Molecular Profiling of Thymoma and Thymic Carcinoma: Genetic Differences and Potential Novel Therapeutic Targets

Correlation of genomic alterations and PD-L1 expression in thymoma

Thymic epithelial tumors (TETs) include several anterior mediastinal malignant tumours: thymomas, thymic carcinomas and thymic neuroendocrine cancers. There is significant variety in the biologic features and clinical course of TETs and many attempts have been made to identify target genes for successful therapy of TETs. Next generation sequencing (NGS) represents a huge advancement in diagnostics and these new molecular technologies revealed that thymic neoplasms have the lowest tumor mutation burden among all adult malignant tumours with a different pattern of molecular aberrations in thymomas and thymic carcinomas. As for the PD-L1 expression in tumor cells in thymoma and thymic carcinoma, it varies a lot in published studies, with findings of PD-L1 expression from 23% to 92% in thymoma and 36% to 100% in thymic carcinoma. When correlated PD-L1 expression with disease stage some controversial results were obtained, with no association with tumor stage in most studies. This is, at least in part, explained by the fact that several diverse PD-L1 immunohistochemical tests were used in each trial, with four different antibodies (SP142, SP263, 22C3, and 28-8), different definition of PD-L1 positivity and cutoff values throughout the studies as well. There is a huge interest in using genomic features to produce predictive genomic-based immunotherapy biomarkers, particularly since recent data suggest that certain tumor-specific genomic alterations, either individually or in combination, appear to influence immune checkpoint activity and better responses as the outcome, so as such in some cancer types they may complement existing biomarkers to improve the selection criteria for immunotherapy.

Pathology of thymoma-where are we today?

Thymoma is the commonest epithelial neoplasm arising from thymus gland. Tumour is slow growing and in the absence of metastasis, surgery is the treatment of choice. Complete resection and bland morphology are important prognostic features. However, a significant proportion of these tumours tend to recur. These recurrent tumours, advanced thymomas and thymic carcinomas require platinum-based combination chemotherapy and radiotherapy. Efforts are being made to explore additional treatment modalities to control disease with the aim of improving survival. Number of thymoma cases worldwide is small in comparison to lung cancers. As a result, fewer studies have been carried out to enhance our understanding of molecular events responsible for the initiation, maintenance, and progression of thymomas. Inspite of this there are advances in understanding the pathology of thymic epithelial neoplasms including genetics, PD-L1 and molecular testing which has bearing on the prognosis, post-surgical management, and testing algorithm. Similar to pulmonary pathology, thymic epithelial tumours will require adequate tumour sampling to carry out ancillary testing. Mutational analytical tests include EGFR, RAS, BRAF, RET, AKT1, PIK3CA and T53 genes. If adequate sample is available (upto100 cells), PD-L1 testing should be considered for immunotherapy in recurrent/ advanced thymomas and thymic carcinomas. This list is likely to expand in future with increasing emphasis on molecular testing to support treatment with newer therapies.

Genomic alterations in thymoma-molecular pathogenesis?

Thymomas and thymic carcinomas (TCs) are neoplasms of thymic epithelial cells. Thymomas exhibit a low mutational burden and a few recurrently mutated genes. The most frequent missense mutation p.(Leu404His) affects the general transcription factor IIi (GTF2I) and is specific for thymic epithelial tumors (TETs). The clinically indolent types A and AB thymomas express the miRNA cluster C19MC. This miRNA cluster known to be the largest in the human genome, is-with expression otherwise restricted mostly to embryonal tissue-silenced in the more aggressive type B thymomas and TCs. Thymomas associated with the autoimmune disease myasthenia gravis (MG) exhibit more frequent gene copy number changes and an increased expression of proteins homologous to molecules that are targets for autoantibodies. TCs, however, display a higher mutational burden, with frequent mutations of TP53 and epigenetic regulatory genes and loss of CDKN2A. The knowledge of molecular alterations in TETs fosters the understanding of their pathogenesis and provides guidance for further studies that may lead to the development of targeted therapies.

Interobserver variation in the classification of thymic lesions including biopsies and resection specimens in an international digital microscopy panel

Aims

Thymic tumours are rare in routine pathology practice. Although the World Health Organization (WHO) classification describes a number of well‐defined categories, the classification remains challenging. The aim of this study was to investigate the reproducibility of the WHO classification among a large group of international pathologists with expertise in thymic pathology and by using whole slide imaging to facilitate rapid diagnostic turnover.

