoma group, no differences were observed between the 2 groups regarding surgical parameters and postoperative outcomes. No deaths occurred within 30 days in either group. During a median follow-up of 61.0 months (95% CI, 48.96-73.04), 4 patients experienced recurrence (1.96%). No significant differences in the 5-year overall survival (P = .25) or recurrence-free survival (P = .43) were observed between groups.

CONCLUSIONS

Robotic-assisted thoracic surgery extended thymectomy is technically feasible, safe, and effective for treating large resectable thymomas. Moreover, midterm outcomes for patients with completely resected large thymomas were comparable to those with small thymomas during a median follow-up period of up to 5 years.

The Ninth Edition TNM Staging Classification for Thymic Epithelial Tumors

Staging classification is essential in cancer management and is based on three components: tumor extent (T), lymph node involvement (N), and distant metastatic disease (M). For thymic epithelial malignancies, clinical Tumour, Node, Metastasis (cTNM) staging is primarily determined by imaging, making radiologists integral to clinical practice, treatment decisions, and maintaining the quality of staging databases. The ninth edition of the TNM classification for thymic epithelial tumors will be implemented in January 2025. This review outlines the definitions for the TNM categories in the updated edition, provides examples, and elaborates on the radiologist's role and imaging considerations.

Investigating the impact of tumor size on survival outcomes in thymoma and thymic carcinoma patients using the SEER database

This study aims to clarify the impact of tumor size on the prognosis of patients diagnosed with thymoma and thymic carcinoma, leveraging data from a population-based registry. Utilizing the SEER database, this retrospective analysis identified patients diagnosed with thymoma and thymic carcinoma from 2000 to 2020. Propensity score matching was employed to mitigate potential statistical biases between groups categorized by tumor size (≤ 6.5 cm and > 6.5 cm). The study included a total of 3857 patients, comprising 2688 with thymoma and 1169 with thymic carcinoma. Multivariate analysis demonstrated that tumors ≤ 6.5 cm independently correlated with improved Cancer-Specific Survival (CSS) (p = 0.001; p < 0.001) and Overall Survival (OS) (p < 0 .001; p < 0.001) in both thymoma and thymic carcinoma cohorts. Subgroup analysis revealed that smaller tumors (≤ 6.5 cm) conferred survival benefits in patients with Masaoka-Koga stage IIB thymomas and stage III/IV thymic carcinomas (thymoma: CSS: p < 0.0001; OS: p = 0.00045; thymic carcinoma: CSS: p = 0.028; OS: p = 0.014). Additionally, WHO type A/AB/B1 and type B2/B3 thymomas with tumors ≤ 6.5 cm exhibited superior CSS (p = 0.005; p < 0.00018) and OS (p = 0.015; p = 0.0021). Through propensity matching analysis utilizing the SEER database, this study underscores the prognostic significance of tumor size in both early-stage thymoma and advanced-stage thymic carcinoma, identifying a critical threshold of 6.5 cm. In the WHO classification, tumor size based on the cut-off value of 6.5 cm has a greater impact on the prognosis of type B2/B3 (high-risk group) than A/AB/B1 (low-risk group).

RadioGraphics Update: The Ninth Edition TNM Staging System for Thymic Epithelial Tumors

Editor's Note.-RadioGraphics Update articles supplement or update information found in full-length articles previously published in RadioGraphics. These updates, written by at least one author of the previous article, provide a brief synopsis that emphasizes important new information such as technological advances, revised imaging protocols, new clinical guidelines involving imaging, or updated classification schemes.

The Prognostic Role of the Number of Involved Structures in Thymic Epithelial Tumors: Results from the ESTS Database

BACKGROUND

The role of the number of involved structures (NIS) in thymic epithelial tumors (TETs) has been investigated for inclusion in future staging systems, but large cohort results still are missing. This study aimed to analyze the prognostic role of NIS for patients included in the European Society of Thoracic Surgeons (ESTS) thymic database who underwent surgical resection.

METHODS

Clinical and pathologic data of patients from the ESTS thymic database who underwent surgery for TET from January 2000 to July 2019 with infiltration of surrounding structures were reviewed and analyzed. Patients' clinical data, tumor characteristics, and NIS were collected and correlated with CSS using Kaplan-Meier curves. The log-rank test was used to assess differences between subgroups. A multivariable model was built using logistic regression analysis.

