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.

The International Association for the Study of Lung Cancer Thymic Epithelial Tumor Staging Project: A Re-Assessment of the International Thymic Malignancy Interest Group/International Association for the Study of Lung Cancer Lymph Node Map for Thymic Epithelial Tumors for the Forthcoming Ninth Edition of the TNM Classification of Malignant Tumors

INTRODUCTION

A lymph node map is the pillar on which accurate assignment and documentation of nodal classification stands. The International Thymic Malignancy Interest Group created the first map for thymic epithelial malignancies in conjunction with the eighth edition of the TNM classification, representing the first official TNM classification of thymic epithelial malignancies. The map was based on clinical experience and published studies, but it was largely empirical because of limited available data. Dissemination of the map and implementation of a standard thymic stage classification across the world in 2017 have provided more consistent and granular data.

METHODS

More than twice as many cases of node involvement are available for analysis in the current database compared with that of the eighth edition database, allowing validation of many aspects of the eighth edition map. This article details the process and considerations for refinement of the thymic map for the ninth TNM used by the Thymic Domain of the Staging and Prognostic Factors Committee of the International Association for the Study of Lung Cancer. The committee evaluated a large international collaborative data set, published anatomical and clinical studies pertaining to lymph node spread from thymic epithelial tumors, in conjunction with the analysis underlying refinements of the TNM components for the ninth edition TNM classification.

RESULTS

The node map boundaries of the N1 and N2 categories remain unchanged. Visual clarifications have been added to the nomenclature of nodal stations within these regions.

CONCLUSIONS

On the basis of the recommendation to keep the N component unchanged for the ninth edition TNM classification, the lymph node map remains unchanged as well; however, clarifications have been added to facilitate clinical use.

Clinicopathological features and current treatment outcomes of neuroendocrine thymic tumours

OBJECTIVES

Neuroendocrine thymic tumours (NETTs) are a distinct subgroup of rare malignancies. An international, multicentre retrospective analysis was used to study the clinicopathological features, current pattern of diagnosis, treatment and outcomes of patients with NETT.

METHODS

One hundred and forty-six NETT treated from 1989 to 2016 at 21 centres in China, Europe and North America were retrospectively collected and reclassified according to the World Health Organization histological type and International Thymic Malignancy Interest Group (ITMIG)/International Association for Studies in Lung Cancer (IASLC)/Union for International Cancer Control (UICC) staging. Clinicopathological features, diagnostic and therapeutic approaches and outcomes were investigated. Results in the earlier and latter halves of the study period were also compared.

RESULTS

The pretreatment work-up relied exclusively on computed tomography in 85.6% (125/146) of cases. Most patients had advanced disease, with 32.2% (47/146) having lymph node involvement. Higher-grade histological type was associated with more advanced disease (P < 0.05). Induction therapies and surgical procedures were used more often in the latter half of the study. However, the complete resection rate remained unchanged, being 71.5% (98/137) in the whole group. Complete resection was associated with significantly longer 5-year overall survival (77.2% vs 51.2%; P < 0.001) than incomplete or no resection. Significant survival differences were seen with the T, N and M categories of ITMIG/IASLC/UICC staging. Poorly differentiated carcinoma, ITMIG/IASLC/UICC stage IIIa or above and incomplete or no resection were independent risk factors for worse survival. No survival difference was noted between the earlier and the latter halves of the study (58.2% vs 71.9%; P = 0.299).

CONCLUSIONS

Current management similar to that for thymomas is unsatisfactory in providing disease control or long-term survival for patients with NETT. Specific diagnostic tools and novel therapeutic agents are needed to improve management outcomes of this disease.

The safety and efficacy of Cyberknife® for thymic malignancy

PURPOSE

To evaluate the safety and efficacy of Cyberknife® (CK) for the treatment of primary or recurring thymic tumours.

MATERIALS AND METHODS

We retrospectively reviewed 12 patients (16 tumour lesions) with primary or recurring thymic tumours who were treated with CK between March 2008 and October 2017. Their data was stored in prospectively collected database. Kaplan-Meier method was used to calculate survival curves.