Methods and results

Three hundred and five tumours, consisting of 90 biopsies and 215 resection specimens, were reviewed with a panel‐based virtual microscopy approach by a group of 13 pathologists with expertise in thymic tumours over a period of 6 years. The specimens were classified according to the WHO 2015 classification. The data were subjected to statistical analysis, and interobserver concordance (Fleiss kappa) was calculated. All cases were diagnosed within a time frame of 2 weeks. The overall level of agreement was substantial (κ = 0.6762), and differed slightly between resection specimens (κ = 0.7281) and biopsies (κ = 0.5955). When analysis was limited to thymomas only, and they were grouped according to the European Society for Medical Oncology Clinical Practice Guidelines into B2, B3 versus A, AB, B1 and B3 versus A, AB, B1, B2, the level of agreement decreased slightly (κ = 0.5506 and κ = 0.4929, respectively). Difficulties arose in distinguishing thymoma from thymic carcinoma. Within the thymoma subgroup, difficulties in distinction were seen within the B group.

Conclusions

Agreement in diagnosing thymic lesions is substantial when they are assessed by pathologists with experience of these rare tumours. Digital pathology decreases the turnaround time and facilitates access to what is essentially a multinational resource. This platform provides a template for dealing with rare tumours for which expertise is sparse.

Everolimus in the treatment of metastatic thymic epithelial tumors

INTRODUCTION

There is emerging evidence to support the use of mTOR inhibitor everolimus in patients with advanced, relapsed-refractory thymic epithelial tumors (TETs). However, patient selection and identifying predictive biomarkers of response remains a challenge. Here, we describe a single-center experience with everolimus in patients with TETs and provide detailed molecular analysis of their thymic tumors.

MATERIALS AND METHODS

Data on all patients with advanced TETs who were prescribed everolimus at Stanford University were retrospectively assessed. Time to treatment failure (TTF) and overall survival (OS) were calculated. STAMP, a 130-gene targeted next generation sequencing (NGS) panel, was performed on each tumor sample.

RESULTS

Twelve patients with thymoma (T) and three with thymic carcinoma (TC) treated with everolimus were included. Patients had been heavily pre-treated with an average of three prior lines of therapy. Three patients discontinued treatment due to adverse events. The average TTF was 14.7 months in T and 2.6 months in TC with median OS of 27.6 months in the entire cohort (NR T and 5.3 months TC). Two patients with paraneoplastic autoimmune diseases had improvement in autoimmunity on everolimus. Pathogenic mutations were observed in 4/15 (27 %) of patients and includedTP53, KEAP1 and CDKN2A. Several variants of unknown significance in key genes responsible for modulating tumor response to mTOR inhibition were also found.

CONCLUSION

As previously reported in a prospective trial, patients with previously treated advanced TETs appear to benefit from everolimus in this single institution cohort. Moreover, there was a manageable toxicity profile and no cases of everolimus-induced pneumonitis. A targeted NGS panel revealed several pathogenic mutations but there was no association between detectable tumor mutations and time to treatment failure in this cohort.

A Rare Case of a High-Grade Thymic Squamous Cell Carcinoma Presenting as Cardiac Tamponade

Thymic tumors (for example, thymomas, thymic carcinomas, and thymic neuroendocrine tumors) are rare tumors. Thymic carcinomas are aggressive thymic epithelial neoplasms with a poor prognosis. Cardiac tamponade as a presenting complaint of malignant thymic carcinoma is rare.

A 64-year-old woman presented to the emergency department with complaints of progressive exertional dyspnea and chest discomfort. On physical examination, she had diminished breath sounds at the left lung base. The chest x-ray showed a mediastinal widening, significant cardiomegaly, and pleural effusion. CT scan of the chest revealed a dominant mediastinal mass, left-sided pleural effusion, and pericardial effusion. Transthoracic echocardiogram showed 3 cm circumferential pericardial effusion, with evidence of cardiac tamponade. An emergent pericardiocentesis and thoracentesis were done. A core needle biopsy of the mediastinal mass revealed a high-grade non-keratinizing squamous cell thymic carcinoma. Immunohistochemistry staining was positive for pan-cytokeratin, high molecular weight cytokeratin, CK 5/6, E-cadherin, p63, epithelial membrane antigen (EMA), and BerEp4. The patient had repeated hospital admissions due to recurrent malignant pericardial effusion and left pleural effusion. The patient was planned for radiation and chemotherapy with oncology.

