Correlation between tumor angiogenesis and invasiveness in thymic epithelial tumors

Evolving treatment landscape in thymic epithelial tumors: From mechanism to therapy

Thymic epithelial tumors (TETs) are rare neoplasms of the anterior mediastinum that arise from thymic epithelial cells. Although surgery is the preferred treatment for resectable TETs, the options for unresectable or recurrent advanced-stage TETs are limited beyond platinum-based chemotherapy. The evolving landscape of TET treatments is marked by significant advancements in targeted therapies and immunotherapies, particularly with anti-angiogenic agents and immune checkpoint inhibitors (ICIs). While monotherapies demonstrated certain efficacy, the development of combination strategies is vital for improving patient outcomes. This review consolidates progress in anti-angiogenic therapies and ICIs, emphasizing the evolution of combination therapies of TETs. Furtherly, we particularly discuss new first-line strategies based on these advancements and emphasizes exploring novel treatments like antibody-drug conjugates, immunomodulatory drugs and cytokine-based agents for TETs. Mechanistically, the molecular features of TETs integrated with clinical diagnosis and targeted therapy, and immunophenotyping of TETs along with its impact on the efficacy and safety of immunotherapy are discussed. Thus, this review systemizes the development in the treatment landscape of TETs, integrating the corresponding molecular and immune mechanisms, aiming to provide new references for the treatment of TETs.

Efficacy and safety of ramucirumab plus carboplatin and paclitaxel in untreated metastatic thymic carcinoma: RELEVENT phase II trial (NCT03921671)

BACKGROUND

Thymic carcinoma (TC) is a rare tumor with aggressive behavior. Chemotherapy with carboplatin plus paclitaxel represents the treatment of choice for advanced disease. Antiangiogenic drugs, including ramucirumab, have shown activity in previously treated patients. The RELEVENT trial was designed to evaluate the activity and safety of ramucirumab plus chemotherapy as first-line treatment in advanced TC.

PATIENTS AND METHODS

This phase II trial was conducted within the Italian TYME network. Eligible patients had treatment-naïve advanced TC. They received ramucirumab, carboplatin and paclitaxel for six cycles, followed by ramucirumab maintenance until disease progression or intolerable toxicity. Primary endpoint was objective response rate (ORR) according to RECIST v1.1 as assessed by the investigator. Secondary endpoints were progression-free survival (PFS), overall survival (OS) and safety. Centralized radiologic review was carried out.

RESULTS

From November 2018 to June 2023, 52 patients were screened and 35 were enrolled. Median age was 60.8 years, 71.4% of patients were male and 85.7% had Masaoka-Koga stage IVB. The Eastern Cooperative Oncology Group performance status was 0 in 68.5% and 1 in 31.4% of patients. At the present analysis carried out some months after the interim analysis (earlier than expected) on 35 patients, ORR was 80.0% [95% confidence interval (CI) 63.1% to 91.6%]. At the centralized radiological review of 33/35 assessable patients, ORR was 57.6% (95% CI 39.2% to 74.5%). After a median follow-up of 31.6 months, median PFS was 18.1 months (95% CI 10.8-52.3 months) and median OS was 43.8 months (95% CI 31.9 months-not reached). Thirty-two out of 35 patients (91.4%) experienced at least one treatment-related adverse event (AE), of which 48.6% were AE ≥ grade 3.

CONCLUSIONS

In previously untreated advanced TC, the addition of ramucirumab to carboplatin and paclitaxel showed the highest activity compared to historical controls, with a manageable safety profile. Despite the small number of patients, given the rarity of the disease, the trial results support the consideration of this combination as first-line treatment in TC.

The Reign of Follistatin in Tumors and Their Microenvironment: Implications for Drug Resistance

Follistatin (FST) is a potent neutralizer of the transforming growth factor-β superfamily and is associated with normal cellular programs and various hallmarks of cancer, such as proliferation, migration, angiogenesis, and immune evasion. The aberrant expression of FST by solid tumors is a well-documented observation, yet how FST influences tumor progression and therapy response remains unclear. The recent surge in omics data has revealed new insights into the molecular foundation underpinning tumor heterogeneity and its microenvironment, offering novel precision medicine-based opportunities to combat cancer. In this review, we discuss these recent FST-centric studies, thereby offering an updated perspective on the protean role of FST isoforms in shaping the complex cellular ecosystem of tumors and in mediating drug resistance.

What Have We Learned from Molecularly Informed Clinical Trials on Thymomas and Thymic Carcinomas-Current Status and Future Directions?

Thymic epithelial tumors (TETs), which include thymomas and thymic carcinomas, are a rare, heterogeneous group of malignancies that originate from the thymus gland. As an important organ of immune cell development, thymic tumors, particularly thymomas, are often associated with paraneoplastic autoimmune disorders. The advances in targeted therapies for both solid and hematologic malignancies have resulted in improved patient outcomes, including better and more durable efficacy and improved toxicity. Targeted therapies have also been investigated in the treatment of TETs, though the results have largely been modest. These have included somatostatin-receptor-targeting therapies, KIT- and EGFR-directed tyrosine kinase inhibitors, epigenetic modulators, anti-angiogenesis agents, and agents targeting the cell proliferation and survival pathways and cell cycle regulators. Numerous investigated treatments have failed or underperformed due to a lack of a strong biomarker of efficacy. Ongoing trials are attempting to expand on previous experiences, including the exploration of effective drugs in early-stage disease. Novel combination therapy strategies are also undergoing evaluation, with the goal of augmenting efficacy and understanding the toxicity while expanding the biomarkers of efficacy and safety. With advances in technology to improve target identification and drug delivery, old targets may become new opportunities, and the subsequently developed drugs may find their place in the treatment of thymic tumors.

Small molecule multitarget antiangiogenic inhibitor treatments for advanced thymic epithelial tumors: A retrospective study

BACKGROUND

Thymic epithelial tumors (TETs) are rare malignant tumors with limited treatment options. No established second-line treatment regimen is available following the preferred first-line chemotherapy, resulting in unsatisfactory efficacy and poor prognosis for patients with advanced TETs. This study aimed to evaluate the efficacy of small molecule multitarget antiangiogenic inhibitors as well as the prognostic factors for advanced TETs.