RESULTS

The final analysis was performed on 303 patients. Histology showed thymoma for 216 patients (71.3%) and NET/thymic carcinoma [TC]) for 87 patients (28.7%). The most frequently infiltrated structures were the pleura (198 cases, 65.3%) and the pericardium in (185 cases, 61.1%), whereas lung was involved in 96 cases (31.7%), great vessels in 74 cases (24.4%), and the phrenic nerve in 31 cases (10.2%). Multiple structures (range, 2-7) were involved in 183 cases (60.4%). Recurrence resulted in the death of 46 patients. The CSS mortality rate was 89% at 5 years and 82% at 10 years. In the univariable analysis, the favorable prognostic factors were neoadjuvant therapy, Masaoka stage 3, absence of metastases, absence of myasthenia gravis, complete resection, thymoma histology, and no more than two NIS. Patients with more than two NIS presented with a significantly worse CSS than patients with no more than two NIS (CSS 5- and 10-year rates: 9.5% and 83.5% vs 93.2% and 91.2%, respectively; p = 0.04). The negative independent prognostic factors confirmed by the multivariable analysis were incomplete resection (hazard ratio [HR] 2.543; 95% confidence interval [CI] 1.010-6.407; p = 0.048) and more than two NIS (HR 1.395; 95% CI 1.021-1.905; p = 0.036).

CONCLUSIONS

The study showed that more than two involved structures are a negative independent prognostic factor in infiltrative thymic epithelial tumors that could be used for prognostic stratification.

Making an accurate diagnosis of anterior mediastinal lesions: a proposal for a new diagnostic algorithm from the BTOG Thymic Malignancies Special Interest Group

Due to the rising demand in cross-sectional thoracic imaging, anterior mediastinal lesions are being identified with increasing frequency. Following iterative and multidisciplinary discussions, the BTOG Thymic Malignancies Special Interest Group have developed an algorithm to standardise the diagnostic approach for these relatively uncommon but important conditions which span from benign (thymic remnant, thymic hyperplasia and thymic cysts) to suspected localised thymomas to suspected more aggressive malignancy (thymic carcinoma, lymphoma and germ cell tumours). For each condition, we provide a brief description, an overview of the key radiological findings and a description of the proposed algorithm including the rationale behind the recommendations. We also highlight the role of magnetic resonance (MR) imaging for the characterisation of anterior mediastinal masses in specific indications when the necessary local resources and expertise exist. In addition, we hope this provides the rationale for service development in MR of the anterior mediastinum where current resource and expertise requires development. Through this standardised pathway, we hope to drive improvements in patient care by rationalising surveillance schedules, avoiding unnecessary resections of benign entities with their associated morbidity and optimising the diagnostic work-up prior to the appropriate treatment of anterior mediastinal malignancies.

Postoperative Radiation Therapy for Thymic Carcinoma: An Analysis of the International Thymic Malignancy Interest Group/European Society of Thoracic Surgeons Database

INTRODUCTION

R0 resection and radiation therapy have been associated with improved overall survival (OS) in patients with thymic carcinoma (TC). Here, we analyzed which subgroups of patients derive the greatest benefit from postoperative radiation therapy (PORT).

METHODS

Clinical, pathologic, treatment, and survival information of 462 patients with TC from the International Thymic Malignancy Interest Group/European Society of Thoracic Surgeons database were analyzed. Variables included age, sex, continent of treatment, paraneoplastic syndrome, carcinoma subtype, tumor size, pathologic Masaoka stage, resection status, and use of chemotherapy. OS was the primary end point using the Kaplan-Meier method. Time to recurrence (TTR) was the secondary end point using a competing risk analysis. A 3-month landmark analysis was performed.

RESULTS

PORT was associated with a significant OS benefit (5-y OS 68% versus 53%, p = 0.002). In patients with R0 resection, PORT was associated with increased OS for advanced (stages III-IV, p = 0.04), but not early (stages I-II, p = 0.14) stage TC. In patients with an R1/2 resection of advanced-stage TC, PORT was associated with significantly longer OS (5-y OS 53% versus 38%; p < 0.001). Subset analyses did not reveal clear associations of PORT with TTR. On multivariable analysis, lower pathologic stage, PORT, and R0 resection status were associated with an OS benefit, whereas only higher age and lower pathologic stage had an association with longer TTR.