RESULTS

Five patients (41.7%), who had inoperable disease or refused surgery, were treated with CK initially, and 7 patients (58.3%) were treated with CK when they had recurrence diseases. The disease sites treated with CK were primary tumour site (5), regional lymph nodes (4), tumour bed (3), chest wall (2), pleura (1), and bone (1). The median target volume was 43.8 cm³ (range, 13.1-302.5cm³) for the 16 tumour lesions. The median follow-up time was 69.3 months (range, 9.7-124.8 months). The median survival time was 48.2 months, and the 5-year and 10-year OS rates were 68.2% and 45.5%, respectively. A high response rate for the tumour lesions irradiated with CK was obtained. Only one patient (8%) experienced in-field recurrence, and the 5-year local recurrence free survival was 90.9%. A case indicated that CK may induce the abscopal effect, which provides the potential to combine CK and immunotherapy. No severe radiation related toxicities were observed, and no treatment related death occurred.

CONCLUSION

CK treatment resulted in good outcomes, particularly local control, with minimal side effects, in highly selected patients with primary and recurring thymic tumours. More studies with larger sample are needed.

Surgical management of thymic epithelial tumors

Resection is the mainstay of treatment for thymic epithelial tumors (TETs), with complete removal of the tumor and involved organs being the ultimate aim. The choice of surgical approach plays a major role in defining treatment success, and the optimal choice of method should thus provide an adequate surgical view to achieve complete tumor resection. While median sternotomy is considered the gold standard for access to the mediastinum, several minimally invasive approaches to thymectomy have been described, including video-assisted robotic-assisted thymectomy, although the oncological outcomes of that procedure remain unclear. A multimodal approach incorporating chemotherapy or chemoradiotherapy followed by extended surgery may improve resectability and outcomes for patients with advanced TETs. Surgical debulking is also reportedly acceptable for invasive thymoma because of its potential for achieving favorable outcomes. Re-resection is an acceptable option for patients with recurrent thymoma after initial resection, and repeat resection for recurrent pleural dissemination seems effective. Here, the literature on current clinical practices in the surgical management and treatment of TETs is reviewed.

Determining extent of invasion and follow-up of thymic epithelial malignancies

Thymic malignancies may exhibit aggressive behavior such as invasion of adjacent structures and involvement of the pleura and pericardium. The role of imaging in the evaluation of primary thymic neoplasms is to properly assess tumor staging, with emphasis on the detection of local invasion and distant spread of disease, correctly identifying candidates for preoperative neoadjuvant therapy. Different imaging modalities are used in the initial investigation of thymic malignancies including chest radiography, computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET), in particular with [18F] fluorodeoxyglucose (FDG). At this moment, CT is the most common imaging modality on the assessment of thymic malignancies. MRI has the benefit of no emission of damaging ionizing radiation reducing the radiation dose to the patient when compared with CT. For this reason, MRI has been playing an important role in the evaluation of tumor invasion and follow up imaging studies which becomes even more relevant in young patients or those patients with prior history of radiation therapy.

Increased Galectin-1 Expression in Thymic Epithelial Tumors

INTRODUCTION

Thymic epithelial tumors (TET) are rare malignancies with a paucity of data on biology and therapeutics. Galectin-1 is a member of the β-galactoside binding protein family and has been shown to mediate tumor growth via modulation of immune cell function. This study examined galectin-1 expression in TET.

PATIENTS AND METHODS

A tissue microarray of 68 patients with TET and 8 benign thymus controls were stained for galectin-1 expression and scored by a pathologist blinded to patient clinical and pathologic data. Galectin-1 expression +1 or greater staining intensity was considered positive. Clinical and pathologic data were abstracted from institutional databases. Expression of galectin-1 in thymic tumor was compared to benign thymus controls and correlated with pertinent clinical and pathologic data.

RESULTS

Galectin-1 expression was higher in TET compared to benign thymus controls (65% vs. 0%). No significant association between galectin-1 expression and the development of recurrent disease, paraneoplastic syndromes, or overall survival was noted.

CONCLUSION

Galectin-1 is overexpressed in the majority of TET. Detection of galectin-1 may differentiate benign from neoplastic thymic processes. Additional studies are needed to assess the role of galectin-1 in the development of TET.

Multimodality therapy for thymoma patients with pleural dissemination

BACKGROUND

Although multidisciplinary treatment is recommended for patients with advanced stage and recurrent thymoma, a detailed treatment strategy remains controversial. We have performed a multimodality therapy of induction chemotherapy (CAMP therapy: cisplatin, doxorubicin, and methylprednisolone) combined with surgery for those patients. We now conducted a retrospective study for investigating the results of this multimodality therapy for thymoma patients with pleural dissemination.