METHODS

A retrospective study was conducted using data from a real-world database. Clinical information and survival follow-up data were collected from 52 patients with advanced TETs who received small molecule multitarget antiangiogenic inhibitors at Zhejiang Cancer Hospital between August 10, 2016 and August 10, 2022. The short-term efficacy of the treatments, survival time of the patients, and relevant prognostic factors of advanced TETs were analyzed.

RESULTS

Out of the 52 patients included in this study, 16 had thymoma and 36 had thymic carcinoma. The 52 patients had an overall response rate of 21.1% and a disease control rate of 94.2%. In addition, the median progression-free survival (PFS) was 8.05 months, and the overall survival (OS) was 25.00 months. Apatinib was given to 33 patients, anlotinib to 15 patients, and sunitinib or lenvatinib to four patients. Only seven patients received antiangiogenic inhibitors as their first-line therapy, 27 patients as their second-line therapy, and 18 patients as third-line or subsequent therapy. Meanwhile, 42 patients received monotherapy with an antiangiogenesis inhibitor, while 10 patients received combination therapy. Univariate analysis indicated that the combined treatment was associated with a superior OS (p = 0.044); multivariate analysis indicated that the combined treatment was an independent prognostic factor for PFS (p = 0.014) and OS (p = 0.012).

CONCLUSION

The findings suggest that small molecule multitarget antiangiogenic inhibitors are efficacious as second or post-line treatments as a viable alternative treatment option for patients with advanced TETs.

Molecular and Functional Key Features and Oncogenic Drivers in Thymic Carcinomas

Thymic epithelial tumors, comprising thymic carcinomas and thymomas, are rare neoplasms. They differ in histology, prognosis, and association with autoimmune diseases such as myasthenia gravis. Thymomas, but not thymic carcinomas, often harbor GTF2I mutations. Mutations of CDKN2A, TP53, and CDKN2B are the most common thymic carcinomas. The acquisition of mutations in genes that control chromatin modifications and epigenetic regulation occurs in the advanced stages of thymic carcinomas. Anti-angiogenic drugs and immune checkpoint inhibitors targeting the PD-1/PD-L1 axis have shown promising results for the treatment of unresectable tumors. Since thymic carcinomas are frankly aggressive tumors, this report presents insights into their oncogenic drivers, categorized under the established hallmarks of cancer.

An Overview of the Use of Anti-Angiogenic Agents in the Treatment of Thymic Epithelial Tumors

Angiogenesis significantly influences the carcinogenesis of thymic epithelial tumors (TET). Both thymomas and thymic carcinoma (TC) overexpress VEGF-A and VEGFR-1 and -2. This review aims to provide an appraisal of the use of anti-angiogenics in the treatment of TET. The literature research identified 16 studies that were deemed eligible for further analysis. Seven studies assessed the clinical efficacy of sunitinib and five studies the use of apatinib and/or anlotinib. The multicenter Japanese phase II REMORA trial investigated the efficacy of lenvatinib, which is a multi-targeted inhibitor of VEGFR, FGFR, RET, c-Kit, and other kinases. The objective response rate was 38% (25.6-52%), which is the highest documented in TET that progressed after first-line chemotherapy. Anti-angiogenic agents may be useful in the treatment of TET, which are not amenable to curative treatment. Their toxicity profile seems to be acceptable. However, angiogenesis inhibitors do not appear to have a major influence on either thymomas or TC, although multikinase inhibitors may have some effect on TC. The current evidence suggests that the most active agent is lenvatinib, whereas sunitinib could be proposed as an acceptable second-line therapy for TC. Further research concerning the combination of immune checkpoint inhibitors with anti-angiogenic drugs is warranted.

Unraveling molecular networks in thymic epithelial tumors: deciphering the unique signatures

Thymic epithelial tumors (TETs) are a rare and diverse group of neoplasms characterized by distinct molecular signatures. This review delves into the complex molecular networks of TETs, highlighting key aspects such as chromosomal abnormalities, molecular subtypes, aberrant gene mutations and expressions, structural gene rearrangements, and epigenetic changes. Additionally, the influence of the dynamic tumor microenvironment on TET behavior and therapeutic responses is examined. A thorough understanding of these facets elucidates TET pathogenesis, offering avenues for enhancing diagnostic accuracy, refining prognostic assessments, and tailoring targeted therapeutic strategies. Our review underscores the importance of deciphering TETs' unique molecular signatures to advance personalized treatment paradigms and improve patient outcomes. We also discuss future research directions and anticipated challenges in this intriguing field.

Thymic Epithelial Tumors: An Evolving Field

Despite their rarity, thymic epithelial tumors (TETs) have attracted much interest over the years, leading to an impressive number of histological and staging classifications. At present, TETs are divided by the WHO classification into four main subtypes: type A, type AB, and type B thymomas (subdivided into B1, B2, and B3), and thymic carcinomas, going from the more indolent to the most aggressive ones. Among many debated staging proposals, the TNM and the Masaoka-Koga staging systems have been widely accepted and used in routine practice. The four-tiered histological classification is symmetrically mirrored by the molecular subgrouping of TETs, which identifies an A-like and an AB-like cluster, with frequent GTF2I and HRAS mutations; an intermediate B-like cluster, with a T-cell signaling profile; and a carcinoma-like cluster comprising thymic carcinomas with frequent CDKN2A and TP53 alterations and a high tumor molecular burden. Molecular investigations have opened the way to tailored therapies, such as tyrosine kinase inhibitors targeting KIT, mTOR, and VEGFR, and immune-checkpoints that have been adopted as second-line systemic treatments. In this review, we discuss the crucial events that led to the current understanding of TETs, while disclosing the next steps in this intriguing field.