CONCLUSIONS

In the largest individual patient data set on patients with TC reported to date, PORT was associated with a meaningful OS benefit in patients with advanced-stage TC after an R0 or R1/2 resection.

International reproducibility study of thymic epithelial tumors staging: pT stage is an issue. proposals for improvement. A RYTHMIC/ITMIG study

INTRODUCTION

Pathologists are staging thymic epithelial tumors (TET) according to the 8th UICC/AJCC TNM system. Within the French RYTHMIC network, dedicated to TET, agreement on pathologic tumor stage (pT) among the pathology panelists was difficult. The aim of our study was to determine the interobserver reproducibility of pT at an international level, to explore the source of discrepancies and potential interventions to address these.

METHODS

An international panel of pathologists was recruited through the International Thymic Malignancy Interest Group (ITMIG). The study focused on invasion of mediastinal pleura, pericardium, and lung. From a cohort of cases identified as challenging within the RYTHMIC network, we chose a series of test and validation cases (n = 5 and 10, respectively).

RESULTS

Reproducibility of the pT stage was also challenging at an international level as none of the 15 cases was classified as the same pT stage by all ITMIG pathologists. The agreement rose from slight (κ = 0.13) to moderate (κ = 0.48) between test and validation series. Discussion among the expert pathologists pinpointed two major reasons underlying discrepancies: 1) Thymomas growing with their "capsule" and adhering to the pleurae, pericardium, or lung were often misinterpreted as invading these structures. 2) Recognition of the mediastinal pleura was identified as challenging.

CONCLUSION

Our study underlines that the evaluation of the pT stage of TET is problematic and needs to be addressed in more detail in an upcoming TNM classification. The publication of histopathologic images of landmarks, including ancillary tests could improve reproducibility for future TNM classifications.

TNM Staging System in Thymoma: A Critical Appraisal?

Thymomas are rare tumors of the anterior mediastinum with peculiar clinical and pathological features. They have been deeply analyzed by pioneer authors, who strictly linked their name to the main pathological and staging classifications. Before the latest edition of the WHO classification of thymic epithelial tumors, the history of thymoma pathological classification inherited the name of the pathologists who systematically addressed the issue, from Levine-Rosai to Muller-Hermelink. Similarly, the thymoma staging system is intimately related to the name of two surgeons, Masaoka and Koga, who historically dealt with this disease. More recently, the traditional tumor-nodes-metastasis (TNM) system has been developed for the staging of this condition, in a rational attempt to put thymomas in conformity with the other solid tumors. The efforts of the International Thymic Malignancies Interest Group (ITMIG) and the Thymic Domain of the Staging and Prognostic Factors Committee (TD-SPFC) of the International Association for the Study of Lung Cancer (IASLC) resulted in the TNM classification of thymic tumors, which have been included in the eighth edition of the American Joint Committee on Cancer's (AJCC) Cancer Staging Manual. Herein, we report a narrative review of the evolution of the thymic epithelial tumors (TET) staging system and present a critical appraisal of the actual TNM classification compared with the historical Masaoka-Koga classification, with special focus on the proposal for the ninth edition of the TNM, expected in 2024.

The International Association for the Study of Lung Cancer Thymic Epithelial Tumors Staging Project: Proposals for the N and the M Components for the Forthcoming (Ninth) Edition of the TNM Classification of Malignant Tumors

INTRODUCTION

Stage classification is an important underpinning of management in patients with cancer and rests on a combination of three components-T for tumor extent, N for nodal involvement, and M for distant metastases. This article details the revision of the N and the M components of thymic epithelial tumors for the ninth edition of the TNM classification of malignant tumors proposed by the Thymic Domain of the International Association for the Study of Lung Cancer Staging and Prognostic Factors Committee.

METHODS

The N and M components of the eighth edition staging system were verified by a large international collaborative data source through a data-driven analysis. A total of 9147 cases were included for analysis, including 7662 thymomas, 1345 thymic carcinomas, and 140 neuroendocrine thymic tumors.