PATIENTS AND METHODS

Between 2003 and 2017, 201 patients underwent surgical resection for thymomas. Twenty-six of them received induction CAMP therapy followed by surgery, and 19 of them with pleural dissemination were enrolled in this study. Those cohort were divided into 2 groups by employing surgical procedures: extrapleural pneumonectomy (EPP) group (n = 10) and resection of plural dissemination (RPD) group (n = 9).

RESULTS

The median age of all patients was 49 years. Based on the WHO classification, the histological diagnoses of those thymomas were as follows: Type B1 (n = 1), Type B2 (n = 13), and Type B3 (n = 5). Seven patients were complicated with myasthenia gravis (MG). Clinical stage of the 13 primary cases based on the Masaoka classification were stage IV, and the remaining six cases had recurrent pleural dissemination after surgery. Partial response in induction CAMP therapy was obtained in 78.9% (n = 15) of the patients. Adverse events (Grade 4) occurred in 2 patients (10.5%). Postoperative complications (Grade 4) were observed in 2 patients (10.5%). In all of the enrolled patients, the five-year overall survival rate (5Y-OS) and 5-year progression-free survival rate (5Y-PFS) were 76.7% and 55.1%, respectively. In the EPP group, 5Y-OS and 5Y-PFS were 83.3% and 83.3%, respectively, and in the RPD group, 70.0% and 29.6%, respectively.

CONCLUSIONS

Multidisciplinary treatment using induction CAMP therapy and surgical resection for thymoma patients with pleural dissemination was effective and feasible. Because of the low recurrent rate of disease, young patients with good cardiopulmonary function and well-controlled MG might be good candidates for EPP.

Surgical resection for advanced thymic malignancy with pulmonary hilar invasion using hemi-clamshell approach

Background

The hemi-clamshell (HCS) approach provides a wide anterior view of the mediastinum as well as outstanding exposure of the pulmonary hilum. Here, we evaluated the utility and outcomes of this approach in cases of advanced thymic malignancy with hilar invasion.

Methods

We performed a retrospective analysis of 14 patients with thymic epithelial malignancy surgically resected with an HCS approach. All required lung resection because of suspected pulmonary hilar vessel invasion.

Results

Histological findings showed that 8 patients had a thymoma and 6 a thymic carcinoma. Thirteen patients underwent lung resection, a lobectomy or bilobectomy in 8 and wedge resection in 5, while 1 had an exploratory thoracotomy. Seven patients with a thymoma underwent resection of disseminated lesions and 8 of 10 who underwent phrenic nerve resection received diaphragmatic plication through an HCS procedure. There were no postoperative mortalities. Macroscopic complete surgical resection was achieved in 13 cases.

Conclusions

An HCS approach was helpful for lung resection performed for advanced thymic malignancy with hilar invasion by providing multiple access paths to the tumor and hilum, allowing for a sufficient surgical margin. Furthermore, it was useful for resection of disseminated lesions and diaphragmatic plication.

Lymph Node Dissection in Thymic Malignancies: Implication of the ITMIG Lymph Node Map, TNM Stage Classification, and Recommendations. J Thorac Oncol. 2016;11:108-114. [PMID: 26762745 DOI: 10.1016/j.jtho.2015.09.001]

OBJECTIVES

The aim of this study is to investigate the pattern of lymphatic metastasis and suggest a lymph node dissection (LND) strategy for thymic malignancies.

METHODS

We retrospectively reviewed 131 thymic malignancy patients who had undergone LND. The recently introduced nodal map of the International Thymic Malignancy Interest Group/International Association for the Study of Lung Cancer and the TNM (tumor, node, metastasis) stage classification were used for grouping and staging the lymph nodes. The pattern of lymphatic metastasis and factors in lymphatic metastasis were investigated.

RESULTS

Node metastasis was detected in 13 patients (N1 in six and N2 in seven). Six N2 patients (86%) had right paratracheal node (RPN) metastases. The rates of node metastasis were 1% at T1 and 37.5% at T2/3 (p < 0.001). The rates of node metastasis were 8% in the M0 and 43% in the M1 (p = 0.03). The rate was higher for thymic carcinoma (25%) than for thymoma (5.1%, p = 0.01), and the rates also differed between the subtypes of thymoma. There was no node metastasis of the A, AB, or B1 types. Tumor size was also a significant factor in node metastasis. The optimal cutoff value for the node metastasis was 6 cm and the specificity was 62%. Only 16% of the patients had received a preoperative histologic diagnosis. All patients with node metastasis had TNM stage II or higher thymic malignancy. The freedom from recurrence rate of the pN1/2 was significantly worse than that of the pN0 (5-year rate 38.5% versus 87.9%, p < 0.001).