The efficacy of small molecule anti-angiogenic drugs in previously treated Thymic carcinoma

BACKGROUND

Antiangiogenic drugs have shown initial efficacy in the treatment of advanced thymic carcinomas (TCs); however, data are limited. In this study, we provide real-world data relating to the efficacy of antiangiogenic drugs for the treatment of patients with TCs.

METHODS

We retrospectively collected data on clinical progress after first-line chemotherapy in TCs patients who were treated with small molecule antiangiogenic drugs at our institution between January 2010 and December 2021. Tumor response was evaluated according to version 1.1 of the Response Evaluation Criteria in Solid Tumors. Progression free survival and overall survival were calculated using the Kaplan-Meier method.

RESULTS

Of the 17 patients enrolled, 13 (76.5%) received apatinib and four (23.5%) anlotinib monotherapy with an objective response rate of 23.5%. Eleven (64.7%) patients had stable disease. The median follow-up period was 46.0 months (95% confidence interval [CI], 33.0-59.0 months). The median progression survival and overall survival were 7.9 months (95% CI, 6.5-9.3) and 47.0 months (95% CI, 35.4-58.6), respectively. In the 13 patients receiving apatinib, the median PFS was 7.0 months (95% CI, 5.0-9.0), compared with 8.0 months (95% CI, 2.7-13.3 months) for patients in the anlotinib group (P = 0.945). The most common grade 3 adverse events (AEs) were hypertension (n = 3, 23.1%), followed by proteinuria and hand-foot syndrome (HFS, n = 2, 15.4%). There were no grade 4 AEs although eight patients (47.1%) required mid-course discontinuation.

CONCLUSION

For refractory TCs, small molecule antiangiogenic drugs are efficacious as second- or post-line treatments. The toxicity of antiangiogenic therapy is manageable.

Anlotinib in patients with relapsed or refractory thymic epithelial tumors: a study of 50 cases

The optimal pharmaceutical regimen for advanced thymic epithelial tumors (TETs) remains controversial when first-line chemotherapy fails. This retrospective study aims to evaluate the efficacy and safety of anlotinib treatment for patients with relapsed and refractory TETs. Patients with progressive disease after failure of platinum-based chemotherapy were enrolled in this study. Anlotinib was orally taken once a day at an initial dose of 12 mg (10 mg when body weight <60 kg). The cycle was repeated every 3 weeks (2 weeks of treatment followed by 1-week rest). Objective response rate (ORR) and progression-free survival (PFS) were recorded as primary endpoints. There were 50 patients enrolled in this study from October 2018 to June 2021 at a median age of 50 (range 23-79) years old. Patients with thymoma and thymic carcinoma were 33 (66%) and 17 (34%), respectively. The ORR in thymoma and thymic carcinoma patients were 33% (11/33) and 41% (7/17), respectively. The median PFS (mPFS) was 7 (95% CI, 5.9-10.2) months in thymoma patients and 6 (95% CI, 4.6-9.3) months in the thymic carcinoma group. Eleven patients experienced dose reduction due to toxicities, among whom, eight patients discontinued treatment even after dose reduction. Six patients with thymoma showed myasthenia gravis deterioration during treatment, and two of them died of myasthenia gravis crisis. Anlotinib is active in patients with advanced TETs refractory to routine chemotherapy. Prescription of anlotinib to patients with myasthenia gravis should be made cautiously.

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.

Continuous sunitinib schedule in advanced platinum refractory thymic epithelial neoplasms: A retrospective analysis from the ThYmic MalignanciEs (TYME) Italian collaborative group

BACKGROUND

Thymic epithelial tumors (TETs) are rare diseases, with diverse clinical behaviour and prognosis. Intermittent dosing sunitinib represents the gold-standard systemic treatment following platinum-based chemotherapy. To ensure more homogeneous drug exposure, continuous daily dosing (CDD) sunitinib is utilised in other malignancies; however, no data exist in patients with TETs.

METHODS

We retrospectively examined data from patients with platinum-resistant TETs receiving CDD sunitinib 37.5 mg between 1 May 2017 and 31 May 2022 within the Italian collaborative group for ThYmic MalignanciEs. Primary end-points were median progression-free survival, overall response rate (ORR), median duration of response and major treatment-related adverse events.

RESULTS

A total of 20 consecutive patients (12 thymic carcinoma [TC], 6 B3, and 2 B2 thymoma) were evaluated. Among the 19 patients evaluable for response, ORR was 31.6% (95% CI, 12.5%-56.5%). Among patients with TC, one complete response, four partial responses, and four stable diseases were observed (ORR 41%).The overall median progression-free survival was 7.3 months (95% CI, 4.5-10.3): 7.3 months (95% CI, 4.4-NA) within patients with thymoma and 6.8 months (95% CI, 2.8-10.3) in patients with TC; median duration of response was 10.3 months (95% CI, 2.8-NA). CDD was associated with a manageable toxicity profile. Six patients (30%) experienced >G2 toxicity, nine required dose reduction and three discontinued treatment due to adverse events.

CONCLUSIONS

CDD sunitinib showed a relevant antitumor activity and confirmed a good toxicity profile. Similar effectiveness and a better toxicity profile as compared with intermittent dosing historical data suggest that this schedule should be considered.

Investigational drugs for the treatment of thymic cancer: a focus on phase 1 and 2 clinical trials

INTRODUCTION

Thymic epithelial tumors (TETs) are rare tumors of thymic epithelial cells. Treatment options for advanced disease patients who failed standard platinum-based chemotherapy are limited.

AREAS COVERED

Phase I and II trials published in the last five years testing new systemic treatments for advanced TET patients are discussed, as well as ongoing trials. A PubMed database literature review was conducted for articles published between January 2016 and December 2021, and ongoing clinical trials were retrieved from ClinicalTrials.gov database.