In our review of literature, the primary squamous cell thymic carcinoma presenting initially as a cardiac tamponade was found to be a rare event. Early diagnosis and treatment are of utmost importance given the aggressive clinical course culminating in to poor outcome.

Genomic profiling of thymoma using a targeted high-throughput approach

Introduction

Thymomas and thymic carcinoma (TC) are the most common neoplasms localised in the thymus. These diseases are poorly understood, but progress made in next-generation sequencing (NGS) technology has provided novel data on their molecular pathology.

Material and methods

Genomic DNA was isolated from formalin-fixed paraffin-embedded tumour tissue. We investigated somatic variants in 35 thymoma patients using amplicon-based TruSeq Amplicon Cancer Panel (TSACP) that covers 48 cancer related genes. We also analysed three samples from healthy individuals by TSACP platform and 32 healthy controls using exome sequencing.

Results

The total number of detected variants was 4447, out of which 2906 were in the coding region (median per patient 83, range: 2-300) and 1541 were in the non-coding area (median per patient 44, range: 0-172). We identified four genes, APC, ATM, ERBB4, and SMAD4, having more than 100 protein-changing variants. Additionally, more than 70% of the analysed cases harboured protein-changing variants in SMAD4, APC, ATM, PTEN, KDR, and TP53. Moreover, this study revealed 168 recurrent variants, out of which 15 were shown to be pathogenic. Comparison to controls revealed that the variants we reported in this study were somatic thymoma-specific variants. Additionally, we found that the presence of variants in SMAD4 gene predicted shorter overall survival in thymoma patients.

Conclusions

The most frequently mutated genes in thymoma samples analysed in this study belong to the EGFR, ATM, and TP53 signalling pathways, regulating cell cycle check points, gene expression, and apoptosis. The results of our study complement the knowledge of thymoma molecular pathogenesis.

Programmed death-ligand 1 expression profiling in thymic epithelial cell tumors: Clinicopathological features and quantitative digital image analyses

OBJECTIVES

Whether the extent of expression of programmed death-ligand 1 (PD-L1) is clinically significant remains uncertain, although immuno-oncological features have been studied in thymic epithelial cell tumors (TETs). We investigated the histological features of PD-L1 expression in TETs, and assessed PD-L1 expression using digital image analysis.

MATERIALS AND METHODS

Participants comprised 66 patients with TET who underwent surgical resection between 2001 and 2016. We calculated tumor cell-positive ratio as total proportion score (TPS) with immunohistochemistry using SP263 anti-PD-L1 monoclonal antibody. PD-L1 expression was also quantified using digital image analysis of whole-slide images. We evaluated the relationship between conventional visual TPS using optical microscopy (TPS-V) and TPS from digital image analysis (TPS-IA). We further classified all TETs into high or low PD-L1 expression groups and assessed the clinical significance of PD-L1 expression level using TPS-V and TPS-IA.

RESULTS

WHO histological types were Type A (n = 8), AB (n = 18), B1 (n = 5), B2 (n = 16), B3 (n = 6), metaplastic thymoma (n = 2), and thymic carcinoma (TC) (n = 11). Median TPS-Vs were 2%, 2%, 10 %, 65 %, 90 %, 1%, and 20 %, respectively. TPS-IAs correlated with TPS-Vs in TETs overall and in thymomas, but not in TCs. PD-L1 expression levels in TETs differed significantly among histological types. Whether TPS-V or TPS-IA were used, the PD-L1^high group included more cases of the more aggressive histological types. Recurrence-free survival (RFS) was shorter in the PD-L1^high group than in the PD-L1^low group in thymoma using TPS-IA, whereas RFS of the PD-L1^high group was shorter in all TETs using TPS-V.

CONCLUSION

PD-L1 expression levels depended on the histological type of TET. Extensive PD-L1 expression in TETs was associated with poor prognosis. Digital image analysis is feasible for evaluating PD-L1 expression in TETs and might offer clinically relevant features of thymomas.