RESULTS

Lymph node involvement rates were 1.5% in thymomas and 17.6% and 27.7% in thymic carcinomas and neuroendocrine thymic tumors, respectively. Rates of lymph node metastasis were increasingly higher in tumors with higher T stage and higher-grade histologic type. Survival analysis validated the differences in the N and M categories proposed in the eighth edition staging system. Good discrimination in overall survival was detected among pathologic (p)N and pM categories in patients with thymoma and thymic carcinoma.

CONCLUSIONS

No changes are proposed from the eighth edition for the N and M components. The proposed stage classification will provide a useful tool for management of the disease among the global thymic community.

What's new in thoracic oncology

Many changes have occurred in the field of thoracic surgery over the last several years. In this review, we will discuss new diagnostic techniques for lung cancer, innovations in surgery, and major updates on latest treatment options including immunotherapy. All these have significantly started to change our approach toward the management of lung cancer and have great potential to improve the lives of our patients afflicted with this disease.

The International Association for the Study of Lung Cancer Thymic Epithelial Tumors Staging Project: Proposal for a Stage Classification for the Forthcoming (Ninth) Edition of the TNM Classification of Malignant Tumors

INTRODUCTION

A TNM-based system for all types of thymic epithelial tumors was introduced in the eighth edition of the TNM classification of thoracic malignancies. The Thymic Domain of the Staging and Prognostic Factors Committee of the International Association for the Study of Lung Cancer, composed of multispecialty international experts, was charged to develop proposals for the ninth edition. This article outlines the proposed definitions for the T, the N, and the M components and their combination into stage groups.

METHODS

A large central database of 11,347 patients with thymic epithelial tumors was assembled thanks to the contribution of the major thymic organizations worldwide and analyses were carried out for the T, the N, and the M components and the stage groups. Overall survival was the outcome measure for patients with completely and incompletely resected tumors, and recurrence for those with complete resection. When the number of patients was sufficient, analyses were performed separately for thymomas, thymic carcinomas, and neuroendocrine thymic tumors.

RESULTS

Tumor size is included in the T1 category as T1a (≤5cm) and T1b (>5 cm); the mediastinal pleura is dropped as a T descriptor; invasion of the lung or phrenic nerve is reclassified as T2 (instead of T3). No changes are proposed for the N and the M components from the eighth edition. The stage groups remain the same.

CONCLUSIONS

The proposed changes for the ninth edition of the TNM classification set the stage for further progress in the future for these rare tumors.

The International Association for the Study of Lung Cancer Thymic Epithelial Tumors Staging Project: An Overview of the Central Database Informing Revision of the Forthcoming (Ninth) Edition of the TNM Classification of Malignant Tumors

INTRODUCTION

In 2014, a TNM-based system for thymic epithelial tumors was proposed. The TNM stage classification system was published as a result of a joint project from the International Association for the Study of Lung Cancer and the International Thymic Malignancy Interest Group for the eighth edition of the American Joint Commission on Cancer and the Union for International Cancer Control stage classification system. The Thymic Domain of the Staging and Prognostic Factors Committee of the International Association for the Study of Lung Cancer received the mandate to make proposals for the ninth edition of the TNM stage classification.

METHODS

A central thymic database was collected by the Cancer Research And Biostatistics with the contribution of the major thymic associations in the world.

RESULTS

A total of 11,347 patients were collected. Submitting organizations were the following: Japanese Association for Research in the Thymus, European Society of Thoracic Surgeons, Chinese Alliance for Research in Thymoma, Korean Association for Research in the Thymus, International Thymic Malignancy Interest Group, and Réseau tumeurs THYMiques et Cancer. Additional contributions came from centers in the United States, United Kingdom, Turkey, Australia, Spain, and Italy. A total of 9147 cases were eligible for analysis. Eligible cases for analysis came from Asia and Australia (5628 cases, 61.5%), Europe (3113 cases, 34.0%), and North America (406 cases, 4.4%).

CONCLUSIONS

This report provides an overview of the database that has informed the proposals for the updated T, N, and M components and the stage groups for the ninth TNM of malignant tumors.