EXPERT OPINION

The most promising classes of new drugs in TET patients are angiogenesis inhibitors and immune checkpoint antibodies (ICIs). Sunitinib and Lenvatinib showed response rates of 26% and 38%, respectively, and ICIs showed durable responses in 20-25% in thymic carcinoma patients (TCs). Both approaches are mainly active in TCs, therefore new treatment options for thymomas is an unmet medical need.Two major new therapeutic strategies are ICIs combinations with other drugs and drugs that target pathways that are dysregulated in TETs.Future challenges include the development of preclinical models to help identify novel targets and test new treatment strategies, and randomized clinical trials to provide reliable evidence based on survival endpoints.

Apatinib in patients with recurrent or metastatic thymic epithelial tumor: a single-arm, multicenter, open-label, phase II trial

BACKGROUND

Thymic epithelial tumors (TETs) are rare malignancies and the treatment options are limited. We aimed to evaluate the efficacy and safety of apatinib, an angiogenesis inhibitor, in advanced TETs.

METHODS

This was an open-label, single-arm, phase II trial at three centers in China. Patients with TET who had progressed after failure of at least one line of platinum-based chemotherapy were enrolled. Patients received apatinib 500 mg orally per day. The primary endpoint was objective response rate (ORR). Secondary endpoints were progression-free survival (PFS), overall survival (OS), disease control rate (DCR), and safety.

RESULTS

From June 29, 2017, to April 18, 2019, 25 patients were enrolled. At data cut off (September 30, 2021), one patient achieved complete response, nine achieved partial response, and 11 achieved stable disease, with an ORR of 40% (95% CI 21-61%) and DCR of 84% (95% CI 64-95%). The median PFS was 9.0 (95% CI 5.4-12.6) months. The median OS was 24.0 (95% CI 8.2-39.8) months. All patients reported treatment-related adverse events (TRAEs). Grade 3 TRAEs occurred 26 times in 15 patients. No grade 4 or 5 toxicities occurred.

CONCLUSIONS

This is the first trial of apatinib for the treatment of TETs. Apatinib showed promising antitumor activity and the toxicities were tolerable and manageable.

Clinical and Genetic Characteristics of Thymoma Patients With Autoimmune Hepatitis and Myocarditis

BACKGROUND

Our study investigated a special series of thymoma with autoimmune hepatitis and myocarditis and tried to reveal the gene expression profiles of this series of thymoma.

METHODS

From 2011 to 2019, a total of 13 special thymoma patients presented with autoimmune hepatitis and myocarditis, accounting for about 1.26% of thymoma patients undergoing surgery in Beijing TongRen Hospital. Clinical data were retrospectively collected. All samples were harvested during surgical procedures, and analyzed to identify changes in gene expression using the CapitalBio mRNA microarray analysis, the Whole exome sequencing analysis (WES), qPCR and immunohistochemistry (IHC) tools.

RESULTS

After surgery, patient symptoms were relieved gradually. Levels of lactate dehydrogenase (LDH), creatine kinase MB (CK-MB), aspartate transaminase (AST), and alanine amiotransferase (ALT) increased to some extent within 1 to 3 months after surgery, and fluctuated, and then, gradually decreased close to normal within 6 months after surgery. Enrichment analysis of Kyoto Genome and Genome Encyclopedia (KEGG) pathway was performed and enrichment results were visualized. It indicated that gene expression of 5 signaling pathways, including cell cycle and p53 signaling pathway, were generally abnormal. P53 expression was up-regulated in all tumor tissues. However, IHC and qPCR analysis showed that there was no significant difference in p21 expression between normal and tumor tissue. Results of WES showed that only one driver gene-MDM4 amplified 4 fold in 53.2% thymoma cells. Further qPCR and IHC analysis confirmed the up-regulation of the expression of p53 and mdm4 in 13 thymoma patients with autoimmune hepatitis and myocarditis.

CONCLUSION

Our study reveals the clinical and genetic characteristics of thymoma patients with autoimmune hepatitis and myocarditis. For this special category of thymoma, the up-regulation of p53 and mdm4 plays an important role in the occurrence of thymoma and autoimmune hepatitis/myocarditis.

Resound Trial: A phase 2 study of regorafenib in patients with thymoma (type B2-B3) and thymic carcinoma previously treated with chemotherapy

BACKGROUND

Angiogenesis has an important role in thymic epithelial tumors (TETs). Regorafenib inhibits vascular endothelial growth factor receptors (VEGFRs), platelet-derived growth factor receptor β (PDGFR-β), and fibroblast growth factor receptors (FGFRs). This study explored the activity of regorafenib as monotherapy in patients with advanced or recurrent B2-B3 thymoma (T) and thymic carcinoma (TC) previously treated with platinum-containing chemotherapy.

METHODS

A Fleming single-arm, single-stage, phase 2 trial to evaluate the activity of regorafenib (160 mg once a day by mouth for 3 weeks on/1 week off) was planned. The study was designed to reject the null hypothesis of an 8-week progression-free survival (PFS) rate ≤25% with a type I error of 0.10 and a statistical power of 80% at the alternative hypothesis of an 8-week PFS rate of ≥50% (≥8 of 19 evaluable patients progression-free at 2 months).

RESULTS

From June 2016 to November 2017, 19 patients were enrolled (11T/8TC). We observed partial response (PR) in 1 patient (1T) (5.3%), stable disease (SD) in 14 patients (9T/5TC) (73.7%), and progressive disease in 2 patients (1T/1TC) (10.5%), with a disease control rate of 78.9%. According to Choi-criteria, 13 patients (68.4%) achieved PR, and 2 patients SD (10.5%). The median PFS was 9.6 months whereas median overall survival was 33.8 months. The 8-week PFS rate was 78.9% (15 of 19 patients). Grade 3-4 treatment-related adverse events were observed in 10 patients (52.6%).

CONCLUSIONS

The primary end point of this study was reached. The high rate of PR (Choi-criteria) suggests antitumor activity of regorafenib in TETs. On the basis of survival outcomes, the efficacy of regorafenib should be further evaluated in larger studies.