PD-L1 expression level in different thymoma stages and thymic carcinoma: a meta-analysis

BACKGROUND

The immune checkpoint ligand, programmed cell death 1 ligand 1 (PD-L1), is expressed in various tumors and associated with response to drugs that target programmed cell death protein 1. Previous studies have estimated the level of PD-L1 expression among different stages of thymoma and thymic carcinoma to evaluate its potential use as a diagnostic factor; however, its varying expression level has been problematic. We conducted this meta-analysis of published literature to evaluate PD-L1 expression in thymomas and thymic carcinomas.

METHODS

We analyzed 12 studies that included 320 patients with type A/AB/B1 thymoma, 225 patients with type B2/B3 thymoma, and 180 patients with thymic carcinoma.

RESULTS

No difference in PD-L1 expression level was found between the B2/B3 vs C groups (odds ratio [OR], 0.67; 95% confidence interval [CI], 0.26, 1.76; p = 0.42). However, the heterogeneity was very high (I² = 78%), and a significant difference was found between groups A/AB/B1 and B2/B3 (OR, 0.22; 95% CI, 0.12, 0.41; p < 0.001), with a relatively low heterogeneity (I² = 55%).

CONCLUSION

PD-L1 positivity might be a useful factor to differentiate type A/AB/B1 thymoma from type B2/B3 and thymic carcinoma. This result might be valuable for potential anti PD-L1 treatment in thymoma and thymic carcinoma.

Thymic cancer in lynch syndrome: an unusual association

Lynch syndrome has been associated with predominantly colorectal, endometrial, and ovarian cancer. We report hereby an unusual case of thymic carcinoma in a patient with Lynch syndrome. A 45-year-old Caucasian woman with a personal history of Lynch syndrome (MLH1 heterozygous mutation) presented with dyspnea, chest pain, and dysphagia. CT chest showed a bulky anterior mediastinal mass, pulmonary nodules, and pericardial effusion. Lung biopsy demonstrated a poorly differentiated carcinoma with squamous features with extensive necrosis, favouring thymic origin. Genomic studies on the tumour revealed deficient mismatch repair status with a two-copy deletion of MLH1 at 3p22.2 and c-Kit mutation. She received carboplatin and paclitaxel, with initial clinical improvement, but then died within 3 months after diagnosis. This case highlights that thymic cancer may be one of the malignancies associated with Lynch syndrome, and MLH1 gene mutation may have a role in the pathogenesis of thymic cancer.

Thymic epithelial tumors: From biology to treatment

In the last few years, meaningful advances have been made in the knowledge of the biology of Thymic Epithelial Tumors (TETs). Data available suggest that in most cases, the different histological subtypes could be distinct biological entities, characterized by specific molecular aberrations, rather than representing a histological continuum of diseases. Recurrent gene mutations in Thymomas and Thymic Carcinoma have been identified, but we still do not know the exact role played by these mutations in TETs pathogenesis. Relevant new data are now available on the pathogenetic mechanisms underlying the association between TETs and autoimmune diseases that warrant further investigations for the potential therapeutic implications. The progress in knowledge of the molecular pathways involved in TETs pathogenesis, allowed to identify and to test target therapies potentially active in such diseases. Platinum-based chemotherapy remains the standard first line treatment for patients with advanced or metastatic TETs. However, some promising data have been reported on the activity of new target therapies, including anti-angiogenic drugs, Cycline Dependent Kinases and PI3K/mTOR inhibitors, as well as of Immune-checkpoint inhibitors. A number of new drugs and combinations are currently under evaluation. The efficacy of new drugs should be balanced with their toxicity profiles, in such complex patients that seem to be more susceptible to develop drug-related toxicities, in particular with immunotherapies.

Next-generation sequencing in thymic epithelial tumors uncovered novel genomic aberration sites and strong correlation between TMB and MSH6 single nucleotide variations

Thymic epithelial tumors (TET) including thymomas and thymic carcinomas are rare, but they are common primary tumors in the anterior mediastinum. The etiology and tumorigenesis of TET remain unclear. To better understand the novel aberrations of this rare tumor and provide more significant mutation sites for targeted therapy, we performed next-generation sequencing detection on 55 patients with TET. Our results showed that most genes in 12 core pathways harbored aberrations of indeterminate potential. In 4 genes (ARID1A, KMT2C, TGFBR2 and MAP3K1), the indel frequency was above 90%. Dozens of genes, including TGFBR2, KMT2C, PRKDC, ATR, CHD2, SDHA, KDM5A, CHEK1, MSH6 and POLE, possessed frameshift indel with different frequencies in different hotspot sites, which could be the new targets of therapy for TET. For the first time, we revealed a strong correlation between the tumor mutational burden and single nucleotide variations, but not frameshift, on DNA mismatch repair gene MSH6 in TET.