CONCLUSION

A status of stage II or higher was the most specific predictor of node metastasis, and the RPN was a crucial station for lymphatic metastasis in thymic malignancies. Thus, LND including RPN is recommended in stage II or higher thymic malignancies.

Minimally Invasive versus Open Thymectomy for Thymic Malignancies: Systematic Review and Meta-Analysis

Complete resection is the standard of care for treatment of thymic malignancies. The use of minimally invasive surgery remains controversial. We searched online databases and identified studies from 1995 to 2014 that compared minimally invasive to open thymectomy for thymic malignancies. Study end points included operative blood loss, operative time, respiratory complications, cardiac complications, length of hospital stay, R0 resection, and recurrence. We summarized outcomes across studies using random-effects meta-analysis to account for study heterogeneity. We calculated ORs for binary outcomes and standardized mean differences for continuous outcomes. We calculated incidence rate ratios for the number of recurrences, accounting for total person-time observed in each study. Of 516 potential reference studies, 30 with a total of 2038 patients met the inclusion criteria. Patients with Masaoka stage I or II thymic malignancy constituted 94.89% of those in the minimally invasive surgery (MIS) group and 78.62% of those in open thymectomy (open) group. Mean tumor size was 4.09 cm (MIS) versus 4.80 (open). Of the 1355 MIS cases, 32 were converted to open cases. Patients in the MIS group had significantly less blood loss; however, no significant differences in operating time, respiratory complications, cardiac complications, or overall complications were identified. Length of stay was shorter for patients in the MIS group. When patients with Masaoka stage I and II thymic malignancy only were analyzed, there was no difference in rate of R0 resection or overall recurrence rate. One postoperative death occurred in the open group. The results of this unadjusted meta-analysis of published reports comparing minimally invasive with open thymectomy suggest that in selected patients with thymic malignancy, minimally invasive thymectomy is safe and can achieve oncologic outcomes similar to those of open thymectomy.

Preoperative induction therapy for locally advanced thymic tumors: a retrospective analysis using the ChART database

BACKGROUND

To evaluate the role of preoperative induction therapy on prognosis of locally advanced thymic malignancies.

METHODS

Between 1994 and 2012, patients received preoperative induction therapies (IT group) in the Chinese Alliance for Research in Thymomas (ChART) database, were compared with those having surgery directly after preoperative evaluation (DS group). All tumors receiving induction therapies were locally advanced (clinically stage III-IV) before treatment and those turned out to be in pathological stage I and II were considered downstaged by induction. Clinical pathological characteristics were retrospectively analyzed. To more accurately study the effect of induction therapies, stage IV patients were then excluded. Only stage I-III tumors in the IT group and stage III cases in the DS group were selected for further comparison in a subgroup analysis.

RESULTS

Only 68 (4%) out of 1,713 patients had induction therapies, with a R0 resection of 67.6%, 5-year recurrence of 44.9%, and 5- and 10-year overall survivals (OS) of 49.7% and 19.9%. Seventeen patients (25%) were downstaged after induction. Significantly more thymomas were downstaged than thymic carcinomas (38.7% vs. 13.9%, P=0.02). Tumors downstaged after induction had significantly higher 5-year OS than those not downstaged (93.8% vs. 35.6%, P=0.013). For the subgroup analysis when stage IV patients were excluded, 5-year OS was 85.2% in the DS group and 68.1% in the IT group (P=0.000), although R0 resection were similar (76.4% vs. 73.3%, P=0.63). However, 5-year OS in tumors downstaged after induction (93.8%) was similar to those in the DS group (85.2%, P=0.438), both significantly higher than those not downstaged after induction (35.6%, P=0.000).

CONCLUSIONS

Preoperative neoadjuvant therapy have been used only occasionally in locally advanced thymic malignances. Effective induction therapy leading to tumor downstaging may be beneficial for potentially unresectable diseases, especially in patients with thymomas. These findings would be helpful to related studies in the future.