PECATI: A Multicentric, Open-Label, Single-Arm Phase II Study to Evaluate the Efficacy and Safety of Pembrolizumab and Lenvatinib in Pretreated B3-Thymoma and Thymic Carcinoma Patients

Thymic epithelial tumors are rare neoplastic proliferations of thymic epithelial cells. The aggressiveness of these malignancies increases as higher is the histologic subtype, being thymic carcinoma the most aggressive subtype, with a greater tendency to metastatic spread. In metastatic setting, there is no standard treatment after progression on platinum-based chemotherapy. In this scenario, monotherapy treatment either with lenvatinib, a multi-tyrosine kinase inhibitor with antiangiogenic properties, or pembrolizumab, an immune-checkpoint inhibitor, has reported clinical activity. Potential combination of both agents may have synergistic activity as reported in other cancer types. PECATI trial is a single-arm, investigator-initiated phase II study aiming to assess the activity and safety of the combination of lenvatinib and pembrolizumab in 43 patients with advanced B3-thymoma or thymic carcinoma who progressed on or after at least one previous line of platinum-based chemotherapy. The primary endpoint of the trial is 5-month progression-free survival rate and the secondary endpoints include overall response rate, duration of response, and overall survival.

Molecular landscape of thymic epithelial tumors

Thymic epithelial tumors (TETs) are extremely rare and represent the most frequent tumors of the anterior mediastinum originating from epithelial cells in the thymus. Thymic epithelial tumors include thymomas (TM), thymic carcinomas (TC) and thymic neuroendocrine neoplasms (TNEN). Thymomas are the most predominant and are associated with autoimmune diseases. The available data suggests that the different histological subtypes have specific molecular alterations. Thymic carcinoma shows recurrent gene mutations, but further investigations are needed to understand the role of those mutations in the pathogenetic of the TETs. Some of the new emerging identified molecular alterations have the potential to offer new targeted therapies opening new possibilities for the treatment of thymic epithelial tumors.

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.

Follistatin impacts Tumor Angiogenesis and Outcome in Thymic Epithelial Tumors

Tumor angiogenesis is a key factor in the progression of thymic epithelial tumors (TETs). Activin A, a member of the TGFβ family, and its antagonist Follistatin are involved in several human malignancies and angiogenesis. We investigated Activin A and Follistatin in serum and tumor tissue of patients with TETs in relation to microvessel density (MVD), WHO histology classification, tumor stage and outcome. Membranous Activin A expression was detected in all tumor tissues of TETs, while Follistatin staining was found in tumor nuclei and cytoplasm. Patients with TETs presented with significantly higher Activin A and Follistatin serum concentrations compared to healthy volunteers, respectively. Follistatin serum concentrations correlated significantly with tumor stage and decreased to physiologic values after complete tumor resection. Follistatin serum concentrations correlated further with MVD and were associated with significantly worse freedom from recurrence (FFR). Low numbers of immature tumor vessels represented even an independent worse prognostic factor for FFR at multivariable analysis. To conclude, the Activin A - Follistatin axis is involved in the pathogenesis of TETs. Further study of Follistatin and Activin A in TETs is warranted as the molecules may serve as targets to inhibit tumor angiogenesis and tumor progression.

Optimal management of thymic malignancies: current perspectives

Thymic epithelial tumors (TETs) belong to orphan oncology. The incidence of TETs is about 1.3–3.2 cases per million worldwide. Following pathology, evolution and prognosis are variable. The World Health Organization classification distinguishes thymomas and thymic carcinomas. TETs are composed of thymic epithelial tumoral cells and normal lymphocytes. The mean age at diagnosis is 50–60 years-old. There are no identified risk factors. TETs are frequently associated with paraneoplastic syndromes as myasthenia gravis. The complete R₀ surgical resection is the most significant prognosis factor on survival. In 2010, the French National Institute of Cancer labeled the RYTHMIC network as a specific tumor board including thoracic surgeons, oncologist, and radiation therapist to define standard of care for the management of TETs. The aim of the review was to update knowledge to optimize the standard of care.

Iodine Quantification Using Dual-Energy Computed Tomography for Differentiating Thymic Tumors

The aim of the study was to explore the efficacy of iodine quantification with dual-energy computed tomography (DECT) in differentiating thymoma, thymic carcinoma, and thymic lymphoma.

MATERIALS AND METHODS

Fifty-seven patients with pathologically confirmed low-risk thymoma (n = 16), high-risk thymoma (n = 15), thymic carcinoma (n = 14), and thymic lymphoma (n = 12) underwent chest contrast-enhanced DECT scan were enrolled in this study. Tumor DECT parameters including iodine-related Hounsfield unit (IHU), iodine concentration (IC), mixed HU (MHU), and iodine ratio in dual phase, slope of energy spectral HU curve (λ), and virtual noncontrast (VNC) were compared for differences among 4 groups by one-way analysis of variance. Receiver operating characteristic curve was used to determine the efficacy for differentiating the low-risk thymoma from other thymic tumor by defined parameters.

RESULTS

According to quantitative analysis, dual-phase IHU, IC, and MHU values in patients with low-risk thymoma were significantly increased compared with patients with high-risk thymoma, thymic carcinoma, and thymic lymphoma (P < 0.05/4).The venous phase IHU value yielded the highest performance with area under the curve of 0.893, 75.0% sensitivity, and 89.7% specificity for differentiating the low-risk thymomas from high-risk thymomas or thymic carcinoma at the cutoff value of 34.3 HU. When differentiating low-risk thymomas from thymic lymphoma, the venous phase IC value obtained the highest diagnostic efficacy with the area under the curve of 0.969, and sensitivity, specificity, and cutoff value were 87.5%, 100.0%, and 1.25 mg/mL, respectively.

CONCLUSIONS

Iodine quantification with DECT may be useful for differentiating the low-risk thymomas from other thymic tumors.