Metastatic Thymoma Harboring a Deleterious BRCA2 Mutation Derives Durable Clinical Benefit from Olaparib

Thymomas comprise a group of rare epithelial neoplasms of the anterior mediastinum. Whereas localized disease carries a favorable prognosis, the majority of patients with metastatic thymomas experience progression or recurrence over a 10-year period. Although targeted therapies have become standard of care in many malignancies, no clinically actionable mutations have consistently been identified in metastatic thymomas. Here, we describe a patient with an aggressive thymoma complicated by extensive pleural metastases. Over a 16-year period, she progressed on multiple treatment regimens. To identify additional treatment options, tissue from a pleural metastasis was sent for next-generation sequencing, revealing mutations in BRCA2, tyrosine kinase 2, and SET domain containing 2. Based on supporting evidence for poly (ADP-ribose) polymerase (PARP) inhibition in other BRCA-mutated tumors, the patient was started on the PARP inhibitor olaparib. She derived significant clinical benefit from treatment, with imaging showing overall stabilization of her disease. Here, we review the genotyping results of her tumor and discuss the functional and clinical significance of the mutations in her cancer as well as implications for managing patients with advanced BRCA-mutant thymomas. KEY POINTS: Targeted therapy has yet to enter the standard clinical management of metastatic thymomas. Patients with BRCA2-mutant thymomas may benefit from poly (ADP-ribose) polymerase inhibition.

PD-L1 Expression and Tumor-Infiltrating Lymphocytes in Thymic Epithelial Neoplasms

Thymic epithelial tumors (TETs) are rare malignant mediastinal tumors that are difficult to diagnose and treat. The programmed death 1 (PD-1) receptor and its ligand (PD-L1) are expressed in various malignant tumors and have emerged as potential immunotherapeutic targets. However, the immunobiology of TETs is poorly understood. We evaluated PD-L1 expression and the presence of tumor-infiltrating lymphocytes (CD8 and CD3 expression) in surgical TET specimens from 39 patients via immunohistochemistry and determined their relation to clinicopathological parameters. Cases with membranous reactivity of the PD-L1 antibody in ≥1% of tumor cells were considered positive. Positive PD-L1 expression was observed in 53.9% of cases. Histologically, PD-L1 expression was positive in 2/6 type A, 2/6 type AB, 3/9 type B1, 4/4 type B2, 5/6 type B3, and 5/8 type C TET cases. Thus, the number of cases with PD-L1 expression and the percent expression of PD-L1 were significantly higher in more aggressive thymomas (type B2 or B3). CD3+ and CD8+ tumor-infiltrating lymphocytes were diffusely and abundantly distributed in all cases. These data suggest that a PD-1/PD-L1 blockade is a promising treatment for TETs, with more beneficial treatment effects for aggressive thymomas such as type B2 or B3.

A mutation analysis of the EGFR pathway genes, RAS, EGFR, PIK3CA, AKT1 and BRAF, and TP53 gene in thymic carcinoma and thymoma type A/B3

AIMS

Thymic carcinoma is rare and usually has a fatal outcome. Gene mutations in the epidermal growth factor receptor (EGFR) signalling pathway and TP53 have not been well analysed in thymic carcinoma.

METHODS AND RESULTS

We examined a large cohort of thymic carcinoma and thymoma type A/B3 and looked for gene mutations in the RAS family, EGFR, PIK3CA, AKT1, BRAF and TP53. Among 54 thymic carcinoma cases, RAS family mutations were detected in 10 cases, EGFR in two, PIK3CA in one, AKT1 in one, BRAF in none and TP53 in five. Among 33 thymoma type A/B3 cases, HRAS gene mutation were found in one, PIK3CA in two and AKT1 in one. All these mutations were those of missense type activating mutations. RAS family mutations were significantly more frequent in thymic carcinoma than in thymoma type A/B3 (P = 0.0461). A prognostic analysis focusing on thymic squamous cell carcinoma cases (n = 44) showed that the overall survival was significantly shorter in patients with EGFR pathway mutations (n = 9) than in those without in a univariate analysis (P = 0.0173). Subsequently, EGFR pathway mutations were selected as an independent factor for a poor overall survival in a multivariate analysis (P = 0.0389).