Contrast-enhanced ultrasonography characteristics of intrathoracic mass lesions in 36 dogs and 24 cats

Contrast‐enhanced ultrasonography (CEUS) is increasingly available for veterinary patients, however limited studies describe the use of this method for characterizing intrathoracic mass lesions. The aim of this prospective, observational study was to describe CEUS enhancement patterns for intrathoracic mass lesions in a sample of cats and dogs. Sixty patients (36 dogs, 24 cats) were included. Standardized CEUS examinations were performed for 41 pulmonary masses (68%) and 19 mediastinal masses (32%). Final diagnosis was based on cytology and/or histopathology. Absolute time to enhancement (TTE) values were recorded for the intrathoracic mass lesions and spleen. The spleen was used as a reference parenchymal organ to calculate relative TTE (rTTE) values. Absolute TTE of the spleen and intrathoracic mass lesions differed for dogs and cats (P = 0.001). The rTTE values significantly differed between lesions of neoplastic versus non‐neoplastic origin (P = 0.004). The majority of neoplastic pulmonary masses were supplied by bronchial arteries (63%), while most nonneoplastic pulmonary masses were supplied by pulmonary arteries (78%). The sensitivity and specificity for detecting pulmonary neoplastic masses with rTTE were 63% and 78%, respectively. Enhancement patterns for mediastinal thymomas and lymphomas significantly differed (P = 0.002). Thymomas enhanced heterogeneously in a centripetal pattern (86%), whereas lymphomas typically enhanced uniformly in a centrifugal pattern (75%). Findings indicated that CEUS is a feasible method for characterizing intrathoracic mass lesions in dogs and cats, however, the diagnostic sensitivity for detecting neoplastic pulmonary masses was low.

RELEVENT Trial: Phase II Trial of Ramucirumab, Carboplatin, and Paclitaxel in Previously Untreated Thymic Carcinoma/B3 Thymoma With Area of Carcinoma

Thymic epithelial tumors are rare malignancies. Thymic carcinoma represents about 20% of all thymic epithelial tumors and has aggressive behavior, with a greater tendency to metastatic spread. Thymic carcinoma is often diagnosed in advanced stages for which systemic treatment is the main therapeutic option. The association of chemotherapy and antiangiogenic agents in the first-line setting has never been investigated in this very rare cancer. However, preclinical and clinical evidence has suggested that inhibition of angiogenesis could be beneficial. The RELEVENT trial is a multicenter, open-label, single-arm, phase II study aimed at investigating the activity and safety of ramucirumab combined with paclitaxel and carboplatin in chemotherapy-naive patients affected by thymic carcinoma or B3 thymoma with area of carcinoma. The primary endpoint of the trial is the overall response rate. Progression-free survival, overall survival, and safety are secondary endpoints. Patient-reported outcomes will be collected at each visit. The mutational status of a subset of genes, polymorphisms, and selected micro-RNA expression will be evaluated.

Intravoxel incoherent motion diffusion-weighted MR imaging parameters predict pathological classification in thymic epithelial tumors

We evaluated the performance of intravoxel incoherent motion (IVIM) parameters for preoperatively predicting the subtype and Masaoka stage of thymic epithelial tumors (TETs). Seventy-seven patients with pathologically confirmed TETs underwent a diffusion weighted imaging (DWI) sequence with 9 b values. Differences in the slow diffusion coefficient (D), fast perfusion coefficient (D), and perfusion fraction (f) IVIM parameters, as well as the multi b-value fitted apparent diffusion coefficient (ADC_mb), were compared among patients with low-risk (LRT) and high-risk thymomas (HRT) and thymic carcinomas (TC), and between early stage (stages I and II) and advanced stage (stages III and IV) TET patients. ADC_mb, D, and D values were higher in the LRT group than in the HRT or TC group, but did not differ between the HRT and TC groups. The mean ADC_mb, D, and D values were higher in the early stage TETs group than the advanced stage TETs group. The f values did not differ among the groups. These results suggest that IVIM DWI could be used to preoperatively predict subtype and Masaoka stage in TET patients.

Prognostic factors and genetic markers in thymoma

In this literature review prognostic factors and genetic markers that play a role in the staging of thymomas are discussed. The effect on prognosis of different factors, such as paraneoplastic syndromes, age, gender, classification, capsular invasion and surgical treatment, is evaluated. There is no generally accepted pathological classification of thymomas. More recently developed surgical techniques such as video-assisted or robotic thoracic surgery require longer follow-up times to determine whether they have equal long-term results compared to the classical surgical techniques. Many genetic markers have been described but at the present time no definite guidelines can be provided regarding screening and staging of thymomas.

Prognostic value of immunohistochemical markers in malignant thymic epithelial tumors

BACKGROUND

Thymic epithelial tumors (TET) are rare neoplasms with inconsistent treatment strategies. When researching for molecular pathways to find new therapies, the correlation between specific molecular markers and outcome has only rarely been investigated. The aim of this study was to investigate the correlation between survival, metastatic potential and invasiveness of aggressive subtypes of TET and immunohistochemical markers.

METHODS

Overall survival (OS), disease-free survival (DFS), progression-free survival (PFS) and metastasis-free survival (MFS) of patients with WHO type B2/B3 mixed type thymoma (MT), thymoma type B3 (B3) and thymic carcinoma (TC), undergoing surgery [1998-2013] were determined. Tumor specimens were stained using a tissue microarray (TMA) (CD117, CD5, p63, p40, p21, p27, p53, Bcl-2, Ki67, podoplanin, synaptophysin, PTEN and Pax8). Invasive behavior of primary tumors and the presence of extrathoracic metastases were assessed.

RESULTS

We found in 23 patients included into this study (four MT, ten B3, nine TC) that (I) p21 expression in the cytoplasm significantly correlated with a decrease of OS (P=0.016), PFS (P=0.034) and MFS (P=0.005); (II) MFS was significantly shorter when the combination of p21-low p27-low p53-high was present (P=0.029); and (III) nuclear p27 (P=0.042), Ki-67 (P=0.024) and podoplanin (P=0.05) expression correlated with the presence of extrathoracic metastases.

CONCLUSIONS

The main finding of this study is that cytoplasmic p21 expression negatively influences the outcome of malignant TETs and correlates with metastatic activity. Additionally, selected immunohistochemical markers correlate with the distant metastatic potential of TETs. These results may contribute to the stratification of diagnosis and improvement of treatment strategies for thymic malignancies.