CONCLUSIONS

Mutations in the EGFR pathway and TP53 in thymic carcinoma may be frequent, and the EGFR pathway mutations may be associated with a poor prognosis in thymic squamous cell carcinoma patients. The therapeutic significance of gene mutations in thymic carcinoma should be further clarified.

Deciphering the biology of thymic epithelial tumors

Thymic cancers arise from epithelial cells of the thymus and have a predilection for intrathoracic spread. Clinical behavior varies from relatively indolent to highly aggressive with a capacity to metastasize widely and adversely affect survival. Paraneoplastic autoimmune disorders are frequently observed in association with thymoma and have a significant impact on quality of life. Underlying immune deficits associated with thymic epithelial tumors (TETs) increase the risk for development of opportunistic infections and emergence of extrathymic malignancies. Advances in the molecular characterization of thymic tumors have revealed the lowest tumor mutation burden among all adult cancers and the occurrence of distinct molecular subtypes of these diseases. Mutations in general transcription factor IIi (GTF2I) are unique to TETs and are rarely observed in other malignancies. The infrequency of actionable mutations has created obstacles for the development of biologic therapies and has spurred research to uncover druggable genomic targets. Persistence of autoreactive T cells due to altered thymic function increases the risk for development of severe immune-related toxicity and limits opportunities for use of immune-based therapies, especially in patients with thymoma. In this paper we review emerging data on the molecular characterization and immunobiology of thymic tumors and highlight clinical implications of these discoveries.

Capecitabine and Celecoxib as a Promising Therapy for Thymic Neoplasms

OBJECTIVES

For patients with unresectable or metastatic thymic epithelial neoplasms, few therapy options are available and outcomes are poor. This case series demonstrates that the combination of capecitabine and celecoxib may be a promising therapeutic option for these patients.

MATERIALS AND METHODS

The current report describes the outcomes of 5 patients with thymic neoplasms treated on a drug-drug interaction study of capecitabine and celecoxib in patients with advanced solid malignancies (NCT01705106) conducted at the University of Chicago, plus a sixth patient treated with the same regimen outside of the protocol.

RESULTS

Six patients with thymic neoplasms were treated with capecitabine 1000 mg/m twice daily and celecoxib 200 mg twice daily, day 1 to day 14 on a 21-day cycle. This included 3 patients with thymic carcinoma, 1 with thymic neuroendocrine tumor, and 2 with thymomas. Objective response rates were noted in 3 of 6 patients. Two of the 3 thymic carcinoma patients had complete responses, and the third had a partial response. Best response for the other patients included stable disease for both thymoma patients and progressive disease for the thymic neuroendocrine patient. Other than grade 3 palmar-plantar erythrodysesthesia, which developed in 4 of 6 patients and required dose reductions, the regimen was well tolerated.

CONCLUSIONS

This case series suggests that capecitabine plus celecoxib may be an effective and well-tolerated treatment option for patients with thymic carcinoma. Further studies should be carried out to establish the efficacy of capecitabine plus celecoxib in thymic carcinoma, and to determine whether monotherapy with capecitabine would be similarly effective.

Alteration in gene expression profiles of thymoma: Genetic differences and potential novel targets

BACKGROUND

This study was conducted to investigate the gene expression profiles associated with thymoma to better understand the molecular mechanism underlying the pathogenesis of thymoma.

METHODS

Eight patients with thymomas (type A, AB, B1, and B2) and four controls with thymic cysts were analyzed using microarray profiling to identify changes in gene expression.

RESULTS

Across all of our samples, 2319 messenger RNAs were upregulated and 2776 were downregulated in thymomas relative to thymic cysts. Gene ontology and pathway analyses revealed that a large number of genes participate in cellular functions, among which MHC class II protein complex assembly, assembly with peptide antigen, calcium activated phosphatidylcholine scrambling, and release of cytoplasmic sequestered NF-κB were dysregulated, whereas intestinal immune network for immunoglobulin A production, cytokine-cytokine receptor interaction, the calcium signaling pathway, and pathways related to autoimmune diseases were downregulated.

CONCLUSIONS

Our results revealed gene expression differences between thymomas and thymic cysts, and identified key candidate genes/pathways that might be used as diagnostic markers and potential therapeutic targets to treat cancer metastasis.

A Phase II Study of Pemetrexed in Patients with Recurrent Thymoma and Thymic Carcinoma

INTRODUCTION

Thymoma and thymic carcinoma (TC) are neoplastic diseases with reported chemosensitivity to a broad range of agents. However, because of the rarity of these diseases, few prospective trials have been conducted in patients with advanced thymic malignancies. We conducted a prospective phase II trial to evaluate the clinical activity of pemetrexed, a multitargeted antifolate agent, in previously treated patients with thymoma and TC.

METHODS

A total of 27 previously treated patients (16 with thymoma and 11 with TC) with advanced, unresectable disease were treated with pemetrexed, 500 mg/m², intravenously every 3 weeks for a maximum of six cycles or until undue toxicity or progressive disease. All patients received folic acid, vitamin B₁₂, and steroid prophylaxis.

RESULTS

The median number of cycles administered was 6 (range 1-6). Nine patients with a total of 14 events had grade 3 toxicities; no grade 4 toxicities were noted. In 26 fully evaluable patients, two complete and three partial responses (according to the Response Evaluation Criteria in Solid Tumors) were documented (all in patients with stage IVA thymoma, except for one partial response with stage IVA TC). A total of 14 patients completed the full six cycles of treatment, 7 patients progressed while undergoing therapy, 5 patients discontinued therapy because of intolerance, and 1 patient discontinued therapy because of progressive Morvan syndrome. The median progression-free survival time for all patients was 10.6 months (12.1 months for those with thymoma versus 2.9 months for those with TC). With 23 deaths at data cutoff, the median overall survival time was 28.7 months (46.4 months for those with thymoma versus 9.8 months for those with TC).

CONCLUSIONS

Pemetrexed is an active agent in this heavily pretreated population of patients with recurrent thymic malignancies, especially thymoma.

Elevated CRP levels predict poor outcome and tumor recurrence in patients with thymic epithelial tumors: A pro- and retrospective analysis

Objective

Scarce information exists on the pathogenesis of thymic epithelial tumors (TETs), comprising thymomas, thymic carcinomas (TCs) and neuroendocrine tumors. C-reactive protein (CRP) increases during certain malignancies. We aimed to investigate the clinical relevance of CRP in patients with TETs.

Results

Pretreatment CRP serum concentrations were significantly elevated in patients with TETs, particularly TCs and metastatic TETs. After complete tumor resection CRP serum concentrations were decreased (p = 0.135) but increased significantly in case of tumor recurrence (p = 0.001). High pretreatment CRP was associated with significantly worse 5- and 10-year freedom-from recurrence (FFR) (p = 0.010) and was a negative prognostic factor for FFR (HR 3.30; p = 0.015). IL-6 (not IL-1β) serum concentrations were significantly elevated in patients with TETs but we did not detect CRP tissue expression in TETs.

Materials and Methods

Pretreatment CRP serum concentrations were retrospectively analyzed from 128 surgical patients (1990–2015). In a subset of 68 patients longitudinal analysis of CRP was performed. Additionally, immunohistochemical tumor CRP expression and serum concentrations of interleukin (IL)-6 and IL-1β were measured.

Conclusions

Hence, diagnostic measurement of serum CRP might be useful to indicate highly aggressive TETs and to make doctors consider tumor recurrences during oncological follow-up.

Identification of potential prognostic microRNA biomarkers for predicting survival in patients with hepatocellular carcinoma

Background

The aim of the present study was to identify potential prognostic microRNA (miRNA) biomarkers for hepatocellular carcinoma (HCC) prognosis prediction based on a dataset from The Cancer Genome Atlas (TCGA).

Materials and methods

A miRNA sequencing dataset and corresponding clinical parameters of HCC were obtained from TCGA. Genome-wide univariate Cox regression analysis was used to screen prognostic differentially expressed miRNAs (DEMs), and multivariable Cox regression analysis was used for prognostic signature construction. Comprehensive survival analysis was performed to evaluate the prognostic value of the prognostic signature.