Targeted therapy for thymic epithelial tumors: a new horizon? Review of the literature and two cases reports

Surgical resection remains the cornerstone of therapy for early-stage thymic epithelial tumors (TETs), while in advanced or recurrent forms, a multimodality approach incorporating radiation and chemotherapy is required. Given the absence of effective treatment options for metastatic/refractory TETs and the poor related prognosis, there is a compelling need to identify promising 'drugable' molecular targets. Initial reports of activity from targeted agents in TETs derived from anecdotal cases have been often associated with specific activating mutations. Only in recent years, several agents have been formally investigated into prospective clinical trials, with varying success rates. We reviewed the literature on targeted therapy in TETs along with two cases of thymoma achieving striking responses to sorafenib in combination with lapatinib.

Thymoma and thymic carcinomas

Thymomas (Ts) and thymic carcinomas (TCs) are rare tumours of the mediastinum with an incidence rate of 1.7/million per year in Europe. Histological classification is based on rate of non-malignant-appearing thymic epithelial cells and proportions of lymphocytes (A, AB, B1, B2, B3, and C), while staging system concerns localisation of the involved areas. Surgery is the mainstay of treatment with a 10-year survival of 80%, 78%, 75%, and 42% for stages I, II, III and IV, respectively, with an R0 resection. Radiotherapy has a role in selected cases (stage III patients or R1-2 residual) and platinum-based chemotherapy remains the standard of care for patients with advanced disease. A multimodality approach would be advisable when surgery is not recommended. Since molecular aberrations are poorly understood and few responses are reported, targeted therapies are yet being studied. In this review, we describe key aspects of clinical management for Ts and TCs.

State of the art of genetic alterations in thymic epithelial tumors

The rapid advent of technology in recent years has resulted in a substantial increase in our knowledge of the molecular underpinnings of thymic epithelial tumors. In addition to previously described chromosomal aberrations and alterations in DNA methylation, genome sequencing has helped unravel hitherto unknown mutations in these tumors. Attempts are also being made to develop gene signatures to help in the identification of patients likely to benefit from adjuvant therapy. Some of the recently identified genetic alterations have the potential to serve as targets for biological therapy, thus opening newer avenues for treatment of thymic epithelial tumors and increasing the number of effective options for treatment of recurrent or refractory disease.

Sunitinib in patients with chemotherapy-refractory thymoma and thymic carcinoma: an open-label phase 2 trial

BACKGROUND

No standard treatments are available for advanced thymic epithelial tumours after failure of platinum-based chemotherapy. We investigated the activity of sunitinib, an orally administered tyrosine kinase inhibitor.

METHODS

Between May 15, 2012, and Oct 2, 2013, we did an open-label phase 2 trial in patients with histologically confirmed chemotherapy-refractory thymic epithelial tumours. Patients were eligible if they had disease progression after at least one previous regimen of platinum-containing chemotherapy, an Eastern Cooperative Oncology Group performance status of two or lower, measurable disease, and adequate organ function. Patients received 50 mg of sunitinib orally once a day, in 6-week cycles (ie, 4 weeks of treatment followed by 2 weeks without treatment), until tumour progression or unacceptable toxic effects arose. The primary endpoint was investigator-assessed best tumour response at any point, which we analysed separately in thymoma and thymic carcinoma cohorts. Patients who had received at least one cycle of treatment and had their disease reassessed were included in the analyses of response. The trial was registered with ClinicalTrials.gov, number NCT01621568.

FINDINGS

41 patients were enrolled, 25 with thymic carcinoma and 16 with thymoma. One patient with thymic carcinoma was deemed ineligible after enrolment and did not receive protocol treatment. Of patients who received treatment, one individual with thymic carcinoma was not assessable because she died. Median follow-up on trial was 17 months (IQR 14.0-18.4). Of 23 assessable patients with thymic carcinoma, six (26%, 90% CI 12.1-45.3, 95% CI 10.2-48.4) had partial responses, 15 (65%, 95% CI 42.7-83.6) achieved stable disease, and two (9%, 1.1-28.0) had progressive disease. Of 16 patients with thymoma, one (6%, 95% CI 0.2-30.2) had a partial response, 12 (75%, 47.6-92.7) had stable disease, and three (19%, 4.1-45.7) had progressive disease. The most common grade 3 and 4 treatment-related adverse events were lymphocytopenia (eight [20%] of 40 patients), fatigue (eight [20%]), and oral mucositis (eight [20%]). Five (13%) patients had decreases in left-ventricular ejection fraction, of which three (8%) were grade 3 events. Three (8%) patients died during treatment, including one individual who died of cardiac arrest that was possibly treatment-related.

INTERPRETATION

Sunitinib is active in previously treated patients with thymic carcinoma. Further studies are needed to identify potential biomarkers of activity.

FUNDING

National Cancer Institute (Cancer Therapy Evaluation Program).

Available evidence and new biological perspectives on medical treatment of advanced thymic epithelial tumors

Thymic epithelial tumors (TETs) are rare primary mediastinal tumors arising from thymic epithelium. Their rarity and complexity hinder investigations of their causes and therapy development. Here, we summarize the existing knowledge regarding medical treatment of these tumors, and thoroughly review the known genetic aberrations associated with TETs and the present status of potential biological treatments. Epidermal growth factor receptor (EGFR), stem-cell factor receptor, insulin-like growth factor-1 receptor (IGF1R), and vascular endothelial growth factors (VEGF-A, VEGF-B, and VEGF-2) are overexpressed in TETs. EGFR overexpression in TETs is associated with higher stage, and IGF1R overexpression has poor prognostic value. Data indicate that anti-IGF1R monoclonal antibodies, and inhibitors of angiogenesis, somatostatin receptors, histone deacetylase, mammalian target of rapamycin, and cyclin-dependent kinases may be active against TETs. Continued investigations in this field could lead to advancement of targeted and biological therapies for TETs.