Results

Five miRNAs were regarded as prognostic DEMs and used for prognostic signature construction. The five-DEM prognostic signature performed well in prognosis prediction (adjusted P < 0.0001, adjusted hazard ratio = 2.249, 95% confidence interval =1.491-3.394), and time-dependent receiver-operating characteristic (ROC) analysis showed an area under the curve (AUC) of 0.765, 0.745, 0.725, and 0.687 for 1-, 2-, 3-, and 5-year HCC overall survival (OS) prediction, respectively. Comprehensive survival analysis of the prognostic signature suggests that the risk score model could serve as an independent factor of HCC and perform better in prognosis prediction than other traditional clinical indicators. Functional assessment of the target genes of hsa-mir-139 and hsa-mir-5003 indicates that they were significantly enriched in multiple biological processes and pathways, including cell proliferation and cell migration regulation, pathways in cancer, and the cyclic adenosine monophosphate (cAMP) signaling pathway.

Conclusion

Our study indicates that the novel miRNA expression signature may be a potential prognostic biomarker for HCC patients.

PD-L1 immuno-expression assay in thymomas: Study of 84 cases and review of literature

BACKGROUND AND AIMS

Programmed death ligand 1 (PD-L1), an immune check point inhibitor, is known to be expressed in several malignancies and is being considered as a prognostic factor and a potential immunotherapeutic target. The aim of this study was to characterize PD-L1 expression in thymomas and to determine correlation with clinicopathological features and previously published studies in the literature.

METHODS

Tissue microarrays were prepared from selected blocks of thymomas and immunohistochemistry (IHC) for PD-L1 was performed. Cases were considered as PD-L1 positive or negative depending on whether the percentage of stained thymic epithelial cells were <25 or >25%. Results were compared clinically and with previously published studies using Google and Pubmed search engines.

RESULTS

Of 84 cases of thymoma, 69 (82.1%) revealed PD-L1 positivity in >25% cells. 94.23% of type B thymoma subtypes (B1/B2/B3) were PD-L1 positive (P < 0.001). There was no correlation of PD-L1 with age, gender, myasthenia gravis, the tumor size or stage of disease. Nine studies were available in the literature; most of which showed PD-L1 expression in higher stage and B subtype however percentage positivity varied from 53.7% to over 90%.

CONCLUSIONS

PD-L1 expression is frequent in type B (B1/B2/B3) thymomas. It can be easily evaluated by IHC even on small biopsies in unresectable cases, thereby enabling improved clinical evaluation as well as prognostic stratification of patients. It will serve as a potential indicator for benefit from anti-PD-L1 antibody immunotherapy in thymomas.

GTF2I mutation frequently occurs in more indolent thymic epithelial tumors and predicts better prognosis

OBJECTIVES

A missense mutation in GTF2I was previously identified in thymic epithelioid tumor (TET). However, the clinicopathological relevance of GTF2I mutation has not been illustrated. We studied the prognostic importance of GTF2I mutation as well as its relation to histological subtypes in a large number of TETs.

METHODS

TET samples from 296 patients with clinical and follow-up data were collected, and histological subtypes were classified. Analysis of the GTF2I (chromosome 7 c.74146970T>A) mutation was undertaken by using quantitative real time polymerase chain reaction (qPCR) and direct sequencing. The association of GTF2I mutation with clinicopathological features as well as prognosis was analyzed.

RESULTS

One hundred twenty-four out of 296 (41.9%) patients harbored the GTF2I mutation (chromosome 7 c.74146970T>A). GTF2I mutation was observed in 20 (87.0%) cases of type A thymoma, 70 (78.7%) of type AB thymoma, and the frequency decreased with the degree of histological subtype aggressiveness, with the lowest rate in thymic carcinoma (7.7%). The difference of GTF2I mutation distribution in histological subtypes was statistically significant (p<0.001). The GTF2I mutation was found more frequently in patients with early Masaoka stage (I-II, n=112, 90.3%) than in those with advanced stage (III-IV) disease (n=12, 9.6%, p<0.001). However, only histological subtype significantly predicted the presence of the GTF2I mutation in patients with TETs. The presence of the GTF2I mutation correlated with better prognosis (90.0% compared to 72.0% 5-year survival, and 86% compared to 56% 10-year survival, respectively; log-rank p=0.001). Moreover, it was an independent prognostic factor [hazard ratio (HR), 0.35; 95% confidential interval (CI), 0.15-0.81; p=0.014)].

CONCLUSIONS

The frequency of the GTF2I mutation is higher in more indolent TETs, and correlates with better prognosis. Further studies are required to elucidate the role of the GTF2I mutation in TETs and its clinical application.