Predicting subtypes of thymic epithelial tumors using CT: new perspective based on a comprehensive analysis of 216 patients

It is highly necessary to identify low versus high risk thymic epithelial tumors (TETs) before operation to guide optimal treatment strategies. Current CT diagnostic parameters could not effectively achieve this goal. We evaluated three parameters of CT scan in a cohort of 216 TETs patients. Parameters of contrast enhancement, risk of aggressiveness, and nodule with fibrous septum were evaluated in low (A, AB) versus high risk (B1, B2, B3 and thymic carcinoma) TETs. Grade of contrast enhancement showed predictive value in classifying low and high risk TETs well. A maximal contrast-enhanced range of 25.5 HU could produce 78.8% sensitivity and 68.5% specificity in determining low risk subtypes. Additionally, risk of aggressiveness parameter was demonstrated to be associated with TETs subtype (r = 0.801, P < 0.001) and may add confidence in determining low versus high risk subtypes. Furthermore, multiple nodule with fibrous septum could suggest subtype AB. Findings from this study support role of studied parameters of CT manifestations in predicting the low and high risk stages of TETs. These findings provide empirical evidence for incorporating these parameters in clinical practice for identifying TETs stage before operation, if validated in additional studies.

[Research status of molecular targeted therapy in thymic epithelial tumors]

In recent years, as the study of molecular mechanism and signal transduction pathways of tumors, molecular target therapy in many solid tumors has made great progress. At present, more and more studies focus on molecular target drugs in thymic epithelial tumors and people have got some experience. Molecular target therapy may be a new therapeutic option for patients of thymic epithelial tumor.

Antitumor activity of sorafenib and imatinib in a patient with thymic carcinoma harboring c-KIT exon 13 missense mutation K642E

We report the case of a man with an advanced nonkeratinizing squamous cell thymic carcinoma harboring c-KIT exon 13 missense mutation K642E. This aberration is rare and has never been described previously in patients with thymic cancers. It has been found in a small number of cases of gastrointestinal stromal tumor and also in several cases of acral and mucosal melanomas. Some of the patients with gastrointestinal stromal tumor or melanoma harboring this rare mutation have had a tumor response when treated with imatinib. In contrast, in our case, the mutation was associated with primary resistance to full doses of imatinib but, at the same time, it was not a cause of resistance to sorafenib.

When a thymic carcinoma "becomes" a GIST

Thymic carcinoma (TC) is a rare intrathoracic malignancy that it can be invasive and refractory to conventional treatment. Comprehensive genomic analysis evidenced a molecularly distinct subset of thymic carcinoma with high prevalence of c-kit mutation, which may behave as a gastrointestinal stromal tumor (GIST). Here, we present a case report of TC with c-Kit mutation, who has relapsed after exposure to multiple lines of combination chemotherapy, but he has shown an impressive and long lasting response to sunitinib after imatinib failure.

Intracaval and intracardiac extension of invasive thymoma complicated by superior and inferior vena cava syndrome

We present a case of an aged male with invasive thymoma that extended into the right atrium and led to superior and inferior vena cava syndrome. The patient initially presented with edema of the face and bilateral lower extremities. Echocardiography revealed a mass within the right atrium. Imaging studies demonstrated an anterior mediastinal tumor that continuously occupied the bilateral brachiocephalic veins, superior vena cava, and right atrium. Pathological diagnosis of the tumor biopsy was highly suspicious of thymoma. Due to the high risk of wide spread of the tumor, treatments including resection of the tumor were impossible. Several days later he died, and an autopsy was performed. The tumor was type B2 thymoma invading bilateral brachiocephalic veins, superior vena cava and right atrium. Multiple tumor emboli within the pulmonary arteries were identified. Direct cause of death was deemed to be tumor strangulation at the tricuspid orifice. In addition to the superior vena cava syndrome, inferior vena cava syndrome including ectasia of the intrahepatic vessels was confirmed along with pericarditis. To our knowledge, this is the first English report of an autopsy case of intracardiac thymoma extension, and a detailed literature review of similar cases is also presented.

Molecular aspects of thymic carcinoma

Thymic carcinomas are tumors of the anterior mediastinum derived from the epithelial cells of the thymic gland. Due to their low incidence they are often investigated in combination with thymomas under the rubric of "thymic epithelial neoplasms" and studies exclusively addressing thymic carcinomas are sparse. Thymic carcinomas are characterized by their histologic variability, often resembling tumors seen in other organ systems. This morphologic variation coupled with their rarity has prevented large scale research of these tumors and little is known about the etiology, biologic behavior or best treatment for thymic carcinoma. In recent years, attempts have been made to investigate the molecular characteristics of these tumors in the hope that molecular profiling can be used to predict the prognosis or lead to the development of new treatment strategies. Herein we provide an overview of the recent advances of the molecular analysis of thymic carcinoma with particular emphasis on the potential use for molecularly targeted therapies.

Long lasting efficacy of sorafenib in a heavily pretreated patient with thymic carcinoma

Thymoma and thymic carcinoma are rare neoplasms of the mediastinum, arising from the epithelial cells of the thymus. While surgical resection is the treatment of choice in early stages, platin-based chemotherapy is mainly used in patients with advanced or metastatic disease; however, the prognosis is poor. Here we present the case of a 54 year old female patient suffering from a CD117-negative thymic carcinoma with widespread metastases. After several courses of different kinds of chemotherapy, finally these approaches failed to be effective. Thus we initiated a treatment with sorafenib, an inhibitor of several receptor tyrosine kinases. The treatment was tolerated very well, and within a few weeks the general condition of the patient improved significantly. A CT-scan, performed 3 months after therapy with sorafenib started, showed a 50 % reduction of tumor size, and this effect lasted for 15 months. When the carcinoma relapsed again, we administered another course of chemotherapy and, because of lacking success, we even tried to use sunitinib. However, the patient died in a septic shock, based on progressive disease. In summary, we present a patient with metastastic thymic carcinoma, in which sorafenib led to a tumor-control for 18 months.